International Journal of Modern Physics B

The formation of gold nanoparticles in mordenites has been studied by the methods of FTIR spectroscopy of adsorbed CO and diffuse reflectance UV-visible spectroscopy. Different states of ionic and metallic gold were detected in the zeolite cavities and on the external surface of the zeolite – Au⁺ and Au³⁺ ions, charged clusters Au_n^δ+, and neutral nanoparticles Au_m. The relative amount of these states depends on the method of sample preparation, type of redox treatment and the SiO₂/Al₂O₃ molar ratio.

We have constructed a magnetron nanocluster ion source by plasma-gas-aggregations. Using the magnetron type nanocluster ion source and TOF mass spectrometer, we measured the mass distribution of boron nanoclusters. In these experiments, we detected nanocluster of while the peaks around these masses cannot be resolved. Although magnetron type nanocluster source is useful tool, it has a weak beam intensity and short lifetime for using as an ion source of nanocluster ion implantation, which is one of the important applications for the nanocluster ion source. For this reason, we are constructing and developing a new nanocluster ion source (waveguide-surfatron nanocluster ion source). The new nanocluster ion source consists a large area plasma ion source and gas aggregation cell instead of present nanocluster ion source configuration (magnetron type nanocluster ion source).

Copper catalysts for complete oxidation of hydrocarbons supported on natural zeolites of different structure and origin were prepared by ion-exchange procedure. The catalytic experiments demonstrate that the temperature of beginning of hydrocarbons conversion is in the range of 170-300 °C, depending on the composition of the catalyst. The complete conversion can be observed for both zeolites, depending (probably) on Si/Al ratio of the zeolite matrix. Different states of the copper have been identified by the methods of UV-VIS and XPS spectroscopies and TPR by hydrogen. Whereas no changes in XRD and ²⁷Al MAS NMR was observed under condition of catalytic runs, that supports conclusion about stability of bulk material, XPS spectroscopy reveals significant altering in surface composition under different treatments due to appearance of complicated nano-species of copper, which are responsible for catalytic activity.

The structural properties and energy ordering of the lowest lying isomers of bimetallic (CuAu)_n and (PtPd)_n, n=5-22 clusters have been investigated by means of density functional theory (DFT) in the generalized gradient approximation (GGA). The initial cluster geometry optimization is performed by using a genetic algorithm with the many body Gupta potential. This technique provide a distribution of the lowest energy cluster structures, that are further reoptimized using the DFT-GGA methodology. The energy ordering of isomers obtained with the Gupta potential does not agree, in general, with the one obtained using DFT-GGA for the two bimetallic clusters investigated. However, the lowest energy strucutures of the (CuAu)_n nanoalloy show icosahedral patterns in agreement with the results obtained with the model potential. For the (PtPd)_n clusters segregation effects are found, where the Pt atoms are forming the cluster core and the Pd atoms are on the cluster surface, in agreement with previous calculations using the many body Gupta potential.

Clusters of C₆₀ fullerenes are (multi)-ionised in collisions with O⁵⁺ projectiles at a collision energy of 100 keV. The dominant fragmentation channels are analysed by time-of-flight mass spectrometry for different cluster size distributions. Singly charged , ions are found to be the dominant fragments, in 25% connected with the loss of one or more C₂-units. This result is explained by the large charge mobility in fullerene clusters. Doubly charged fragments, in form of and , contribute to the observed spectrum with less than 5–10% only and are mainly attributed to the fragmentation of dimers. Singly charged small carbon clusters in the size range n = 7 to 19 are formed with low kinetic energies indicating the importance of thermal dissociation processes. The present experiments confirm earlier conclusions on the charge mobility in fullerene clusters.

The electronic structures of a cluster-simulated edge dislocation core in bcc iron were computed using the discrete variational method of density functional theory Energy calculations show that the iron lattice and the impurity atoms trapped in the core have resistance to the dislocation motion. The ubiquitous P-embrittlement of iron can be explained electronically.

A molecular dynamics model was developed to search for stable copper clusters with up to 60 atoms by Gupts empirical potential based on the second-moment approximation to tight-binding model (TB-SMA). We found that isomers do not emerge until the clusters have more than 7 atoms, getting more for clusters with 30~52 atoms, and the magic number, 13, 19, 23, 26, 28, 32, 38, 43, 46, 49, and 55 have ground clusters with higher symmetry and have few isomers.

A new cluster model of α decay is proposed where the effective potential between α-cluster and daughter nucleus is obtained from the double folding integral of the renormalized M3Y nucleon-nucleon interaction and of the density distributions of α particle and daughter nucleus. Without introducing any extra adjustment on the potential, the new model (named as the density-dependent cluster model) can successfully reproduce the experimental half-lives of α decay within a factor of 3. The model also works well for new superheavy elements which are the current interests of nuclear physics and chemistry.

The reasons for superconductivity enhancement in small metallic grains including hundreds of thousand electrons are investigated by solving the generalized gap equation based on BCS mean field theory. The analysis suggests that the superconductivity enhancement in small metallic grains are the results caused by the pairing correlation and the level statistics in the Gaussian orthogonal ensemble (GOE) and the Gaussian unitary ensemble (GUE).

The high quality GaAs/AlAs superlattice structures are characterized by X-ray double-crystal diffraction. The structure parameters of the superlattice are obtained from the rocking curve. The first and second satellite peaks appear around the main 0th-order peak. The FWHMs of 0th-order peak and GaAs substrate are quite close, showing much higher integrity of the crystal lattice. The superlattice structure period D, GaAs thick-ness L_B and AlAs thickness L_Z can be calculated according to the measured angular distance between the diffraction peaks. The experimental results show that the measured values are the same as the designed results. They are useful for improving the quality of superlattice.

By using Gaussian98 package at BPW91 6-31g(d,p) level combined a genetic algorithm (GA) simulation, we have studied the lowest energy structural and electronic properties of the Al_nN (n=2-13) clusters. The ground-state structures, the charge transfers from Al to N site, HOMO-LUMO gap and the covalent, ionic and metallic nature with cluster size and atomic structure are investigated. Al₇N, Al₉N and Al₁₂N cluster is found particularly stable among the Al_nN clusters.

The 3d transition-metal diborides TiB₂, VB₂ and CrB₂ have been characterized by X-ray absorption near-edge-structure (XANES) spectroscopy at the metal K edges. XANES spectra at the Ti, V and CrK-edges of TiB₂, VB₂ and CrB₂, respectively, show similar spectral features up to an energy of about 70 eV above threshold. These features can be correlated to their specific atomic arrangement and electronic structure via multiple-scattering calculations as a function of the cluster size. Actually the second pre-edge feature is assigned to a transition from the metal 1s core state to the central metal 4p state hybridized with 3d band state of the higher-shell metal atoms. The first weak feature on the rising part of the edge is due to higher-shells multiple scattering contributions, suggesting that the transition features at the metal K-edge XANES of 3d transition-metal diborides are strongly affected by medium or long-range order contributions.

We have investigated the photoinduced transformation of C₆₀ film in air at 300 K by means of Raman scattering spectroscopy and atomic force microscopy (AFM). In the Raman experiments, we have observed a new Raman band at 1426 cm^-1, which is absent in the photoinduced polymerized C₆₀ phase. Furthermore, we have investigated the surface structure of the C₆₀ film with variation of the photo-irradiation time in air by using AFM, and have found some lamella-like structures. We have ascribed the 1426 cm^-1 band and the lamella-like structures to the formation of fragmentary graphite in the surface of C₆₀ film.

We have prepared three C₆₀ polymers under high-temperature and high-pressure conditions, and confirmed them to be orthorhombic (1D), tetragonal and rhombohedral (2D) polymer by XRD method, respectively. The ¹³C MAS NMR spectra of both orthorhombic and rhombohedral polymer have been measured and two resonance peaks observed. One resonance at 73 ppm resulted from the sp³ carbons with an intermolecular bonding, the other at 145 ppm is from the inequivalent sp² carbons on the C₆₀ molecule. For 1D polymer, the fine structure of the main peak at 145 ppm has been analyzed. By simulation of the ¹³C MAS NMR peak shape of the inequivalent carbons, we propose that there exist nine inequivalent carbons on a C₆₀ molecule in the orthorhombic (1D) polymer.

The Fermi energy and the minimum size for silver (Ag) metallic clusters have been investigated by the electronic structure calculations using density functional theory method. The results reveal that the work function of clusters with metallicity has the same value as that of bulk metals. This result is interpreted by the role of localized surface states in a thin layer and furthermore it is deduced that a nonmetal layer exists at the surface of Ag bulk metals and their clusters. This layer-thickness is about the same as the lattice constant and the minimum diameter for metallic clusters is about twice of the layer-thickness.

La_2/3Ca_1/3MnO₃ (LCMO) thin films with the thickness from 4 nm to 50 nm were fabricated by the off-axis magnetron sputtering technique. Single crystal (001) SrTiO₃ (STO), (0001) sapphire (ALO), and (001) yttrium-stabilized ZrO₂ (YSZ) were used as substrates. The surface morphology of thin films was characterized by atomic force microscope (AFM). The surface morphology of the thin films depends on the thickness. Thin films on STO substrates with the thickness less than 20 nm show a wave-like morphology, which indicates a two-dimension growth mode. With the thickness increases, some cracks and grains appear on the surface, which indicates the release of the lattice strain due to the lattice mismatch between the substrate and the films. The morphology became smoother with the thickness more than 30 nm, which indicates the full relaxation in strain for the film. The surface roughness and the average grain size increase with the thickness. The morphology for LCMO grows on ALO and YSZ show a rougher surface than that on STO. The rough surface morphology may indicate the wide metallic-to-insulating transition in transport properties.

La_0.7Ca_0.3MnO₃(LCMO) thin films with the thickness of 50 nm were deposited on (001)-oriented single crystal SrTiO₃(STO), MgO and α-Al₂O₃(ALO) by 90° off-axis radio frequency magnetron sputtering. Grazing incidence X-ray diffraction technique, associated with normal X-ray diffraction, was performed to measure the in-plane lattice parameter and investigate the lattice strain and strain relaxation in LCMO films. The results indicated that critical thickness of strain relaxation is very small, which may be related to large mismatch between film and substrate. The mechanism for strain relaxation in LCMO film is perhaps different from that for tetragonal distortion.

Ab initio calculations of the atomic and electronic structures of Cu_N and Na_N (N = 2 - 22) clusters show similar growth behaviors. These can be characterized into 3 regimes: planar, layered and 3D structures. Atomic structures lead to anomalies in the even-odd alternation behavior of the second order energy difference for N = 16 and 17 in both Cu_N and Na_N. The effects of sp-d hybridization on the atomic and electronic structures of Cu_N clusters are discussed.

Density functional theory(DFT) calculations are performed to study W₅ clusters in their neutral, anionic and cationic charge states. All the possible stable isomers are examined, and the most stable isomers for all these species are found. They are singlet state with D_3h symmetry for W₅, and doublets with C_2v symmetry for both and . Equilibrium geometries, electron affinities and dissociation energies are also de termined. Time-depended DFT is used to calculate the low-lying excited states of W₅. Theoretical assignments for the features in the experimental photoelectron spectra are given. All results obtained are in good agreement with available experimental data.

14-GHz electron cyclotron resonance ion source (ECRIS) at the Heavy Ion Research Facility National Laboratory in Lanzhou has been used to investigate the radiative deexcitation of highly charged Ar¹⁷⁺ and Ar¹⁶⁺ ions as they interact with a molybdenum surface. The interaction of Ar¹⁷⁺ and Ar¹⁶⁺ ions above Mo Metallic Surface has been studied by looking at the X-rays with a Si (Li) detector. ECRIS is used in our work for the first time. As the experimental results, the X-ray spectra of Ar¹⁷⁺ and Ar¹⁶⁺ ions interacting with a Mo metal target have been given. The capture of many electrons by Ar¹⁷⁺ and Ar¹⁶⁺ ions, at low velocities, near a metallic surface, has been studied. Hollow atoms produced in the interaction of highly charged ions with a Mo metallic surface have been observed.

The cross-section ratios R of transfer ionization to single electron capture of Helium atom induced by fluorine ions in the strong-interaction region were measured by means of the position-sensitive-detection and the time-of-flight (TOF) technologies. The velocity and charge state dependence of R were studied. It is found that the R decreases when the 2q/v increases, where q and v are the charge state and velocity of projectile respectively. In this energy region the transfer ionization can be look as Two-Step process that one target electron is captured, and another electron is ionized.

Experimental investigation of Molybdenum L-shell X-ray emission is reported in the collision of highly charged Xe^q+ (q = 26,27,30) ions with Molybdenum surface in the energy range 400 to 600 keV. Based on the X-ray spectra obtained and by the extrapolation of experimental data to the lower incident energy range, a limit was found for the energy of the incident ions. The influence of initial charge state on X-ray emission from the target L-shell was observed. The difference of the initial charge state and electron configuration of the incident ions may lead to observably different contribution to the target atom vacancy production and L-shell X-rays emission. Based on COB model, a simple explanation was presented to interpret the features of the experimental results.

The half-lives of cluster radioactivity (¹⁴C-³⁴Si) are well reproduced by a new formula between half-lives and decay energies. This formula is a natural extension of both the Geiger-Nuttall law and the Viola-Seaborg formula from α-decay to cluster radioactivity. The half-lives of new cluster emitters are predicted based on this formula. These are useful for future experimental researches of cluster radioactivity. The physics related to this formula is analyzed and discussed.

The scattering of He atom from a single CO molecule adsorbed on a smooth metal surface is modeled with an ab initio average potential of He-CO interaction super-imposed on a perfect reflecting flat surface. Integral as well as differential cross sections are obtained from exact quantum mechanical calculations. Rayleigh oscillations are shown to be present in the energy dependence of the integral cross sections. Among many Fraunhoffer and reflection-symmetry oscillations in the differential cross sections, a single peak is identified as the rainbow oscillation. This parameter free calculation can explain the observed integral and differential cross sections better than the previously used hard hemisphere model.

By using the tight-binding molecular dynamics simulations in cluster collisions, we give some evidences of the structures of (Na₉)₂ cluster dimer and (Na₄)₄ cluster tetramer from the dynamical point of view. We show that the (Na₉)₂ and (Na₄)₄ cluster matter may exist as intermediate states and finally decay to compact structure in real collision process. With a technique called "sharp cooling", the stable cluster structures (Na₉)₂ and (Na₄)₄ are brought into being to end. The eigen-mode frequencies of these clusters are obtained with Fourier transform of the velocity auto-correlation function which can characterize their structure properties.

In this talk we first explain the context of a topic called "regularities for many-body systems in the presence of random two-body interactions". Then we discuss the robustness of the α clustering phenomenon in the presence of random two-body interactions. Last, we discuss a clustering picture of fermions in a single-j shell with the J_max pairing interaction.

Based on ab initio self-consistent-field technique and atomic cluster method, the various many-body interactions among atoms in dense helium have been computed. By this way, the static high pressure measurements are perfectly explained. A new simple formula for calculation the total energy is proposed by directly combining the two-body potential with the atomic potential. Over a large volume and temperature range of 7.5~1.74 cm3/mol and 2000~21000K, the equation of state (EOS) of helium is given.

A spin cluster of 3 spin 1/2 particles has been studied as a qubit system. A time dependent magnetic field is applied to control the time evolution of the cluster. The lowest energy level of the cluster has the total spin 1/2 separated far away from the excited states and can be used as a qubit register. The universal 1-qubit logic gate can be constructed from the time evolution operator of the non-autonomous many-body system, and the 6 basic 1-qubit gates can be realized by adjusting the applied time dependent magnetic field. As a many-body system, this qubit system is expected to be robust against the dissipation effect of the thermal radiation fields from the environment.

The X-rays induced in the interaction of highly charged Argon ions with gold surface were investigated. We had altered the projectile kinetic energy from 150keV to about 400keV. The results show that, there is a threshold projectile kinetic energy for this excitation. Combining the colliding theory of classic electrodynamics with the concept of quantized orbits, we crudely give this threshold kinetic energy.

The measurements of spectra with wavelengths from 200nm to 1000nm emitted from solid surfaces excited by highly charged ions(HCIs) are reported. The results show that the spectral line of specimen materials can be excited by HCIs, and when the quantity of electric charge is more than a critical number, the intensity of the excited spectral line will be sharply enhanced. Theoretical analysis gives that, this mutation is tied up with the excitation of the conducting-electron gas plasmon in the metal surface.

The present work is devoted to the study of some properties (size, electronic state, redox properties, interaction with matrix) of gold clusters and nanosized particles in Na-Y zeolite modified by iron. Two methods of iron introduction were applied: wet-impregnation and ion-exchange, which result in different structure and reducibility of iron species. Aggregation of iron species and their probable dissolution during gold deposition in samples prepared by wet-impregnation permits to form new Au, Fe and Au-Fe species in contrast to samples prepared by ion-exchange. The strong interaction of Au with Fe species in Au/Fe-imp/NaY changes noticeably a behavior of gold nanoparticles under heating.

We have examined chemical reactions of small silicon cluster ions for n = 7 - 16 with polar organic molecules M (M = CH₃CN, CD₃OD, C₂H₅CN, and C₂H₅OH). The intensities of the adsorption products for m = 1 and 2 were investigated as a function of n. We found for all polar molecules that the relative intensity of Si_nM⁺ to the unreacted is smaller for n = 11, 13, and 14, that is, the adsorption reactivity is smaller for these n than others. It was also commonly observed that the ion are more intense than neighboring n. We discussed the relationship of the reactivity with the geometrical structures and the stabilities of the bare ions and adsorbed ions, from theoretical calculations based on density functional theory.

By means of sonochemical method, Fe₃O₄ and ZnFe₂O₄ nanocrystallines can be synthesized from FeCl₂/urea and ZnCl₂/FeCl₂/urea in water. The products were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) as well as selected area electron diffraction (SAED). Special attention was paid to the microstructure of the nanocrystallines using high-resolution transmission electron microscopy (HREM). Probable mechanisms for the sonochemical formation of Fe₃O₄ and ZnFe₂O₄ nanocrystallines are discussed.

Ferroelectric nanocrystal powders of SrBi₂Ta₂O₉ (SBT) have been first prepared by a polymerizable complex (PC) route. The bismuth powder, strontium carbonate, and water-soluble tantalum oxalate solution were used as starting materials. Thermal analyses (TGA and DSC), x-ray diffraction (XRD), transmission electron microscopy (TEM), and conventional BET method were explored to characterize the structure, morphology, and specific surface area of PC-derived SBT powders calcined at 500-850 °C. As control samples, SBT powders were also fabricated by metalorganic decomposition (MOD) method. The XRD and TEM results indicate that high pure and well crystalline powders can be obtained at 650 °C with a average size of 50 nm. The PC-derived powder has much larger surface area than MOD-derived powder. The BET value of PC and MOD powder at 750 °C for 2h is 6.7 and 1.5m²/g, respectively. The specific surface area of powder prepared by conventional solid-state reaction is quite low, typically less than 1.5m²/g. Therefore, the feasibility of the polymerizable complex route is demonstrated in the powder synthesis of SBT with large surface area.

We have performed first-principles electronic structural calculations to investigate the nature and origin of ferromagnetism in Ti_1-xCo_xO₂ with cobalt concentrations x being 0.0625 and 0.125 in the interesting experimental range. In x being 0.125, when all possible arrangements of two Co atoms within a large supercell are considered, the clustering of Co atoms at nearst-neighbour Ti sites is energetically preferred. Also the interplay between clustering and exchange interactions in Co-doped anatase TiO₂ is discussed. It is predicted that the exchange coupling constant increases up to a value corresponding to lower Co concentrations by decreasing the distance between Co atoms.

Nanostructured colossal magnetoresistive (CMR) films of La_0.67Ca_0.33MnO₃ (LCMO) were deposited by using pulsed electron deposition technique on anodized aluminum oxide membranes with pores of 50 nm in diameter. The magnetic and electronic transport properties were measured on Quantum Design physics properties measurement system (PPMS) and magnetic properties measurement system (MPMS). The resistance peak temperature (T_P) is about 165 K and the Curie temperature (T_C) is about 260 K. Large magnetoresistance was observed near T_P in these nanostructured LCMO films. Linear I-V curves at different temperatures indicate no electronic tunneling effect. The large difference between T_P and T_C suggests that the nature of the resistance peak is different from that of bulk samples. The physics in these nanostructured films should be interesting to explore the mechanism of CMR effect.

The possibility of a non-collinear magnetic configuration of the Fe₃ microcluster supported on the Ni (001) surface has been investigated. The morphology of the supported cluster has been calculated by means of the modified embedded atom model with quenched molecular dynamics simulations, and the electronic structure for the most stable geometrical configuration has been studied using a self-consistent non-collinear spd tight-binding method parameterised to ab-initio tight-binding linear muffin tin orbital results. Our predictions are compared with previous results for the free-standing Fe₃ microcluster. The influence of the substrate in both the structure and the magnetic properties, particularly the onset of non-collinear magnetism, is discussed in detail.

Magnetic coupling constants J for the complete structures of [Gd(capro)₂(H₂O)₄Cr(CN)₆]^•H₂O (capro represents caprolactam) (a) and trans-[Fe(CN)₄(μ-CN)₂Gd(H₂O)₄(bpy)]^•4H₂O^•1.5bpy (b) have been calculated using hybrid density functional theory (DFT) B3LYP combined with a modified broken symmetry approach (BS). The calculated J value of -0.24 cm^-1 for a is very close to the experimental -0.33 cm^-1. They both show the antiferromagnetic interaction between Gd(III) and Cr(III). For b, although the sign of the calculated J value of 4.24 cm^-1 is different from that of the experimental -0.38 cm^-1, the two values both show the weak magnetic coupling interaction between Gd(III) and Fe(III). The spin density distributions are discussed on the basis of Mulliken population analysis. For complexes a and b, both transition metal (Fe(III) or Cr(III)) and rare earth Gd(III) display a spin polarization effect on the surrounding atoms, where a counteraction of the opposite polarization effects leads to a low spin density on the bridging ligand C1N1. For the compounds Gd(III)-Cr(III) (a) and Gd(III)-Fe(III) (b) in the HS states, Cr(III) has stronger spin polarization influence on the bridging atoms than Fe(III) even causing the positive spin population on the bridging atom N1.

The structural, electronic, and magnetic properties of Pd_n (n = 6, 13) clusters supported on (110) surface of TiO₂ rutile have been studied using ab initio ultrasoft pseudopotential calculations within generalized gradient approximation. The magnetic moments and atomic structures of these clusters have only small changes when soft landed on the oxide surface. The magnetic moments of Pd₁₃ cluster on TiO₂ (110) surface is reduced to 6 μ_B as compared to 8 μ_B for free cluster. Our calculations also show that the adsorption energy differences between various orientations of Pd₁₃ cluster on the surface of the slab are small. Therefore, nearly spherical clusters such as Pd₁₃ can roll and have high mobility. The calculated adsorption energies of Pd₆ and Pd₁₃ on the (110) surface of TiO₂ slab are approximately 2.2 and 2.4 eV, respectively.

Anatase Ti_1-xCo_xO₂ nanoparticles were prepared by a hydrothermal process at 180 °C. Ferromagnetic hysteresis loops of the as-prepared samples were measured at room temperature. The Ti_1-xCo_xO₂ (x = 0.0376) powder shows coercivity up to 700 Oe, which is the highest value reported for anatase Ti_1-xCo_xO₂. X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurement results provided evidence that Co was incorporated into TiO₂ lattice. Combined with the fact that the preparation was carried out in an oxidized environment starting from cobalt (II) in the oxidized state, it is suggested that the homogeneous doping of Co into the lattice of anatase should be responsible for the improvement of coercivity in anatase Ti_1-xCo_xO₂ nanoparticles.

The nonuniform demagnetizing field in rectangular elements and the effect of neighbouring elements were calculated numerically by magnetostatic theory. All elements were 10nm thick and 300 nm wide with varying aspect ratio of 1,2,4. The interelements spacing changes from 100nm to 1100nm. It was found that non-uniformities of demagnetizing field both in magnitude and direction occur in the small elements. When the spacing between elements is larger than 1m we can almost neglect all the magnetostatic interaction between elements. However, for larger element with width of 900nm, the effect from neighboring elements is stronger.

Dependence of magnetic properties on the angles between the applied magnetic field and the normal of the film plane in Co/Pt multilayer with easy magnetization direction perpendicular to the film plane have been studied. The results show that the sample exhibits unusual magnetization behaviors when an external magnetic field applied in different angle to the normal of the sample plane. The remanence decreases and the saturation field increases with increasing the angle, accompanying the magnetization-switching field and the coercivity enhance. These results suggest that the magnetization process in multilayers with perpendicular magnetic anisotropy (PMA) could not be described simply using coherent rotation model for uniaxial anisotropic ferromagnet.

The magnetization of the magnetic multilayers with Fibonacci sequence was studied theoretically. By considering the Zeeman, magnetic anisotropy, bilinear and biquadratic exchange energies in the multiplayer system, the angles of the magnetization between all magnetic layers were calculated numerically by minimizing the magnetic energy. The magnetization curves and hysteresis loops were obtained. By considering the different strengths of biquadratic interaction between the magnetic layers some novel phenomena appears. The magnetization in magnetic sub-layers may rotates reversibly or irreversibly by magnetic field.

A series of NiO-containing Co/Cu/Co spin valves with the thickness Co of 5 nm and Cu of 2 nm were fabricated by magnetron sputtering technique with different growth parameters. NiO layer with the thickness of 40 nm is used as a coupling layer. Magnetoresistance (MR) of the spin valve with NiO layer under the bottom of Co/Cu/Co (BSV) is larger than that of the spin valve with NiO layer at the top of Co/Cu/Co (TSV) at room temperature. The MR values can be improved with decreasing the sputtering rate of copper layer. The studies by in-situ grazing incident X-ray scattering on the annealing temperature dependence of MR show that the decrease of the interface roughness between Co and NiO may increase the MR value, while the decrease of the coupling effect between NiO and Co decreases the MR value.

Co/Co₃O₄ bilayers were fabricated by magnetron sputtering with Co and Co₃O₄ targets. The exchange bias effect was observed at 80K, which was much higher than the N• el temperature of Co₃O₄ (about 40K). X-ray photoelectron spectroscopy results showed that CoO was formed near the Co/Co₃O₄ interface, probably due to diffusion of oxygen atoms. The angular dependence of exchange coupling in Co/Co₃O₄ bilayers could not be satisfied with simple cosine function, and the position of the maximum of exchange bias departed from the FM easy axis. The mechanism including rotatable anisotropy and movement of domain wall in AF was used to explain the experiment results.

The ground state properties and spin-density wave of polymeric Hubbard chains are studied by means of the mean-field theory. It is shown that topological structure of the chain possesses a flat-band structure of the energy band. Our analysis shows that the on- site Coulomb repulsion of electrons in the chain leads to the coexistence of ferromagnetic and antiferromagnetic order, i,e., the ferrimagnetic order. Away from half filling, the system displays magnetic phase separation. Possible experimental realizations are suggested.

Combining the microwave absorption dielectric spectrum experiment with computer simulation, the decay process of free photoelectrons related to shallow electron trap in silver halide microcystal is investigated. It is found that when shallow electron traps exist in silver halide, the free photoelectron decay will be sped up at the beginning, and then slowed down in the subsequent process. Shallow electron traps like a reservoir can store up photoelectrons temporarily, and then release them tardily? which results in lengthening free photoelectron lifetime or decay time and enhancing the efficiency of latent image formation.

Photoluminescence (PL) properties of Er and Si nanocrystals co-doped SiO₂ films are studied in a wide Er concentration range. In the Er concentration range of less than 3 at%, Er³⁺ was excited by the energy transfer from Si nanocrystals. Above this concentration, Si nanocrystals and Er do not exist independently but amorphous or crystallin alloys of Si-Er-O are formed. In this region Er can be excited only by directly absorbed excitation light. The highest PL intensity is observed in the Er concentration range where an amorphous alloy of Si-Er-O is formed.

In this contribution, we present the results of recent experiments with the objective of tailoring the size and shape of gold nanoparticles with nanosecond laser pulses. The technique is based on the size and shape dependent surface plasmon resonance frequencies of metal nanoparticles. In our recent experiments gold nanoparticles were prepared by deposition of atoms on dielectric substrates followed by diffusion and nucleation. This usually results in ensembles of oblate nanoparticles with a broad size and shape distribution. Irradiating the gold particles during growth with nanosecond laser pulses makes it possible to produce nanoparticles with a predetermined axial ratio independent of size. For example, irradiating gold nanoparticles with a photon energy of 1.65 eV during growth stabilizes an axial ratio of a/b = 0.14, a being the short axis and b the long axis of the ellipsoidal nanoparticles. Furthermore, post-growth irradiation permits tailoring the average size of the nanoparticles by laser induced surface diffusion and evaporation of atoms. In principle, it is possible to eliminate all particles of undesired sizes by choosing the appropriate photon energies. We demonstrate that narrowing of the width of the surface plasmon resonance from initially 0.52 eV (half width at half maximum) to 0.2 eV is possible by using a single laser frequency. Combining both methods, i.e. laser irradiation during and after growth, finally results in a narrow size and shape distribution of the particles.

GaN epilayers were grown on Si (111) substrates by MOCVD. The optical properties of the samples under different growth conditions were characterized. The abnormal peaks of excitonic emissions related to cubic-GaN were observed on the samples under improper growth conditions based on the LT PL measurements. Also the peak intensity is much higher than that of hexagonal-GaN. The higher intensity of exciton peaks is attributed to the local quantum well formed between the hexagonal- and cubic-GaN. No exciton peaks of cubic-GaN were found on the sample using the optimal growth conditions.

Au:TiO₂ multilayer composite films were prepared by the method of alternating multitarget magnetron sputtering technique. Samples were annealed afterwards. The surface plasmon resonances of the annealed films are around 700nm. TEM pictures showed the remained layered structure with grown gold particles between the layers. The values of χ⁽³⁾ measured by degenerated four wave mixing (DFWM) are in the order of 10^-7 esu which are one order larger than the previous work. The figure of merit (FOM), χ⁽³⁾/α, is in the order of 10^-12 esu cm. The great improvement of χ⁽³⁾ is assumed to be the result from the enhancement of field localization caused by the metallic/dielectric host multilayer structure.

Wire meshes commonly used as transmission grids in ion optical configurations has certain unavoidable disadvantages. Apart from the loss in transmission, there are small angle deflections while the ions are passing close to the wires. This is important for high resolution time-of-flight mass spectrometry as this effect impairs both the dynamic range and the resolution. The amount of deflection from various commercially available grids are determined from simulation calculations on representative wire grids. Gridless designs of ion optics are becoming more popular in recent times for sophisticated and sensitive measurements. Here we report such a device for time of flight mass spectrometer that also assists in perpendicular ionization. This ion optics together with a gridless ion reflector gives a high time resolution of more than 40000.

The evolution of microstructure of cerium oxide nanoparticles prepared in a sol-gel process was investigated by small-angle X-ray scattering (SAXS) measurements, in which the range of annealing temperature was from 298 K to 973 K in air. It was found that their scattering intensities increased dramatically and was proportional to h^-a as the temperature went up to 873 K. Meanwhile, the average radius of gyration R_g, increased. This suggested that these cerium oxide nanoparticles have self-similar structure behavior or mass fractal structure. When the temperature was higher than 873 K, the feature of the SAXS spectra became identical to that of the sactterers with surface fractal structure rather than the mass fractal structure.

The surface morphology of low-energy deposited Pb cluster films was characterized by TEM observation. The free clusters before arrival on the substrates were considered as liquid droplets and a cooling time was assumed to interpret the final morphology by DDA (deposition-diffusion-aggregation) model. The island radius is related to the cluster beam flux, effective diffusion radius and the cooling time. There appeared a viscous net instead of neck-connections and islands when several layers were deposited. After as-prepared samples were exposed to air, an oxide coating, i.e. a core/shell structure, was formed and it could prevent the Pb core from full oxidation.

We report a novel experimental finding of Te cluster films with fractal structure formed at annealing process and the Monte-Carlo simulation of this process. Te cluster films were prepared by using inert gas condensation method and annealed the sample in situ at 523K under TEM. The fractal patterns were formed because of evaporation when the substrate temperature increased. The simulation results indicate that the morphology of the nanofilm is not changed at first, but with increasing temperature some cavities appear due to evaporation. With further increasing temperature, those cavities are enlarged, then networks, fractal patterns and islands are formed subsequently. The turning point of temperature, at which the system has the fastest evaporating rate, is also obtained. It is predicated that the nanostructural films with special pattern and novel property can be achieved by annealing the cluster film in a controlled manner.

In the present paper, the surface tensions and interfacial energies for pure metals and alloys for different structures were predicted by combining with the evaluated thermodynamic parameters in the framework of the CALPHAD (Calculation of Phase Diagrams) method. It is shown that the calculated results are in good agreement with the existing experimental data. On the basis of the predicted values of surface tension and interfacial energy, the phase stability and phase diagram with nano-size particles can be calculated by considering the Gibbs-Thomson equation. The calculated results for pure Fe indicate that the fcc phase is more stable with the decreasing of size of particles, which is in agreement with the experimental data reported, and the phase diagram with nano-size particle can be calculated.

Two batches of C₆₀ films were grown at different growth rate, using a vacuum deposition technique. X-ray diffraction patterns indicate both films have preferential (111) orientation. We measured their dielectric constant and loss factor from 80K to room temperature, and observed distinct broad and asymmetric loss peaks, attributed to orientational glass transition. The apparent activation energy was determined as 344.4 and 304.8 meV for film A and B respectively, larger than the value 280 meV in bulk C₆₀. Ngai's correlated-state model is used to simulate relaxation spectrum, and the real activation energies were calculated, which agree with the reported activation value in bulk C₆₀ very well. We propose that the structure imperfection have contributed additional dipole correlation interactions, which make the relaxation behavior of our C₆₀ films deviate from that of bulk C₆₀.

Isomerization, pseudo-rotation and phase transition in sodium microclusters Na_n are investigated for several sizes (n=4, 8, and 20) using distance dependent tight-binding molecular dynamics simulations with a particular attention to Na₄.

Phase transformation of BN nanoparticles under high pressure (580~860MPa) and low temperature (270~325°C) hot press conditions was investigated. It was found that the contents of orthorhombic boron nitride (oBN) and cubic boron nitride (cBN) increased with the increase of temperature and the prolonging of hot pressing time under high pressure conditions. At the same time, because of the intergrowth of hBN, oBN and cBN. there are strong interactions among these three phases.

Crystalline 6.8-nm PbTiO₃ (PT) nanoparticles were prepared through a modified solgel method. The samples showed high homogeneity and in orthorhombic phase. We examined the structural and phonon characteristics in PT nanoparticles with various grain sizes, finding that the orthorhombic phase begins to emerge at room temperature when particle size reduces to 11 nm. In the 6.8-nm PT nanoparticles, an orthorhombic-to-tetragonal phase transition at 190°C was detected by recording the Raman spectra as a function of temperature. The thermal properties of PT nanocrystals were also studied, demonstrating that the orthorhombic-to-tetragonal phase transition in the 6.8-nm PT nanoparticles is a second-order phase transition with continuous change in lattice parameter.

The thin films of Co-doped and Co₃O₄-doped dielectric LaAlO₃ (LAO) by co-ablation of magnetic metal Co and dielectric LAO on Pt – Ti – SiO₂ – Si substrates have been prepared by pulsed laser deposition. A significant enhancement of dielectric constant of LAO upon doping of Co and cobalt oxide clusters is observed. Furthermore, modulation of the dielectric constant of the thin films by applying a magnetic field is verified, obviously due to the ferromagnetism of Co metal and Co oxide clusters embedded in the LAO thin films. A series of microstructural and dielectric characterizations on the as-prepared thin films have been performed and the mechanism underlying the dielectric enhancement upon the doping of Co and Co₃O₄ clusters is discussed.

The dielectric property of ZnFe₂O₄ – SiO₂ composite thin films deposited on Pt-Ti-SiO₂-Si substrates, prepared by sol-gel method, are investigated. It is observed that the thin films consist of ZnFe₂O₄ nanoparticles embedded in the matrix of SiO₂. Such a composite structure exhibits a significantly enhanced dielectric constant with respect to SiO₂ thin films without too large dielectric loss enhancement.

In the framework of the time dependent local density approximation the harmonic generation of Na₂ in ultrashort intense pulses is investigated. The coupling between harmonics and plasmons of Na₂ is discussed in detail with two laser frequencies 5.266 eV, which is double the resonance of the plasmon, and 1.124 eV, which is half the frequency of plasmons, and with two different peak intensities. One finds appearance of the third and the fifth harmonic generation at high ponderomotive potential.

The reactions of V⁺ and VO⁺ with methanol have been investigated experimentally by FT-ICR mass spectrometer and theoretically by ab initio calculation. Both V⁺ and VO⁺ exhibit impressive reactivity with methanol. The products distribution of different reaction time indicate that in whole reaction processes methanol is adsorbed one by one, and no more than four methanol molecules can be solved in the first shell of central ion V⁺. The reaction mechanisms have been proposed, and the possible geometrical structures of products are also analyzed by DFT calculations.

In recent years, the physical characteristics of noble metal nanoparticles are of considerable interest to material research. We made an effort to get superlattices of Ag nanoparticles at the air/water interface so as to apply various types of measurement by transferring the formed superlattices to suitable substrates. Basic procedure involved is based on a process recently developed for mercaptosuccinic acid (MSA) modified Au nanoparticles. The MSA protected Ag nanoparticles powder was redispersed in distilled water. HCl was added and the solution was left for several days at room temperature. Small crystallites appeared at the air/liquid interface. The diameter of the nanoparticles constructing the 2D superlattice was found to be larger than the parent nanoparticles.

Amorphous silicon nano-particles embedded in hydrogenated amorphous silicon nitride (a-SiN_x:H) matrix have been prepared using an approach based on the deposition of Si-rich a-SiN_x:H thin films by helicon wave plasma-enhanced chemical vapour deposition (HWP-CVD) technique, which has a characteristic of high plasma density at low working pressure. X-ray photoelectron spectroscopy analysis shows that the silicon atom bonds exist in the Si-Si and Si-N configurations and the amorphous silicon regions appear separately in the Si-rich a-SiN_x:H films. The existence of amorphous silicon nano-particles without any post annealing in the a-SiN_x:H random matrix is confirmed by the image of high-resolution transmission electron microscopy. Through infrared absorption analysis, the formation of the separated amorphous silicon nano-particles structure is closely correlated with the deposition parameters such as low working pressure and Ar dilution in the HWP-CVD process.

ZnSe nanoparticles were synthesized via a simple, effective thermal evaporation method by a vapor phase reaction of Zn and Se powder. Particle characterization was performed by X-ray diffraction (XRD), transmission electron microscopy (TEM). It is found that the higher the growth temperature, the larger the nanoparticles. Obvious blue shift was observed in the photoluminescence (PL) spectra at room temperature with decreasing particle size. Raman spectra of the as-grown ZnSe nanoparticles were compared with that of the bulk ZnSe crystal. Though no obvious peak shift was observed for both the transverse optical (TO) and longitudinal optical (LO) phonon modes within the apparatus spectral resolution, non-symmetrical broadening of the LO phonon mode is obvious, indicating that the phonon lifetime is shorter in ZnSe nanoparticles than in bulk material.

Top and bottom NiO-pinning spin valves, e.g. Ta/NiO/Co/Cu/Co/Ta and Ta/Co/Cu/Co/NiO/Ta multilayers, were investigated extensively. At the same thickness of the Cu layer, the GMR ratio for the bottom one is about 30% larger than that for the top one, which is unambiguously due to the roughness effect at the NiO/Co interface. The roughness of NiO/Co interface of the top NiO-pinning spin valve is much larger than that of the bottom one, which may be due to the deposition sequence. On the other hand, although the preferred orientation of the top NiO-pinning spin valve is more prominent than that of the bottom one, it seems not favorable to the specular reflection effect.

We demonstrate the synthesis of zinc oxide microshells by thermal evaporation of ZnO and Zn powders. X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) observations reveal that the products are ZnO microshells with hollow cores, of which the wall thickness is about several hundred nanometers. The possible growth process is discussed.

Polycrystalline cobalt nanowires, with average diameter of 80 nm and length about 10 μm, were synthesized in the hydrazine hydrate solution at room temperature under magnetic fields. A seed-mediated growth approach was applied. Magnetic fields induced the growth of nanowires via aligned self-assembly of cobalt nanocrystallites. Magnetic measurements showed that the saturation magnetization (Ms) of the cobalt nanowires synthesized under magnetic field was five times larger than that of the samples prepared without magnetic fields; while the coercivity (Hc) of the sample prepared under magnetic fields was half of that of the sample synthesized without magnetic fields. The reasons for the magnetism changes were discussed.

Lead tungstate (PbWO₄) an important inorganic scintillator, was synthesized via a mild sonochemical route from an aqueous solution of lead acetate and sodium tungstate in the presence of complexing agents under ambient air. X-ray diffraction (XRD), transmission electron microscope (TEM) and photoluminescence (PL) were used to characterize the products. The as-prepared PbWO₄ nanocrystals crystallize in a tetragonal structure and have an average crystal size of ca. 10 nm.

Novel distributed Bragg reflectors (DBRs) with 6-pair-GaAs/AlAs short period superlattice for the oxide-confined vertical-cavity surface-emitting lasers (VCSEL) are designed. They are for the VCSEL that emits at 840 nm and is grown with 34-period n-type mirrors, three-quantum-well active region, and 22-period p-type mirrors. In addition, a 35-nm-layer of Al_0.98Ga_0.02As was inserted in the top mirrors for being selectively oxidized. The maximum output power is more than 2 mW with low threshold current of about 2 mA. The fact that the device's threshold current in both CW and pulsed operation depends slightly on the operation temperature shows its higher characteristic temperature (T₀).

Boron nitride nanocrystals have been prepared in a hydrothermal route. The crystalline phases have been identified as cubic boron nitride (cBN) and orthorhombic (oBN) by XRD and FTIR. Further evidences for the formation of cBN have been obtained from microanalysis and composition identification by HRTEM, SAED and EDS.

Size-controlled nanocrystalline silicon (nc-Si) has been prepared from a-SiN_x/a-Si:H/a-SiN_x ( 'a' standing for amorphous) sandwich structures by thermal annealing. Transmission electron microscope analyses show that the mean size and the grain size distribution (GSD) of the nc-Si are controlled by the annealing conditions and the a-Si sublayer thickness. Based on our theoretical model of constrained crystallization, we interpret the phenomena of the growth halt of nc-Si and higher crystallization temperature for the thinner a-Si sublayers. The experimental results show that constrained crystallization method is promising to achieve uniform and high density nc-Si array which can be used in the future nano-devices.

Magnetite chains of spheres with different radii and lengths were prepared by aging ferrous hydroxide gel with 0.2M KNO₃ under different external magnetic fields which induced the ultra-fine magnetite particles to combine into chain structure. The magnetite particle size and the chain length could be adjusted by varying the field intensity. The chains could be deposited on silicon substrates to form aligned structure in magnetic field. The hysteresis loops were measured in different directions by a vibrating sample magnetometer (VSM). The structure and magnetic properties were discussed.

We present in this paper the synthesis of rutile TiO₂ nanorods using an efficient microwave hydrothermal method. The product was characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, and the results indicated the growth of high quality rutile nanorods along the c-axis of rutile TiO₂ and the radial aggregation of them into spherical secondary nanoparticles.

Ferroelectric inverse opals are promising candidates for tunable photonic crystals due to their electro-optical and elasto-optical properties. In this work, inverse opal photonic crystals of (Pb_0.9La_0.1)(Zr_0.65Ti_0.35)O₃ (PLZT) were prepared through a self-assembled template replication procedure on a large area (typically 2cm × 1cm). The annealing process was optimized. The surface and cross-section were studied by a scanning electron microscope (SEM). X-ray Diffraction (XRD) results proved that PLZT in the ferroelectric perovskite phase was obtained. A band gap was observed in the transmission spectra and compared with the theoretical value.

The amorphous alloys of Co₅₀Fe₂₀Cu₂V₈B₂₀ are successfully obtained by using the mechanical alloying technique. The sample is analyzed by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The DSC result of the powder sample milled for 120 h shows a complete amorphous phase and a wide supercooled liquid region (T_x - T_g ≃ 80 K).

Ordered SiO₂ mesoporous materials called SBA were prepared by hydrothermal or sol-gel method through using the surfactants as the template, such as cetytrimethylammonium bromide or triblock copolymer. SBA assembled with some different elements and compounds, including Fe, Bi, and B or Fe₂O₃, B₂O₃ and others by dipping or adding of chelating or coupling agents were prepared to form some composites, which characterized by wide or small angle X-ray diffraction, infrared spectra, N₂ static and kinetic adsorption, high resolution transmission electron microscopy and magnetic intensity instrument, respectively. The assembled α-Fe or α-Fe₂O₃ under different conditions possessed lower magnetic coercive force (Hc), for instance the latter was about 87-117(Hc–10³/4πA*m^-1–Os), but specific saturation magnetization (σs–A*m²*kg^-1) increase by 75.4% as compared with the conventional σ- Fe₂O₃(1765Os) particles. However, the properties of the composites assembled with α- Fe was different from α-Fe₂O₃ as mentioned-above. And the relationship between σs or Os and structure for the assembled systems was discussed. After introduced B and Bi to the mesoporous materials, the composites showed not only existence of Brφnsted acid sites for B, but also improvement of the hydrothermal stability and enhance of the long–range order magnitude.

A numerical study of the pattern formation in a vibrated granular layer is presented. Granules are considered to fill in a rectangular container with its length and width changeable. Other control parameters are the vibration frequency and relative acceleration. By the molecular dynamics simulation, there are rich striped patterns to appear. It is interesting to find that the orientation of the striped patterns is related to the length and width of the container, as well as to the vibration frequency and relative acceleration. In is also found that a transition phase, the hexagon structure, is formed in some intermediate parameters.

Poly (styrene-b-butadiene-b-styrene) (SBS) triblock copolymer templates have been prepared by solvent-induced order-disorder phase transition method. Silver nanoclusters have been deposited onto the SBS copolymer templates by low energy clusters beam deposition (LECBD) method. The microstructures of the template and cluster deposits have been characterized by AFM with tapping-mode. It is shown that the triblock copolymers are self-assembled to form an in-plane cylinder ordered microstructure. In the case of low coverage (<50%), silver nanaoclusters deposited on the template tend to aggregate along with the pattern of the template and coalesce into larger nanoparticles. Optical absorption spectra reveal that the surface plasmon resonance (SPR) of silver nanoclusters deposited on the template occurs at 545nm, being a red shift of ~75nm compared to that silver nanoclusters deposited on the fused quartz substrate.

To find novel aspects of the electronic structures in quantum dots (QD) from a view point of spatial broken symmetry, 3-dimensional-mesh Hartree-Fock-Kohn-Sham (3D-MHFKS) calculations¹ are applied to the interacting electron system of electron number N in a symmetry broken hollow QD. For the case of a square hollow quantum dot confined in square hard wall (HW) potential (SSHQD), the magnetic (B) field dependence of the obtained single particle energy levels and chemical potentials in B-N diagram are shown to have a band like electronic structures over the wide B-field range up to 20T. To clarify the origin of the band like electronic structures in SSHQD, 3D-MHFKS calculations are also applied for the mixed symmetry QD's with a circular hollow in square HW potential (SCHQD) and with a square hollow in circular HW potential (CSHQD).

ZnO nanobamboos and nanowires with diameters of 10–30 nm and lengths of 2–4 μm have been prepared by laser ablation in vacuum with precisely controlled pressure, growth and post-annealing temperature. XRD results show the annealed sample is hexagonal ZnO. Low-magnified TEM observation reveals the annealed sample includes ZnO nanobamboos and nanowires. High resolution TEM image and electron diffraction pattern confirm that the structure of ZnO nanobamboo is regular stacking of Zn and O layers with high crystal quality. The growth direction is determined as along [001] direction (c axis). TEM observations confirm that the formation of bamboo-shape ZnO is due to the stacking fault and cleavage. The bundle of those stacking faults seems to be the origin of the black contrast at the nodes. The uniformity of chemical composition for the nanobamboos is identified by EDS profiles. A strong-narrow UV band centred at 390 nm and a weak-broad green band centred at 515 nm are observed at room temperature in the PL spectrum recorded from the annealed ZnO nanobamboos and nanowires.

Single crystal SnO₂ nanowires with diameters of 20 ~ 100nm have fabricated by the reaction of vapor SnO with the oxygen. Vapor-Solid (VS) mechanism is applied to explain to the growth process. Scan electron microscopy (SEM), Transmission electron microscopy (TEM), Selected area diffraction (SAED) and High resolution transmission electron microscopy (HRTEM) studies show that the SnO₂ nanowires grow along [100] or [010] orientation, which is not in agreement with the symmetry of SnO₂ crystal structure. We prove that the low vapor saturation is the key growth condition of the SnO₂ nanowires which prevents the two dimensional nucleation on the side faces and causes one dimensional large aspect ratio.

Te atoms were loaded into nanochannels of zeolite AFI single crystals. The polarized absorption and Raman scattering spectra were measured. The absorption spectra of Te loaded AFI showed large anisotropic properties. The absorption spectra of E//c deeply depended on the loading density of Te atoms. In low Te loading density, Te was adsorbed into the nanochannels in a dimer form whose absorption peak appeared at ca. 3.5 eV. In high loading density, Te form one dimensional nanowires inside the channels. Nanowire formation causes large anisotropic absorption and changes in the spectral shape.

All the previous contributions on electron-LO phonon interaction in quantum dot structures are based on macroscopic isotropic models. The macroscopic dielectric model taking account of the phonon confinement points out that the interaction strength between electron-hole pair and LO phonon (eh-ph) in semiconductor quantum dots is size-independent that is not in accord with some of the experiment data. In this article, after taking account of the effect of transverse charges of ions, microscopic valence force field model based on group theory is used to evaluate the eh-ph and exciton-LO phonon (ex-ph) interactions in GaAs QDs with scales up to 90Å (containing 16863 ions). It turns out that both the interaction strength of eh-ph and ex-ph are not size-independent but size-sensitive.

Bismuth nanowires with width of 10~20 nm, and length of ~200 nm were rapidly prepared from the reduction of Bi(NO₃)₃•5H₂O by ethylene glycol (EG) in alkaline solution under microwave irradiation for 5 minutes. The product was characterized by XRD, TEM and SAED. The effects of the microwave irradiation, the alkaline solution, and the solvent on the formation of bismuth nanowires were also investigated.

CdSe nanoparticles were prepared by simply mixing Na₂SSeO₃ solution with CdSO₄ solution under [Cd²⁺]/[Se^2-] (Cd/Se) ratio of 1.2 at room temperature. The nanoparticles had an average size of 2.3 nm and showed fairly strong photoluminescence (PL) with a peak at 539 nm. Deposition of cadmium (II) hydrous oxide on the CdSe nanoparticles increased photoluminescence quantum yield from 3.1 to 34.8%, in comparison to Rhodamine 6G aqueous solution. Both of the CdSe nanoparticles and the cadmium (II) hydrous oxide deposited on CdSe nanoparticles were characterized as of cubic structure from XRD data and the electron diffraction (ED) patterns. Also, the reason for the photoluminescence enhancement was simply elucidated.

Microwave hydrothermal method is employed to synthesize Co₃O₄ nanocrystals. Co(OH)₂ from reaction of C₄H₆CoO₄·4H₂O with NaOH aqueous solution is used as starting material. With a fixed hold time of an hour, the results show that high quality Co₃O₄ nanocrystals can be synthesized at 200 °C. Decrease of the hold temperature leads to deteriorated crystallinity and incomplete reaction.

The growth mechanism of coiled carbon whiskers was thoroughly studied. The carbon whiskers were prepared by chemical vapor deposition (CVD) at high temperature (500-650 °C) using acetylene as the carbon source and metal powder as the catalyst. The results show that the shape, diameter and pitch of the coiled carbon whiskers are dependent on the particle size of metal powder: when the sizes of metal powder particles are in the range of tens of microns, carbon whiskers have twisted string shape with diameters between 130 nm and 180 nm and a pitch of 100 to 350 nm. When the diameters of metal powder particles are about several hundred microns, tube shape of carbon whiskers with diameters between 280nm and 350 nm and a pitch between 150nm and 180nm are obtained. The range of temperature for the preparation of coiled carbon whiskers by the CVD method follows Quasi-VLS theory.

We present a detailed theoretical investigation on the transport properties of the one dimensional quantum rings. The Aharonov-Bohm effects under the low-voltage and low-frequency perturbation have been carefully studied. Scattering matrix method is adopted to obtain the ac response at external perturbation. The results show that the dc and ac parts of the conductance are dependent on the incident electron energy, magnetic field strength, and the coupling parameter. Some impressive characteristics of the emittance have also been discussed.

High-quality GaN nanorods with triangular cross section were synthesized via a simple chloride-assisted vapor phase epitaxy method. High-resolution transmission electron microscopic observations show that the synthesized GaN nanorods are single crystal with wurtzite hexagonal structure. Raman and photoluminescence measurements were also carried out to study the optical properties of the as-prepared GaN nanorods, which suggests the potential applications in optoelectronic devices.

We investigate the transmission coefficient and persistent current of periodically arranged Aharonov-Bohm rings coupled to external leads. A general theory of quantum waveguide based on the transfer matrix method is developed and is used to study one-dimensional periodic ring structures. A precise expression for the transmission coefficient is derived. The results show that in the contacted ring case the conduction band electrons give rise to periodically arranged persistent currents in the structure, while the band gap electrons can cause giant persistent currents in the first few loops. We also observe isolated transmission peaks in the periodically arranged rings connected via leads.

A self-substrate method is developed for the synthesis of the novel ZnO tetrapod nanostructures in this work. Electron Microscopy shows that there exists a sudden change in the width of each leg of the tetrapod nanostructures. High-resolution transmission electron microscopy (HRTEM) and Selected area electron diffraction (SAED) reveal that the tetrapod nanostructures have the same growth direction [0001] along each leg. The photoluminescence spectra of the nanostructures have been measured and the ultraviolet emission at 388.5nm and green emission at 504.5nm are observed.

Calculations of structure, dynamics and thermodynamics in molecular science all rely on the underlying potential energy surface (PES). Recent advances allow us to visualise this high-dimensional object in a compact fashion, locate global minima efficiently, and sample multistep pathways to obtain rate constants. These methods have been applied to a wide variety of systems, including clusters, glasses and biomolecules, and enable us to treat dynamics on the experimental timescale and beyond.

Based on the time dependent of local density approximation method, the processes of excitation of sodium clusters by swift highly charged C⁶⁺, C⁴⁺, C²⁺, and C⁺ are studied. The time dependent probabilities of escaped electrons are obtained and the ionization probabilities of the Na₂ are deduced. One finds that, the cluster is strongly ionized by C⁶⁺, and there is only a weak ionization by C⁺.

The thermal stability of fullerene C₂₀, C₂₆, C₃₆ and C₆₀ is studied using Molecular Dynamics (MD) simulation based on Brenner potential in this work. Lindemann's relative root-mean-square (rms) bond-length fluctuation is used to monitor the behavior of the structural and thermal properties. The results show that the rms bond-length fluctuation becomes scattered points at relative high tempereture, which is caused by different isomerization transitions. Larger fullerenes are found to be more stable than small ones. The results are compared with those from MD simulation based on TLHT potential. Mechanic stability of fullerene C₂₀ is also studied.

We present experimental measurements of time-dependent photoelectron spectra observed in thermionic emission of small carbon cluster anions and C₆₀ fullerenes. The combination of photoelectron velocity-map imaging with time-gated detection allowed to resolve delayed electron emission at different stages of the emission process. This unique capability allows us to analyze pure thermionic energy spectra under well-defined conditions. Experimental spectra are analyzed within the framework of the detailed balance theory.

The electron spin decoherence in endohedral fullerene A@C₆₀ is studied at low temperature using master equation under the Markov approximation. At lower magnetic field the polarization decay occurs with form e^-(t/T₁)2 consitent with previous reports having decays of the order of ℏ/A, and the relationship is satisfied. For the case of A@C₆₀ (A =N,P) endohedral fullerenes, the decay times on the order of tens of ns are calculated. For a strong external magnetic field, polarization strongly depends on the external magnetic field, the decay time is suppressed.

In highly charged ion Xe^q+ (q=8, 15, 20, 25, 30) on C₆₀ collisions (v = 0.19 a.u.), the energy loss of projectiles in frontal collisions has been measured by analyzing the kinetic energy of scattered ions. Using singly charged projectiles He⁺, the measurement of the ejected electron number provides information on the electronic energy deposition during the fontal collision on the C₆₀ target.

A statistical mechanical model was used to calculate the curvature of the 5 chemically synthesized DNAs which contain repeats sequences (CCTG)_n · (CAGG)_n and (ATTCT)_n · (AGAAT)_n associated with human diseases. 8% polyacrylamide gel analyses were also performed for these 5 DNAs. The results indicate the curvature of the sequences CCTG/bend and ATTCT/bend are larger than that of the sequences CCTG/straight and ATTCT/straight. The curvature of straight/bend is larger than that of CCTG/straight and ATTCT/straight, and smaller than that of CCTG/bend and ATTCT/bend. There exists good consistent between theoretical prediction and experimental data.

A model based on the concept of clustering damages has been proposed to relate dose absorbed by cell population to the initial biological damages. The key input is the size distribution of ionization clusters formed by ionizing radiation in 3nm diameter sphere (nucleotide) and 10nm diameter sphere (nucleosome) calculated by detailed Monte Carlo simulation code. The clustering damage based model also includes particular bio-geometrical information of cell at different cell cycle point. Some experimental and empirical data were used to transform the ionization cluster size distribution into lethal and potentially lethal cross sections (cell^-1Gy^-1), which are just the input of Lethal and Potentially Lethal (LPL) model. The model enables us to calculate the average number of fatal lesions at long time after irradiation and then surviving probability at different dose level and dose rate for specific kind of radiation characterized by cluster size distribution. To test the model, the surviving curves of V79 cell line at G1 phase and S phase irradiated by 40keV/μm deuteron ion were calculated and acceptable results were obtained.

A new version of two-compartment (TC) model named Revised TC (RTC) model, was proposed by redefining radiation quality factors on the basis of a new concept, clustering clusters, as average number of clusters which can cause repairable and irreparable damages (i.e., two compartments) in a cell nucleus at unit absorbed dose, respectively. The model parameters were calibrated by measured survival fractions of V79 cells at G1/S and late-S phases irradiated by 20 and 40 keV/μm deuterons and 127keV/μm ³He ions. The initial slopes of survival fraction for V79 cells irradiated by proton and alpha particles of different LET ranging from 10 to 230 keV/μm at G1/S and late-S phases were evaluated from their track structure using the RTC model. The calculated values show basically the same trend as the measured ones, which may suggest the feasibility of the new concept of clustering clusters in biophysical models.

The factors that affect the structures and stability of the adducts of cisamminedichloro(2-methylpyridine)platinum(II) with a duplex DNA were probed into by the mixed quantum chemistry and molecular mechanics (QM/MM), molecular dynamics (MD) and molecular mechanics (MM) methods. It shows that the coordinate bonds between Pt and N7G, the hydrogen bond between the amine and O6G, the weak interactions between drug molecule and DNA and the positive electron charge center position of the drug molecule in the adduct affect the stability and the steric selection of the adduct greatly. And in return the structure of the adduct determine the comparatively strengths of the coordinate bonds in the adduct.