International Journal of Nanoscience

Current information technologies totally rely on semiconductor devices and magnetic/optical discs, however, they are all foreseen to face fundamental limitations within a decade. Therefore, superseding devices are required for the next paradigm of high performance information technologies. This paper describes prospects for a molecular supercomputer which would be the only possible candidate beyond the silicon limitations. Possible four milestones for realizing the Peta/Exa-floating operations per second (FLOPS) personal molecular supercomputer are proposed. Current status and necessary technologies of the first milestone are described, and necessary technologies for the next three milestones are also discussed.

This paper describes optical patterning of sub-lithographic wavelength features using only conventional chrome-on-glass binary photomasks without phase-shift features. The sub-100 nm patterns were obtained through manipulation of masks bias designs and partial coherence control of the lithographic radiation. The key factors in the design of experiments are the density and design of masks patterns and the partial coherence of exposure radiation system used. Based on the study, smallest resolution of 36% that of designed value can be obtained for features of 75 nm using a 200 nm designed line width. Besides indication of proposed process' resolution limits for further applications, advantages of the method allows its application to applications requiring sub-100 nm critical dimensions through use of biased pattern designs, especially feasible in devices such as deep sub-micrometer comb drives actuators in nano-microelectromechanical structures; metal–semiconductor–metal photodetectors, and nanophotonic crystal structures, etc.

Dispersed aligned single-wall carbon nanotube (SWCNT) array has been formed between electrodes by electric field assisted alignment of surface decorated SWCNTs. The surface decoration of SWCNTs with functional molecules allows them to dispersedly bridge metal electrodes and effectively obviates the entanglement between SWCNTs. The influences of solution volatility and electric-field type on the alignment are investigated. It is indicated that the well-oriented SWCNT array can be achieved by using the high-volatility solvent and the high-frequency AC electric field to align SWCNTs.

A method of impedance frequency response analysis (FRA) with template multilayer organic capacitor was studied to evaluate printable materials for all-printed organic field-effect transistors (OFETs). The new method allows us not only to characterize simultaneously dielectric and conductive behaviors of the materials but also to distinguish contributions to electrical conduction or to polarization from different sources such as dielectric layer, semiconductor layer, and different interfaces for OFETs. As a dielectric layer for OFETs, Urathan is preferred because of lower conductivity, nonmetallic conduction behavior at high temperature, and lower interfacial resistance. Conductivity and dielectric enhancement of Urathan can be realized by heating. The critical temperature for conductivity and dielectricity transition was calculated from FRA from temperature dependent experiments. The method could be a standard for fast screening and assessing printable materials for OFETs.

Single wall carbon nanotubes suspended in isopropyl alcohol are placed between two Au electrodes by ac dielectrophoresis method. Total resistance including the contact resistance and intrinsic tube resistance is found to decrease from 10⁵–10⁶ Ω for as-prepared samples to 10⁴ Ω after annealing at 300°C in ambient environment. Measured I–V curves and Schottky barrier heights suggest that the electric contacts are changed from Schottky to Ohmic characteristics after annealing. These results demonstrate that annealing in ambient environment is a simple and efficient way to decrease the contact resistance.

Two effective methods for dispersion and alignment of single-walled carbon nanotubes (SWCNTs) were developed. One is the floating-potential dielectrophoresis (FPD) method, which can achieve the alignment of individual SWCNTs between two electrodes with high yield (more than 30%) and high repeatability. The second is the gas blow method. Using the shear forces associated with a rapidly moving fluid, SWCNTs were positioned in a direction corresponding to the flow vector of the fluid. This technique shows great potential for scaling up the displacement of SWCNTs with controlled orientations. Various dispersion agents including ethanol, dichlorobenzene, sodium dodecyl sulfate (SDS) and DNA were investigated with these two methods. It was found that SDS was the most effective dielectric medium used for FPD dispersion and alignment of SWCNTs. The result of electric measurement for the individual SWCNTs aligned between two electrodes suggests that, using the FPD method, both metallic and semiconducting SWCNTs could be aligned between the electrodes. The individual SWCNT resistances measured range from 20 KΩ to 5 MΩ suggesting a high contact resistance between an aligned SWCNT and metal electrodes. High resolution transmission electron microscopy (TEM) and scanning electron microscopy (SEM) characterization reveal DNA molecules wrapped around the SWNCTs after the dispersion process which may affect the intrinsic properties of SWCNTs.

A new atomic force microscope (AFM) probe for local conductivity measurement is presented. This silicon nitride based probe with a V-shaped two-dimensional sliced structure tip is patterned by using conventional photolithography method. The probe is then etched to four parallel electrodes that isolated from each other, for the purpose of performing current input and electrical potential drop measurement. The newly developed four-point AFM probe not only inherits the function of AFM surface topography generating but also has the capability of characterizing the local conductivity simultaneously. The nanoresolution position control mechanism of AFM allows the probe scanning across micrometers sized area and creating high spatial resolution map of the in-plane conductivities. Experiments have shown this four-point AFM probe to be mechanically flexible and robust. The repeatable conductivity measurements on the surface of aluminum and indium tin oxide (ITO) thin films indicate this four-point AFM probe technique has potential applications for characterizing devices and materials in microscale.

The Au ultra-fine films were grown by MBE or magnetron sputtering on Al₂O₃ or MgO single crystals which were annealed at 1000°C to obtain smooth surfaces with a step-terrace structure. A one-dimensional alignment of Au particles was partially observed around the steps on Al₂O₃(0001), surfaces at about 600°C. On the other hand, Au ultra-fine films were also deposited by magnetron sputtering on MgO(100). The two processes were proceeded to obtain C₆₀ monolayers on the above Au films. Only C₆₀ molecules adsorbed on Au remained and the others were re-evaporated by annealing at 350°C. By this re-evaporation method the nanostructured C₆₀ monolayers were fabricated. In addition self-assembly monolayers of a C₆₀ derivative, C₆₀-O-C₈SH, (C₆₀-SAM) were synthesized on the Au/MgO by soaking in benzene solution of the C₆₀ derivative. The C₆₀-SAM was obtained only along the step edges. In the case of C₆₀-SAM on ultra-fine Au films/MgO several samples showed the resistivity anomalies at 150–250 K accompanying with specific deviation from metallic linear dependences on temperature.

Carbon nanomaterials have been of great interest in nanoscience and nanotechnology because of their very small size with unique properties and simplicity in structure having only one chemical element. In our laboratory, attempts were made to synthesize carbon nanomaterials through different routes such a CCVD and pyrolysis of solids carbonaceous precursors. Pyrolysis of polyacrylonitrile fibers in presence of a suitable catalyst resulted in formation of straight as well as coil type long carbon nanofibers and tubes along with general-purpose carbon fibers. Similarly, growth of carbon nanotubes was also observed in the coke deposits during pyrolysis of pitches. The yield of CNTs formed was found to increase if the precursors are impregnated with a suitable catalyst solution. These carbon nanostructures have been characterized using XRD, TEM, SEM and TGA.

It is believed that carbon nanotubes were not able to grow on silicon substrates by chemical vapor deposition from a mixture of ferrocene and xylene. This is because iron particles (formed by the decomposition of ferrocene) reacted quickly with silicon to form a discontinuous layer (> 100 nm) of FeSi₂ and Fe₂SiO₄ particles. We report, in this letter, that by controlling the growth kinetics, aligned carbon nanotubes could be grown on pristine silicon substrates. The reason is that appropriate growth conditions could slow down and suppress the reaction within the very surface region to form an almost continuous thin layer (< 10 nm) of Fe₂SiO₄ particles; thus preventing further reaction and leaving a number of iron particles still active to catalyze the growth of carbon nanotubes. The structure and field emission properties of the nanotubes were also investigated.

Unique features and benefits of the plasma-aided nanofabrication are considered by using the "plasma-building block" approach, which is based on plasma diagnostics and nanofilm characterization, cross-referenced by numerical simulation of generation and dynamics of building blocks in the gas phase, their interaction with nanostructured surfaces, and ab initio simulation of chemical structure of relevant nanoassemblies. The examples include carbon nanotip microemitter structures, semiconductor quantum dots and nanowires synthesized in the integrated plasma-aided nanofabrication facility.

We present CMOS compatible fabrication technique for silicon nanowire (SiNW) on bulk silicon wafers. Our method uses saw-tooth etch-profiles of fins followed by self-limiting oxidation to form vertically self-aligned horizontal SiNW down to 5 nm diameter. The concept of modifying the cross-section shape of SiNW from triangular to circular and the ability to achieve desired nanowire diameter are unique in this work. Nanowires formed by such technique can be utilized to realize several nanoelectronics devices like gate-all-around transistor, single-electron-transistor, etc.; NEMS and bio-medical sensors; all in a CMOS friendly manner. The physical and electrical characterization of the SiNW is also presented in this paper.

Porous anodic alumina formation on silicon substrate is an example of a nanostructured porous array that is well-suited as a template for growing metallic nanowires. Commercial silicon wafer deposited with aluminum is used as substrate. Prior to anodization, the aluminum film is cleaned with mixture of acids solution to remove its native oxide growth. Anodization of aluminum film on silicon wafer is performed in oxalic acid solution to generate uniform and self-organized nanoporous alumina film. The pores are in the range of 60 nm diameter and pore density is about 9 × 10⁹/cm². The nanoporous alumina template is filled with nickel nanowires by wet electrodeposition process. After nanowire is grown on silicon wafer, the alumina template is etched and the as grown nickel nanowire forest is patterned using laser pruning method. The crystallinity pattern of the as grown nickel naowire forest is characterized using X-ray diffraction technique.

Here we report synthesis and investigation of Fe/ZSM-5 magnetic nanocomposites. Intercalation of iron was performed by ion-exchange procedure and by impregnation of ZSM-5 zeolite in H⁺ form by Fe(CO)₅. Magnetic nanocomposites were prepared by thermal treatment of impregnated samples in hydrogen flow at different temperatures. Chemical composition, structure and physical properties of the samples were characterized by chemical analysis, TGA, XRD, TEM, Mössbauer spectroscopy and SQUID magnetization measurements. Nanocomposites prepared by reduction of cation-exchanged zeolite indicate paramagnetic behavior even at 4 K. Repeatable ion-exchange/reduction procedure used to enrich ZSM-5 matrix with iron led to formation of bulk iron. Fe/ZSM-5 nanocomposites prepared by thermal decomposition of Fe(CO)₅ in the channels of ZSM matrix reveal their ferromagnetic behavior even at room temperature. The coercivity at 300 K for annealed samples attain 670 Oe for the crystallization temperature of 450°C. According XRD, TEM and Mössbauer data iron nanoparticles were formed in the cavities of zeolite.

The means of reducing nanoparticle contamination in the synthesis of carbon nanostructures in reactive Ar + H₂ + CH₄ plasmas are studied. It is shown that by combining the electrostatic filtering and thermophoretic manipulation of nanoparticles, one can significantly improve the quality of carbon nanopatterns. By increasing the substrate heating power, one can increase the size of deposited nanoparticles and eventually achieve nanoparticle-free nanoassemblies. This approach is generic and is applicable to other reactive plasma-aided nanofabrication processes.

Rutile structured nanocrystalline tin oxide (nano-SnO₂) was prepared by chemical precipitation method with different grain sizes. Its electrical and dielectric properties were studied using complex impedance spectroscopy under different hydrostatic pressures. These studies showed a transition in nano-SnO₂ under high-pressure. The transition pressures obtained from both the resistivity and dielectric measurements agree with each other and increase considerably with decrease in grain size. In order to find whether the transition under pressure is structural related or not, in situ high pressure Raman spectroscopy was done up to 3.38 GPa at room temperature. No structural change was observed and the transition may be due to the co-operative phenomenon of the change in band gap and better connectivity between grain boundaries.

Large-scale single crystalline In₂O₃ nanowires were successfully synthesized on anodic alumina membranes by a simple thermal evaporation method at 570°C. X-ray diffraction, transmission electron microscopy, and scanning electron microscopy studies revealed the formation of single crystalline In₂O₃ nanowires with diameters of 50–100 nm and lengths of up to a few hundreds of micrometers. Cathodeluminescence study revealed existence of oxygen vacancies evidenced by a strong and broad emission at 470 nm with a shoulder at 400 nm. The growth mechanism of the nanostructures is also discussed.

Ultrafine Sm-Lu mixed oxide powder with an overall composition Sm_1.0Lu_1.0O₃ was processed by inductive radio frequency plasma treatment using two different approaches: spraying a mixture of pure Sm₂O₃ and Lu₂O₃ with and without sintering pretreatment. Due to the insufficient reaction time and contact, the mixture sprayed without sintering shows only a marginal reaction between the two materials. Therefore, an alternative approach was adopted. The mixed oxide was first synthesized by solid state reaction at 1600°C. Then, the as-sintered pellets were crushed and ground, followed by plasma treatment. In this way, ultrafine particles of Sm_1.0Lu_1.0O₃ mixed oxide were obtained.

We report the photoluminescence (PL) from an (Er, Ge) co-doped SiO₂ film deposited by rf-magnetron sputtering in an Ar + O₂ ambience. The sample film was annealed in N₂ for 30 min at different temperatures. The PL intensity increases as the annealing temperature increases from 700 to 1000°C, and drops to very weak after 1100°C annealing. High-resolution transmission electron microscopy (TEM) observation shows that there are some Ge-rich nanoparticles precipitated after 700°C annealing, and more clusters precipitated after 1000°C annealing. However, no Ge nanocrystals were found in these films, the diffraction patterns are always halo which indicates that the precipitated clusters are in amorphous states. X-ray photoelectron spectroscopy (XPS) analysis indicates the Ge in the nanoclusters is mostly in an oxidized state and the oxidation state of Er increases with increasing annealing temperature.

Mesoporous materials were synthesized through ionic supramolecular templating for the first time by the scientists at Mobil Oil Research and Development in 1992. However more and more efforts were put into the neutral templating route in recent years due to the limitation of ionic route. In this study, mesoporous hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂ or HA) was synthesized using nonionic block copolymer pluronic F127 (EO₉₉PO₆₅EO₉₉) as template. Two groups of HA samples were prepared by coprecipitation method with different concentrations of the surfactant, which were characterized by means of X-ray diffraction (XRD), small angle XRD, electron microscopes and BJH gas absorption method. It was found that the as-synthesized and calcined samples of the two groups had a typical HA crystal phase, but the particle morphologies and pore size distribution were significantly different, depending on the surfactant concentration used. When a high surfactant concentration (10 g F127/100 g distilled water) was used, the sample obtained consisted of spherical particles (~100 nm in diameter), with a maximum distribution of pore size 58 Å. However, when the F127 concentration was 3 g/100 g distilled water, the sample with rod-like particles (~100–300 nm in length and ~40–50 nm in diameter) could be obtained, and a bimodal pore size distribution at 25.3 Å and 30 Å were also observed in this sample.

Co/Cu multilayers were electrodeposited in potentiostatic mode, using two different sulphate baths, one without any additive and other containing trisodium citrate. Deposition parameters, like deposition potential and deposition time, were established for both the baths by carrying out a series of cyclic voltammetry and chronoamperometric experiments. Thin films, having 2–20 bilayers, were electrodeposited under the established parameters. It was observed that films deposited from bath containing trisodium citrate were comparatively much smoother than films deposited from additive free bath. The films with 20 bilayers, deposited from additive free bath, exhibited a room temperature magnetoresistance of 1.5% at 9 kG, whereas magnetoresistance value enhanced to up to 5.6% at 9 kG for films deposited from trisodium citrate bath for same number of bilayers.

(La, Sr)MnO₃ (LSMO) single-layer and LSMO/YBCO double-layer films have been grown on LAO and MgO substrates using ion beam sputtering. For LSMO single-layer films, the highly epitaxial films can be grown at lower substrate temperatures down to 500°C. The epitaxy of the films, which is degraded with increasing T_S, can be restored by supply of plasma oxygen. Smaller lattice mismatch of LSMO on LAO gives two-dimensional step-and-terrace type growth, whereas on MgO grain type growth is observed due to larger mismatch. For the double-layer films, LSMO layer can be grown epitaxially on a-oriented YBCO underlayer, but a part of the underlying a-YBCO is changed into c-YBCO during the deposition of overlayer. For c-YBCO underlayer, a part of the underlying c-YBCO is changed into (110)-oriented phase after the deposition of overlayer. Then it is necessary to deposit the overlayer at lower temperatures.

Remanence enhancement has been calculated for a range of configurations, including 1D (one-dimensional), 2D and 3D arrays of hard magnetic grains, composites of hard and soft magnetic grains and triple-films. A linear relationship between the remanence M_r and the reduced domain wall width W/L has been derived analytically, which is consistent with available experimental and numerical data. For composite materials with a soft phase inserted among hard phases, the soft grain behaves like a massive inter-grain domain-wall and results in more effective remanence enhancement. In view of this, a unified formula is reached which can be applied to both composite and single phased magnets with in-plane random easy axis distribution.

In this work, the effects of flux angle, substrate temperature and deposition rate on obliquely deposited germanium (Ge) films have been investigated. We observed that the porosity of the film increased as the flux angle became more oblique. It was also possible to obtain polycrystalline Ge films at a substrate temperature of 200°C when deposition was performed using an oblique angle of 87° as compared to normal incident deposition. Raman spectroscopy results indicated that a higher substrate temperature during deposition led to an increase in crystallinity of the film. Agglomeration of the Ge film was reduced at a lower deposition rate and it was possible to obtain isolated polycrystalline Ge nanowires when the deposition was carried out with the vapor flux inclined at 87° to the substrate normal for substrate temperatures between 250°C to 300°C and with a deposition rate of 0.2–1.5 Å/s. Subsequent rapid thermal annealing of such nanowires resulted in the formation of facetted crystallites.

A nanopore array with diameter of ~30 nm was fabricated by use of focused ion beam (FIB) scanning and thin film coating on Si(100). A thin film of SiO₂ with thickness of 200 nm (used as a sacrificial layer) was coated by physical evaporation deposition (PVD) first. Next, the thin films of poly-silicon with thickness of 50 nm were coated on double side of the substrate. A window with an area of 2 × 2 mm² was opened by reactive ion etching from bottom side and reached to the thin film of SiO₂. After that, a fine controlled FIB milling with bitmap function (milling according to a designed pattern in a defined area) was used to scan the area. Signal is obtained by a sensor inside the vacuum chamber collecting secondary electrons emitted from the sputtered material when the beam reach the layer of SiO₂. Stopping the milling process at this moment, the nanopore array was derived after removing the sacrificial layer by wet chemical etching. The nanopore arrays were characterized using transmission electron microscopy (TEM) after the FIB drilling.

A molecular diode based on a conjugated co-oligomer composed of p-type and n-type segments is investigated using the first principles method. The co-oligomer is connected to Au electrodes to form an Au–oligomer–Au system. The infinite system is dealt with a finite structure confined in a device region and effects from semi-infinite electrodes. Density functional theory and nonequilibrium Green's function are used to describe the device region self-consistently. The current–voltage (I–V) characteristics of the constructed system are calculated and a rectification behavior is observed. The energy gap and the spatial orientation of molecular orbitals, and the transmission functions are calculated to analyze the I–V characteristics of the molecular diode.

In this work, the novel characteristics of a FinFET with dual-material gate (DMG) are explored theoretically using a 3D numerical simulator and compared with those of a single material gate (SMG) FinFET in terms of threshold voltage roll off, drain induced barrier lowering (DIBL) and the ratio of transconductance (g_m) to drain conductance (g_d). Our studies show that the DMG structure achieves simultaneous suppression of short channel effects (SCEs), enhancement in carrier transport efficiency and transconductance. Also, these features can be controlled by engineering the work function and length of gate material.

Since no physical approach can be employed to study the mechanism in micro cutting, the molecular dynamics simulation is becoming more and more important. In this study, the results of molecular dynamics modeling and analysis on the nanometric machining on silicon surface are presented. According to the simulation, some phenomena in the nanometric cutting process are found. First, surface elastic rebound happens on the cut surface after cutter moving away. The value of the surface elastic rebound is calculated in the simulation. Second, the atoms near the corner of work piece swirl up following the cutter moving direction at the initial stage of removing atoms from the work piece. Third, the simulation results show that no matter how small material removal is, the burr is always formed at the edge of work piece.

Very significant hysteresis characteristics are found in single wall carbon nanotubes field-effect transistors (CNTFET) fabricated using AC dielectrophoresis method. The CNTFETs show ambipolar characteristics. Two clear hysteresis loops are observed when the gate voltage is forward and backward swept. The hysteresis characteristics are studied from room temperature down to 16 K. It is found that the hysteresis loops become smaller as temperature is decreased. We suggested that the hysteresis is caused by charge trapping in foreign species covering the single wall carbon nanotube. It is more difficult for charges to transfer into and out of the trapping center at a lower temperature; as a result, the hysteresis loops become much smaller at low temperature.

We report on the process parameters of nanoimprint lithography for the fabrication of two-dimensional (2D) photonic crystals. The nickel mold with 2D photonic crystal patterns covering an area up to 20 mm² is produced by electron-beam lithography and electroplating. Periodic pillars as high as 200 nm to 250 nm are produced on the mold with the diameters ranging from 180 nm to 500 nm. Optimization of process parameters is essential to generate high-quality nanoscale patterns and control the residual stress in the mold. The mold is employed for nanoimprinting on the poly-methyl-methacrylate (PMMA) layer spin-coated on the silicon substrate. Periodic air holes are formed in PMMA above its glass-transition temperature and the patterns on the mold are well transferred. This process can be utilized for commercial applications of photonic crystal devices.

Silicon (Si) nanocrystals have been considered a good candidate for flash memory device and nanophotonic applications. The fabrication of nanocrystal memory is to form uniform, small size and high density quantum dots. In this study, nanometer-scale silicon quantum dots have been fabricated on ultrathin silicon oxide layer using amorphous silicon (a-Si) deposition followed by various annealing treatments. The a-Si layers were crystallized using furnace annealing, laser annealing and rapid thermal annealing (RTA). After annealing to form nanometer-sized crystallites, silicon wet etch was carried out to isolate the nanocrystals. The size, uniformity and density of the nanocrystals were successfully controlled by different annealing treatments. The mean dot height and mean dot diameter is 1–5 nm and 2–5 nm, respectively. Lateral growth of the silicon dots was further controlled by systemic variations of the annealing conditions. It is found that the annealed a-Si films exhibit room temperature visible photoluminescence (PL) resulting from the formation of nanometer-sized crystallites. Selective wet etch and Secco-etch treatment increased the PL efficiency that is useful for nanophotonics applications. The feasibility of quantum dot formation using ultra thin amorphous Si films is demonstrated in this work.

Glucose, carbamide and petroleum coke as carbon sources are separately added to butyl titanate and ethanol system. The initial powder containing titanium source and carbon source is prepared by sol–gel method. IR analysis of the initial powder shows that: glucose-butyl titanate system and carbamide-butyl titanate system form water-soluble compounds. After being dried, they form Ti₂O₃ and C mixed powder. Petroleum coke-butyl titanate system forms TiO₂ powder with nanometer size in carbon. Regarding initial powder as a raw material, titanium nitride powder is prepared by carbon thermal reduction. The XRD analysis shows that the titanium nitride powder is formed after the initial powder prepared in petroleum coke-butyl titanate system is kept at 1350°C for 5 h. The added Fe₂O₃ accelerates the synthesis of titanium nitride; the initial powder prepared in glucose-butyl titanate is kept at 1400°C for 5 h and then synthesizes the titanium nitride powder. Fe₂O₃ does not accelerate the synthesis of titanium nitride. The initial powder prepared in carbamide-butyl titanate system is found to form volatile material in N₂, but no titanium nitride powder is found.

A technique was investigated for the fabrication of triode-type carbon nanotube (CNT) field emitter arrays, where an integrated extraction gate was built between the nanotube cathode and the anode. The gate improves the control capability of emission currents. To fabricate the metal-gated CNT field emitter arrays, well ordered cells were generated by focused ion beam (FIB) milling of platinum (Pt) coated silicon (Si) substrate and then modified by chemical etching. Two types of catalyst elements iron (Fe) and nickel (Ni), were used for growing the CNTs inside the cells. The methods for depositing catalysts into the cells include spin coating sol–gel Fe, FIB induced decomposition of ferrocene and sputter coating pure Ni. CNT growth was carried out by a chemical vapor deposition (CVD) process. The results suggest that the CNTs grew from inside the cells where the catalysts were located. In comparison, the CNTs synthesized from the sol–gel Fe catalyst were straighter than those from ferrocene Fe and pure Ni. The density and orientation of the CNTs in each cell are directly related to the type and quantity of the catalysts and are also affected by the size of the cells.

Nanocrystalline PbF₂ was prepared by inert gas condensation technique. Structural studies using X-ray diffraction showed that as-prepared and annealed samples contained both orthorhombic and cubic phases of PbF₂. The annealed samples contain dominantly the cubic phase. For the first time Raman scattering and PL experiments were carried out on these nano-PbF₂. In addition to regular lattice vibrational modes such as T_2g for cubic phase and A_g and B_1g for orthorhombic phases, a few new Raman modes have been observed at high frequencies. PL studies confirmed that the new Raman modes are due to the presence of electronic centers. The regular modes agree well with the theoretically calculated values and previously reported experimental values.

A newly designed fullerodendron was synthesized in good yield (84%) by the use of a Diels-Alder reaction of C₆₀ with an anthryl dendron. Interestingly, the fullerodendron acts as a new catalyst that uses oxygen and light to generate singlet oxygen (¹O₂). The dendron facilitates various types of singlet oxygenation reactions including ene reaction, Diels-Alder reaction, and oxidation of phenol and sulfide.

We applied photoluminescence (PL) and photoacoustic techniques on erbium-doped porous silicon nanostructured (Er-doped-PSN) to study the influences of weight percent (%) of erbium-doped in PSN. Erbium-doped PSN has been intensively studied due their potentiality for optical devices such as waveguide and optical amplifier. Electrochemical technique was used to prepare the PSN samples. Polished p-type [100] c-Si was used as based material. Erbium doping process was carried out by electrodeposition technique using Erbium Chloride (ErCl₃) and ethanol composition as electrolyte. The weight percent of Er concentration is varied to get the optimum effect on PL. The doping process improves PL intensity and changing in peak position. Photoluminescence measurements were performed in the visible light range and excited with the 380 nm line a Xenon (Xe) light source. Photoacoustic (PA) measurements is useful to obtain the optical absorption characteristic for strongly scattering media such as PSN and it helps to confirm the possibility of a strong quantum confinement effect.

Alloy thin films of ternary system Co–Ni–Fe and binary systems Co–Fe, Co–Ni and Ni–Fe consisting of ~50 nm grains have been deposited by a simple and industrially viable technique of electrodeposition in galvanostatic mode on ITO-coated glass. Bath composition and current density have been varied to prepare films of different compositions and thus, in turn, obtain suitable composition for better magnetic properties. Further, an attempt has been made to deposit films in the presence of Mg²⁺ in the bath and to study its linkage with the magnetic properties, i.e., saturation magnetic flux density, B_S, and coercivity, H_C. Our results clearly demonstrate that addition of Mg²⁺ ions in the bath helps in increasing the B_S considerably.

Ultra fine-grained ceramic components, which can be obtained by sintering nanosized ceramic powder, provide excellent mechanical properties for engineering applications. To facilitate the cost efficient fabrication of such components, a full understanding on the sintering of nanosized ceramic materials is most helpful. In this paper, a constitutive model with density and grain size as coupling state variables was developed to study the pressureless sintering of 3Y-TZP nanosized powder. The sintering mechanism and several essential sintering parameters predicted by the model are consistent with our experimental observation. It was found that interface reaction mechanism is dominant during the densification process, and the model was also proved to provide reliable prediction on densification and grain growth.

The distribution of flux of carbon-bearing cations over nanopatterned surfaces with conductive nanotips and nonconductive nanoislands is simulated using the Monte-Carlo technique. It is shown that the ion current is focused to nanotip surfaces when the negative substrate bias is low and only slightly perturbed at higher substrate biases. In the low-bias case, the mean horizontal ion displacement caused by the nanotip electric field exceeds 10 nm. However, at higher substrate biases, this value reduces down to 2 nm. In the nonconductive nanopattern case, the ion current distribution is highly nonuniform, with distinctive zones of depleted current density around the nanoislands. The simulation results suggest the efficient means to control ion fluxes in plasma-aided nanofabrication of ordered nanopatterns, such as nanotip microemitter structures and quantum dot or nanoparticle arrays.

A simplified micromagnetic model has been proposed to calculate the hysteresis loops of nanostructured permanent magnets for various configurations, including thin films, exchange-coupled double-layer systems and bulk materials. The reversal part of the hysteresis is based on the Stoner–Wohlfarth coherent rotational model and the coercivity mechanism is due mainly to the motion of the transition region (a domain wall like magnetic moment distribution in the grain boundary). The elements of nucleation and pinning models are also incorporated.

Nanoscale machining involves changes in only a few atomic layers at the surface. Molecular dynamics (MD) simulation can play a significant role in addressing a number of machining problems at the atomic scale. In this paper, we employed MD simulations to study the nanometric cutting process of single crystal copper. Instead of the widely used Morse potential, we used the Embedded Atom Method (EAM) potential for this study. The simulations were carried out for various tool geometries at different cutting speeds. Attention was paid to the cutting chip formation, the cutting surface morphology and the cutting force. The MD simulation results show that both the tool geometry and the cutting speed have great influence on the chip formation, the smoothness of machined surface and the cutting force.

Novel devices such as Double Gate (DG), Triple Gate (TG) or FinFET, Pi-Gate (PG) and Omega-Gate SOI MOSFETs are potential candidates for achieving the performance predictions of the International Roadmap of the Semiconductor Industry Association. In this paper, we analyzed the DG, TG and PG in comparison with the Single Gate (SG) SOI MOSFET using the commercial 3D numerical simulator SILVACO in the DC and AC regimes from subthreshold region to strong inversion and saturation regions. In the DC regime, multiple gate devices are superior to SG device from micrometer down to nanometer scale lengths. In the AC regime, the advantages of the multiple gate devices over SG devices are significant especially when the channel length reduces below 100 nm. For the first time, we have shown the great interest and potential of these multiple gate devices for high frequency analog applications.

Spherulite is an important crystal growth form in many organic and inorganic substances. In the sol-to-gel transition of the N-lauroyl-L-glutamic acid di-n-butylamide (GP-1)/propylene glycol (PG) system, the formation of spherulitic fiber network was observed in situ by optical microscopy. The growth mechanism of the spherulite in the gelation process was examined quantitatively. A constant growth rate along the radial direction of the spherulite was ascribed to the surface kinetics controlling mechanism, in which a constant supersaturation throughout the spherulitic growth may be induced by the topological structure of the densely branching morphology in this gel network. Our results also indicate that the engineering of a fiber gel network can be attained via crystallization strategies, since spherulitic growth is a typical example that construction of supramolecular structure occurs as a consequence of the crystallization from dilute solutions.

Pure zirconium oxide nanocrystalline particles of the size range 6–140 nm in diameter are fabricated from ultrafine metallo-organic complexes by thermal hydrolysis at 120°C and heat treatment at 125 to 1025°C. X-ray powder diffraction for nearly monodispersed nanocrystallites reveals that the critical size of the ferroelastic transition between the tetragonal and monoclinic phases is around 25 nm in diameter. The critical size from the cubic to the tetragonal is strongly suggested to be 5 nm in diameter by X-ray photoelectron spectroscopy.

Titanium dioxide (TiO₂) nanoparticles in the anatase phase were coated on fly ash by using a sol–gel method. The TiO₂ nanoparticles coated on fly ash were produced from titanium tetraisopropoxide (Ti(OPrⁱ)₄ 3.3 M) in absolute ethanol, and the fly ash was added into this alcoholic solution. The ratio of TiO₂ nanoparticles to fly ash in the coating process was 1:10 by weight. The ethanolic solution was loaded into a pouch type cellophane membrane and placed for 1 h in a clear solution which containing 1:1 (v/v) ratio of absolute ethanol and distilled water with 0.5–1% concentrated (25%) ammonia solution. After the dialysis process was completed, the mixture was then allowed to dry in an oven at 100–110°C and was calcined in a furnace over the temperatures range of 400–800°C. TiO₂ nanoparticles were then analyzed and characterized by using the techniques of XRD, SEM, EDS, TEM, and BET. The crystalline sizes of anatase form were found to be in the range of 15–20 nm. The characteristics of TiO₂ nanoparticles coated on fly ash were further investigated by utilizing SEM and EDS methodologies. The correlations among crystalline phase, particle size, morphology, and specific surface area were investigated.

Potassium bismuth titanate nanoparticles were prepared by the hydrothermal method using Ti(C₄H₉O)₄ and Bi(NO₃)₃·5H₂O as raw materials in alkaline solution at temperatures of 160–200°C. The crystal phase, particle size, morphology and dispersion of the particles were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the particles with sizes of about 50–100 nm in diameter are well-dispersed K_0.5Bi_0.5TiO₃ (KBT) crystals of tetragonal structure, and the alkaline concentration and the temperature of solutions have great effects on the phase composition and morphology of the resultant particles. We could gain the KBT phase of high purity when the concentration of KOH is about 8–12 M and the reaction temperature is about 170–180°C.