International Journal of Modern Physics B

Diamond thin films were grown on diamond (100) substrates in oxygen atmospheres by pulsed laser deposition (PLD) using an ArF excimer laser. The suitable oxygen atmosphere of 5 × 10^-2 Torr can etch the sp² bonding fractions preferentially. At substrate temperatures between 550°C and 650°C, single-phase diamond films consisting of diamond crystal with diameters of 1 - 5 μm could be grown. The results demonstrated that the diamond thin films can be grown homoepitaxially using PLD by controlling the deposition parameters, such as the oxygen pressure and the substrate temperature.

We have investigated the effect of using a magnetic field to confine and focus the plasma in a Filtered Cathodic Vacuum Arc (FCVA) deposition system used for the preparation of tetrahedrally bonded amorphous carbon (ta-C) thin films. The design of the magnetic field is such that the plasma can be confined into a high-density focussed spot or de-focussed into a lower density wide beam. Increasing the magnetic field directly increases the plasma density and thus increases the deposition rate. The ta-C films grown in the magnetic field were subsequently characterised. EELS and Raman measurement were used to measure the sp3/sp2 ratio and UV-vis spectroscopy for optical bandgap studies. The intrinsic stress and I-V characteristics of the thin films were also studied. The results show that it is possible to deposit the films at rates as high as 2.5 nm/sec without adversely affecting the material properties.

Efficient hydrogenated diamond-like carbon (DLC) film deposition in a plasma reactor that features both the capacitive and inductively coupled operation regimes is reported. The hydrogenated DLC films have been prepared on silicon chemical vapor deposition (CVD) system. At low RF powers, the system operates as an asymmetric capacitively coupled plasma source, and the film deposition process is undertaken in the electrostatic (E) discharge regime. The films deposited in the electrostatic mode feature graphite-like structure. Above the mode transition threshold, the high-density inductively coupled plasma is produced in the electromagnetic (H) discharge regime. Raman spectrometry suggests the possibility to control relative proportions of sp² and sp³ hybridized carbon. Variation of the DC substrate bias results in dramatic modification of the film structure from the polymeric (unbiased substrates) to the diamond-like (optimized bias). It has been shown that the deposition rate and hardness of the CH₄+Ar gas mixture discharge, the DLC film exhibits mecha nical hardness of 18 GPa, Young's modulus of 170 GPa, and compressive stress of 1.3 GPa.

We have grown laterally overgrown diamond films on stripe patterned silicon substrates by microwave plasma chemical vapor deposition. Titanium was used as the mask material and stripe patterns were fabricated using conventional photolithographic method. The selective growth area and the metal mask part order to enhance the crystal nucleation was performed before photolithographic process. SEM observation revealed that the diamond film was laterally overgrown on titanium mask. The result width of diamond film was 16 μm. The grain size on mask region was about three times as large as that g rown on nucleation region.

Hard and smooth nanocrystalline diamond (NCD) thin films were deposited on polished silicon substrates by biased enhanced growth in microwave plasma chemical vapor deposition. The films deposited with varying the methane concentration and biasing voltage were characterized by Raman spectroscopy, nano-indenter, x-ray diffraction and atomic force microscopy. Stress in the films increases with decreasing methane concentration in the gas-phase and with increasing biasing. The adhesion between NCD film and Si substrate is very strong sustaining the compressive stress as high as high as 85 GPa. It was hypothesized that hydrogen content of the films and graphitic content of the films are responsible in generating stress. The hardness is well correlated with the Raman peak intensity ratio of NCD peak to G peak.

We have synthesized well-aligned, uniform carbon nanotubes (CNTs) in large area at low temperature of 500°C using microwave plasma- enhanced chemical vapor deposition on silicon and Corning glass 7059. This is a two-step process in that ion beam sputtering deposition was used to deposit iron catalyst thin films and followed by hydrogen plasma pretreatment to form nano-size Fe particles before the CNTs growth at the second step. The thickness of Fe catalyst thin film was found to be the most important factor in the low temperature CNTs growth process. Systematic control of the length, diameter, and alignment of the CNTs has been achieved by changing the deposition parameters such us microwave power, pressure, temperature and the thickness of Fe catalyst. High resolution SEM and TEM were used to characterize the morphology and structure of the nanotubes. Field emission measurement showed a low turn on field (6.2 V/m) and high emission current density (0.1 mA/cm² at 9 V/m) for the films grown at low temperature of 500°C.

We report on the growth of hydrogenated amorphous carbon (a-C:H) films, using a simple dc glow discharge plasma chemical vapor deposition method. A variety of complementary techniques were employed to analyze the properties of these films. a-C:H films having high fraction of tetrahedrally (sp³) bonded carbon atoms (~ 70%) and low hydrogen content (< 5at.%) were obtained. These films were characterized by a high optical bandgap ~ 2.7 eV, and refractive index (at 600nm) ~ 2.2. Growth of metastable diamond structure in a-C:H is attributed to energetic condensation of carbon containing ions in (sp³) configuration.

gas ambient with varying substrate temperature from 20°C to 500°C. The effects of the substrate temperature and ambient nitrogen gas pressure on the surface morphology, composition, structure, and electrical properties of the nitrogen incorporated camphoric carbon thin films have been investigated by standard techniques. We found that the amorphous structure of CN_x films can be changed by substrate temperature and the CN_x films with high nitrogen content have relatively high electrical resistivity.

We have studied the effects of ambient Helium gas pressure on the optical, structural and physical properties of the diamond like carbon thin films using a camphoric carbon (CC) soot target, deposited by pulsed laser ablation. Both the optical gap and electrical resistivity are found to increase with 2.6 Torr leads to a decre ase in optical gap and electrical resistivity. The films are further investigated by different spectroscopic techniques such as, Raman, XPS and FTIR spectroscopy, and surface morphological techniques like SEM and AFM. Improvement of the opto-electrical and structural properties of the diamondlike carbonaceous films deposited in helium environment using CC soot target reveal different behaviour than reported earlier.

In this paper, we studied the effects of hydrogen gas flow ratio of [H₂]/[N₂ + CH₄ + H₂] on the quality of nanometer diamond (nano-diamond) films prepared by microwave plasma enhanced chemical vapor deposition method. Nano-diamond films were deposited on the silicon substrates from a gaseous mixture of nitrogen, methane and hydrogen. The experimental results show that if only using a gaseous mixture of nitrogen and methane, although we can obtain nano-diamond films with a grain size of about 5nm, the diamond films contain much non-diamond components. With hydrogen addition, and with increasing the hydrogen gas flow ratio from 1 to 10%, the non-diamond components in the films are significantly reduced and the grain size of the films increases from 5nm to 60nm. However optical transmittance of the films increases with increasing hydrogen gas flow ratio from 1 to 7% because of an improvement of film quality, and then decreases with further increasing hydrogen gas flow ratio owing to the increase of film roughness.

Diamond films were grown on steel substrates by a hot filament chemical vapor deposition method without any special substrate pretreatment. When the deposition time was extended from 15 to 83 hrs and above, non-graphitic interfacial layers were formed below diamond films. The interfacial layers were solid and mediated good adherence of diamond films on steel substrates. The interfacial layers were found to be iron and chromium carbides with traces of oxygen as determined by chemical analysis using a scanning Auger microscopy (SAM). The carbide interfacial layers probably resulted from graphitic conversion processes. It is assumed that the graphitic conversion was established on chemical reaction pathways driven by thermal diffusion processes between the earlier formed graphitic layers and atomic constituents of the steel substrates.

A computer model have been set up for simulation of the flow and temperature field, and the radial distribution of atomic hydrogen and active carbonaceous species over a large area substrate surface for a new type dc arc plasma torch with rotating arc roots and operating at gas recycling mode A gas recycling radio of 90% was assumed. In numerical calculation of plasma chemistry, the Thermal-Calc program and a powerful thermodynamic database were employed. Numerical calculations to the computer model were performed using boundary conditions close to the experimental setup for large area diamond films deposition. The results showed that the flow and temperature field over substrate surface of Φ60-100mm were smooth and uniform. Calculations were also made with plasma of the same geometry but no arc roots rotation. It was clearly demonstrated that the design of rotating arc roots was advantageous for high quality uniform deposition of large area diamond films. Theoretical predictions on growth rate and film quality as well as their radial uniformity, and the influence of process parameters on large area diamond deposition were discussed in detail based on the spatial distribution of atomic hydrogen and the carbonaceous species in the plasma over the substrate surface obtained from thermodynamic calculations of plasma chemistry, and were compared with experimental observations.

The interest in diamond windows for the application of high power radiation technology is increasing continuously due to its outstanding thermal and opto-electronic properties. In order to analyze the surface properties of very highly polished polycrystalline diamond in the sub-micrometer down to nanometer regime, two different near-field microscopy techniques have been employed.

By using a Scanning Thermal Microscope (SThM) it is possible to uncover the varying thermal conductivity of different diamond grains. Dissimilar thermal surface properties within diamond grains have been measured with a resolution in the nm regime. Beside the fact of determining a small surface thermal conductivity compared to the well known data of bulk material, the thermal conductivity of inferior and superior diamond quality is separated quantitatively. Additionally the opto-electronic properties of the polished diamond have been investigated by Scanning Near-Field Cathodoluminescence (NF-CL). This measurement technique allows the detection of the distribution of dislocations within diamond grains with a resolution of less than 100nm. The comparison of these results, obtained by SThM and NF-CL, demonstrates a fine alignment in representing crystal lattice imperfections.

Investigation of visible light excited photoluminescence (PL) in HPHT synthetic diamonds, grown in the Ni-containing melt, revealed a variety of new systems. The PL excitation spectra were recorded for the most intense systems and position of zero-phonon lines and energies of participating phonons were determined. Analysis of PL versus annealing temperature T and ESR data allowed one to establish a sequence of nickel defect transformations as T increases. Only PL systems related to complicated nickel-nitrogen complexes with number of nitrogen atoms n ≥ 2 were found in natural diamonds.

Diamond fibre reinforced poly (methylmethacrylate) (PMMA, perspex) composite blocks (100 × 10 × 4 mm) have been fabricated by embedding CVD diamond coated tungsten wires within a perspex matrix. Various volume fractions of diamond have been used, as well as varying positions of the fibres within the composite. We find that even 1% fibre volume fraction can lead to an increase in the Young's modulus of the composite of a factor of 6.

It is studied the absorption edge and photoluminescence (4.2-900 K) in the a-C:H films on silica substrates prepared by the decomposition of 10%CH₄+90%Ar gas mixture in the RF plasma under various growth conditions E/p (E – electric field strength, p – gas mixture pressure). With E/p increase, the optical band gap width and Tauc slope decrease, photoluminescence intensity and photoluminescence excitation spectra shift to a lower energy region while halfwidth of the photoluminescence intensity spectra broadens. It is firstly fabricated the multilayer low-size a-C:H/a-Si:H structures where a-C:H layer with E_g = 4.5 eV is used as a barrier. Quantum size effects are found in a-Si:H with the thickness lower than 100 Å. Photoluminescence studies of a-Si:H show the presence of a sharp interface region in the a-C:H/a-Si:H structures where the charge carriers exist in the state of quantization.

In this paper, based on the Fuchs and Sondheimer theory and valence band split-off model, a theoretical description of the piezoresistive effect in P-type heteroepitaxial diamond films was presented by solving the Boltzmann transport equation in the relaxation time approximation, in which a mixed scattering by lattice vibration, ionized impurities and surface was considered. A calculating expression of the piezoresistive effect has been developed in a parallel connection resistance model for the light-hole band, the heavy-hole band and the split-off band. The calculating results were in good agreement with the experimental data, indicating that the prezoresistive effect in diamond films was mainly ascribed to the hole band split-off under a uniaxial stress.

Diamond materials have become progressively significant in the fabrication of heat sinks for power devices and lasers. To investigate the influence of polishing on CVD-Diamond, the surfaces of <100> and <110> coatings were analyzed, after a first abrasive treatment on a 30μm diamond grit by scanning thermal microscopy based on a resistive platinum-probe. This technique describes in first order approximation the heat transfer of a metal-diamond interface. Through this method it was possible to diagnose a relevant reduction in thermal conductivity by a harsh sample preparation depending on the crystal orientation. The thermal conductivity of as deposited <100> diamond was measured at 1290 W/mK and was reduced to 250 W/mK. The thermal conductivity of as deposited <110> diamond was determined at 1780 W/mK whereas the same diamond surface, but abraded, shows a thermal conductivity of just 460 W/mK. Additionally the received images which represents the thermal conductivity qualitatively bring forward micro structures like e.g. grain boundaries.

Low resistance ohmic contacts were fabricated on diamond films. A high boron concentration (~10²⁰cm^-3) was obtained on the surface by ion implantation. The initial film of Ti (20nm) followed by Au (100nm) was deposited by r. f. sputtering. I-V measurements showed that the as-deposited contacts were ohmic. Upon annealing, the ohmic characteristics of the contacts were improved significantly. The specific contacts resistivity decreased from 6.2 × 10^-3 to 1.2 × 10^-6Ωcm² as a result of post-deposition annealing. The X-ray photoelectron spectroscopy analysis indicated the formation of titanium carbide at the Ti/diamond interface in the as-deposited and annealed states. A low oxygen concentration was observed.

Nanocomposite amorphous carbon (a-C:Me) films including a-C:Ni, a-C:Co, a-C:Ti, a-C:W, a-C:Fe, a-C:Al, and a-C:Si films were deposited using metal-carbon composite target by filtered cathodic vacuum arc (FCVA) technique. Atomic force microscopy (AFM), Raman, and X-ray photoelectron spectroscopy (XPS) were used to characterize the morphology and structure of the films. Nanoindenter and surface profilometer were used to determine the hardness, Young's modulus, and internal stress. Contact angle and field emission experiments were used to study the surface energy and field emission properties of the films respectively. The influence of the type of elements and its composition in the target on the structural, mechanical, surface energy, and field emission properties were studied. The incorporation of elements into the films results in the decrease of sp³ C fraction, internal stress in the deposited films, but the hardness and Young's modulus remains at high level. The effect of non-carbide forming elements in the films on the mechanical properties is more pronounced than that of carbide forming elements. The surface energy of the films increases with incorporating Ni atoms, but decreases after incorporating Fe and Al atoms into the films. After heat treatment, the incorporation of metal into ta-C films can greatly improve the field emission performance.

Tetrahedral amorphous carbon (ta-C) films which contained aluminum element were fabricated by filtered cathodic vacuum arc (FCVA) method. The tribological characteristics of the ta-C films were investigated with ball-on-disk tribometer. The increment of aluminum in the ta-C film leads to an increase of sp² carbon bonding and a decrease of sp³ fraction in the film. The roughness of the films was measured with atomic force microscope, and the hardness and Young's modulus of the films were measured with nanoindentation. The results showed that the film hardness and Young's modulus dropped with the increase of Al content in the films. The results have been interpreted with respect to the change of sp³ and sp² fractions in the ta-C:Al films.

The Co-Cr-Mo alloy is extensively used for tribological applications, including orthopaedic components in total joint replacements. High quality diamond-like carbon (DLC) coatings on metal/alloy substrates are of great interest as they are able to protect them from severe wear and thus prolong the life span of the component. Since the roughness of the metal/alloy varies depending on the applications, a study has been carried out to investigate the effect of substrate surface roughness on the microstructure, sliding life, wear-resistance, coefficient of friction, adhension and hardness of DLC coatings prepared on Co-Cr-Mo alloy substrates under the same deposition condition.

The microstructure of the films studied using Raman spectroscopy suggests that the film prepared on a smoother surface contains slightly higher fraction of sp³ bonded carbon atoms. The characterization using a pin-on-disk tribometer reveals that, the film prepared on the roughest sample (Ra ~ 0.06 μm) exhibits a very short life span of about 20 cycles compared to the film that is prepared on a relatively smoother surface (Ra ~ 0.02 μm), which exhibits a life span of about 340,000 cycles. In order to investigate the origin of this improved property of the DLC film on the smoother surface, adhesive strength and hardness of the films were studied by using a micro-scratch tester and a Nano-indenter, respectively. The results suggest that the film prepared on the smoother surface exhibits better adhesion (higher critical load) and relatively higher hardness.

The adhesion, of a coating to the underlying substrate, in terms of critical load (using scratch test) is complex and is a function of many parameters such as coating thickness, interfacial stress, coefficient of friction, intermixing, hardness, structural parameters, etc. The present study examines the relationship of critical load to other properties such as film thickness, compressive stress, coefficient of friction, etc. of diamond-like carbon coatings prepared under floating condition (no substrate bias), on silicon substrates. The results show that the compressive stress increases with increasing thickness. However, the adhesive strength in terms of critical load increases with increasing the film thickness up to a certain value and then it decreases. The decrease in critical load with thickness of the films is due to the dominant effect of compressive stress.

In order to obtain the parameters that affect the adhesion, a factor analysis has been carried out on the experimental data using SPSS — a statistical software package. Thickness, stress, and critical load emerged as one of the factors and hence it suggests that thickness and stress are two primary parameters that affect adhesion. None of the parameters of Raman study were emerged in the factor analysis along with critical load and thickness. This suggests that the variation of the sp³-bonded carbon with thickness is relatively small and that may not have any direct impact on the adhesion. In this case, stress shows a strong linear relationship with thickness. Moreover, it is not an operational parameter. Hence inclusion of stress in the model becomes unnecessary. Therefore, an empirical relation has been obtained for critical load as a function of thickness.

Tetrahedral Amorphous Carbon (ta-C) thin film by using Filtered Cathodic Vacuum Arc (FCVA) technique has proven to be wear-resistive and corrosion resistant for a wide range of electrical, optical, and mechanical applications. Many investigations have shown that the ta-C film prepared by the FCVA technique can provide a superior ultra thin overcoat for the sliders and media compared to ECR-CVD and IBD coating technology. The ta-C film excels in terms of the film density, hardness, surface roughness and corrosion resistance. Nanofilm Technology International (NTI) has successfully developed and commercialized the FCVA coating system (FS series) for the slider overcoat application, which provides a good quality film with a high hardness (~50 GPa), low stress (2~3 GPa), low macro-particle density (~1/cm² for particles > 0.3 μm), good uniformity (< 4%$ in 8 inch coating area) and high production repeatability (< 5%).

With the trend of decreasing the thickness of the carbon overcoat on high-density magnetic recordings, the corrosion properties of a hard disk multilayer structure are becoming a hot issue. An ideal overcoat would be uniform across the disk's surface, have low porosity and electrical conductivity as well as being impermeable to water. However, in reality this is not viable and corrosion is inevitable. One possible method of improving the corrosion resistance of carbon overcoats is to introduce carbide bilayers. In this paper the corrosion protective properties of CrC/C and BC/C nanolaminated overcoat structures have been analyzed by an electrochemical technique based on LPR measurements. The results allowed an overcoat's resistance to be correlated to its porosity and a statistical method was developed to allow easy comparison of results. The results from the electrochemical measurements were correlated with a range of surface analysis techniques.

The deposition process of carbon coating by plasma CVD was studied for the development of a high-density magnetic disk with an ultra thin overcoat of about 4nm thickness. A hot filament discharge system was installed to disk production equipment for the simultaneous deposition of a carbon thin coating on both sides of the disk. The hot filament high-density plasma, in a low-pressure atmosphere of 0.5Pa, was found to be more advantageous, compared with other CVD sources, such as radio frequency plasma, in deposition of the hard carbon thin coating on a negatively biased substrate with ion incidence to the sample. Ion impinging on the substrate was evaluated by calculating its contribution ratio, roughly, from growth rate and bias current density, then examined in relation to the hardness of the carbon thin coatings. In conclusion, hot filament plasma, as a stable CVD source, enables the deposition of the hard carbon overcoat at over 10GPa at the rate of about 1 nm/s, by generating high-density plasma in a low-pressure atmosphere.

We have grown carbon nanotubes (CNTs) on the soda-lime glass substrates using chemical vapor deposition of C₂H₂ gas at 550°C. We used electro-plated Ni thin film as a catalyst and screen-printed Ag thick film as a cathode. The turn-on field was about 2.55 V/μm with an emission current density of 10 μA/cm², and electric field was about 4.0 V/μm with an emission current density of 3 mA/cm². Fowler-Nordheim plot shows good linear fit, indicating that the emission current of CNTs follows the Fowler-Nordheim behavior. This process is suitable for mass production of CNT field emission display(CNT-FED), because of its merits; low temperature (≤ 550°C) process, easiness of CNT patterning, non-vacuum process, large area uniformity.

We studied the field emission properties of carbon nanostructure, which comprised of high density carbon nanotips on Si. These carbon nanotips are grown on metal coated Si by a high density plasma chemical vapor deposition (HDPCVD) using an inductively coupled plasma. The emission current increases with increasing the growth temperature. They exhibited an emission current density of 1 mA/cm² at a field of 1.95 V/μm when the growth temperature was 700°C. We developed high brightness field emission lamps using the carbon nanotips.

Hydrogenated amorphous carbon films were fabricated with and without hydrogen dilution in a small d.c bias-assisted plasma chemical vapor deposition system. It was found that the hydrogen dilution can reduce the sp²/sp³ ratio in carbon films which results in blue shift of room temperature photoluminescence spectrum. The field emission characteristics were investigated by using parallel plates test configuration. A very low threshold electric field (~0.5 V/μm) was achieved from thin amorphous carbon film prepared with hydrogen dilution. The improvement to field emission property in the present carbon films was tentatively attributed to the field enhancement effect due to the electronic structure inhomogeneity of the carbon films and the reduction of the surface emission barrier due to the hydrogen termination.

In our study, diamond-like-carbon (DLC) thin films were prepared by filtered arc deposition (FAD), which provided a way to deposit DLC thin films on large areas at room temperature. Glass slides coated 100nm chromium or titanium thin films were used as cathode substrates. Millions of rectangular holes with sizes of 5 × 5μm were made on the DLC films using a routine patterning process. Here a special reactive ion beam etching method was applied to etch the DLC films. The anodes of the devices were made by electrophoretic deposition. ZnO:Zn phosphor (P15) was employed, which has a broad band bluish green (centered at 490nm). Before electrophoretic deposition, the anode substrates (ITO glass slides) had been patterned into 50 anode electrodes. In order to improve the adherence of phosphor layers, the as-deposited screens were treated in Na₂SiO₃ solution for 24h to add additional binder. A kind of matrix-addressed diode FED prototype was designed and packaged. 50-100μm-thick glass slides were used as spacers and getters were applied to maintain the vacuum after the exhaustion. The applied DC voltage was ranged in 0-3000V and much higher current density was measured in the cathode-patterned prototypes than the unpatterned ones during the test. As a result, characters could be well displayed.

Nanocrystalline diamond field emitters were deposited by microwave plasma-enhanced chemical vapor deposition using porous Si as host matrixes. Scanning electron microscopy observations showed that the nuclei of diamond occurred at the edges of the etched pores, and the nanoscale diamond grains were partly embedded into the pores of the porous Si. The structure was beneficial to the electron field emission. The electron emission became more stable and the emission current was significantly enchanced comparing with those of the diamond films deposited on Si substrates scratched by diamond powder.

This study presents the investigation of CVD diamond for the application of an UV TL dosimeter. A 9-μm-thick film used in this study presents a TL glow curve with a well-defined first-order kinetic peak (at about 273 K), which norm ally presents in the glow curve from ionizing radiations, is not observed. By fitting the glow curve to a first-order kinetic model, the trap activation energy E_t = 0.95 eV and frequency factor s = 5.6 x 10⁶s^-1 have been resolved.

Diamond-like carbon (DLC) films were deposited with a RF magnetron sputtering device. The target used was high purity graphite (99.999%) and n-type Si was used as the substrate. In order to get good anti-reflective films nitrogen gas was used to a small extent in addition to hydrogen gas thus resulting in a-C:H:N thin films. From the Ellipsometry studies it was found that the deposited films were good for optical coating. XPS studies indicate that film contains carbon in graphitic form, DLC form and CN bonding in sp² trigonal and sp³ tetrahedral structure. FT-IR spectra analysis agrees with the results of XPS data. AFM studies show that the surface roughness of the films depend on the film composition.

Nanocrystalline diamond thin films have been grown on both sides of Si wafer by microwave plasma-enhanced chemical vapor deposition using a mixture of CH₄ and H₂ as source gas. It was shown that infrared transmission of Si has been greatly enhanced and the maximum transmittance reaches 85%. By optimizing the film thickness, we can obtain the maximum increment in the desired infrared wavelength range. Sand spraying test showed that, while the bare Si substrate exhibited obvious surface damage, no damage could be observed on the diamond surface after the sand spraying. The results confirm that the nanocrystalline diamond films coated on Si can not only increase the infrared transmission but also act as a protective coating.

The CVD diamond UV photodetector shows more than four orders of photoresponsivity discrimination between UV and visible light. Post-treatment on as-fabricated photodetector is essential for a good response to UV light and blindness to visible light. The CVD diamond X-ray detector shows linear dependence of photocurrent on X-ray intensity and high response speed. The mapping of charge collection efficiency on the whole sensing area of a CVD diamond alpha particle detector has been obtained using ion-beam-induced charge microscopy technique. Three peaks have been observed in the charge collection spectrum.

Diamond-like carbon (DLC) films with different structure were deposited on highly electrically conductive silicon substrates (SiO₂/Si), using dc magnetron sputtering deposition process. Their structure and electrochemical behavior in 0.5 MH₂SO₄ solution were studied with micro-Raman spectroscopy, electrochemical impedance spectroscopic (EIS) analysis and film impedance. The double layer capacitance on the DLC films was about 0.571 - 3.91 μF-cm^-2. The capacitance increased with the increased Raman spectrum intensity ratio I_D/I_G and accelerated at around 2.25 of the ratio. The results suggest that the potential of DLC films as electrode materials for electrochemical analysis.

Ta-C and iron containing amorphous carbon (a-C:Fe) films were deposited by filtered cathodic vacuum arc technique. The influences of Fe contents on the wettability of the films were investigated in terms of surface energy. The surface energy of a-C:Fe films was determined by the contact angle measurement. Atomic force microscopy (AFM), Raman spectroscopy and X-ray induced photoelectron spectroscopy (XPS) were employed to analyze the origin of the variation of surface energy with various Fe content. It is found that the contact angle for water increases significantly after incorporating Fe into the films and the films become hydrophobic. The roughness of these films has a little effect on the contact angle. The surface energy is reduced after incorporating Fe into the a-C film which is due to the reduction of both dispersive and polar component. The reduction in dispersive component is ascribed to the decrease of atomic density of the a-C:Fe films due to the increase in sp² bonded carbon. The absorption of oxygen on the surface play an important role in the reduction of polar component for the a-C:Fe films. It is proposed that such network as (C_a-O-Fe)-O-(Fe-O-C_a) may be formed and responsible for the reduction of polar component.

In this work we report on the deposition of hydrogenated nanocrystalline silicon carbide (nc-SiC:H) films using an electron cyclotron resonance chemical vapor deposition (ECR-CVD) system with silane (SiH₄) and methane (CH₄) as source gases. It was found that the conditions of strong hydrogen dilution and high microwave power are necessary for the fabrication of nanocrystalline SiC grains, which are found to be embedded in an amorphous matrix. The films have been studied using high resolution transmission electron microscopy, infrared absorption, Raman scattering and x-ray photoelectron spectroscopy. All the results have confirmed the prescence of SiC nanocrystallites. Very strong photoluminescence (PL) could be observed from these films at room temperature, with a peak energy of 2.64 eV. This energy, being higher than the optical bandgap of 3C-SiC, can be possibly due to quantum size effect in these crystals, which are embedded in an amorphous matrix of larger bandgap. Time-resolved PL at the peak emission energy exhibits a bi-exponential decay process with lifetimes that are in the order of picoseconds and nanoseconds, which are at least 2 orders of magnitude faster than that of bound excition transitions in bulk 3C-SiC at low temperature. The strong light emission and short PL lifetimes observed strongly suggest that the radiative recombination is a result of direct optical transitions in the SiC nanocrystallites. It was found that upon ultraviolet irradiation using an Ar⁺ laser (351 nm), the PL intensity of the films was enhanced. After 20 minutes of irradiation, the PL intensity increased by about three times. This result suggests that the UV light may lead to modification of nonradiative recombination centers in the films.

Intense photoluminescence (PL) has been observed at room temperature from the polycrystalline SiC samples prepared from carbon-saturated Si melt at a temperature ranging from 1500 to 1650°C. Composition and structure of the samples have been confirmed by means of X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. PL measurements with 325 nm UV light excitation revealed that the room temperature PL spectrum of the samples consists of 3 luminescent bands, the peak energies of which are 2.38 eV, 2.77 eV and 3.06 eV, respectively. The 2.38 eV band is much stronger than the others. It is suggested that some extrinsic PL mechanisms associated with defect or interface states would be responsible to the intensive PL observed at room temperature.

We present a simple thin film encapsulation technique for organic light emitting devices (OLEDS), for use in flexible flat panel displays (FPDs). We systematically studied the moisture-resistant properties of silicon nitride thin films prepared by plasma-enhanced chemical vapor deposition (PECVD) and found that silicon nitride thin films have a low water vapor permeation (WVP) rate even deposited at low substrate temperature (20°C). Then OLEDs prototypes were successfully packaged by depositing silicon nitride thin films on them. Based on the analysis of the degradation of the OLEDs, we found the lifetime of the encapsulated devices was increased by more than two orders of magnitude over that of the unencapsulated ones. Our results demonstrated the feasibility of thin film packaging for OLEDs and the possibility to realize the flexible FPDs.

A series of hydrogenated amorphous silicon carbide (a-Si_1-xC_x:H) films (0 < x ≤ 1) were grown by using an organic source, xylene (C₈H₁₀), instead of methane (CH₄) in a conventional plasma enhanced chemical vapor deposition system. The optical band gap of these samples was altered over a wide range by changing the gas ratio of C₈H₁₀ to SiH₄, the maximum value can be reached as high as 3.6eV. Photoluminescence (PL) measurements were carried out at room temperature by using a Xe lamp as an excitation light. It was found that the PL peak is blue shifted with increasing optical band gap. The xylene-based a-SiC:H electro-luminescence (EL) device structure was also fabricated and room temperature EL behavior was investigated. It was found that the EL peak depended on the band gap of a-C:H films and a stable emission can be obtained by using the suitable structure parameters.

The effect of the Si-C, Si-CH₃, C-H_n, Si-H and Si dangling bonds on the oxidation process was investigated by monitoring the changes of these bands as a function of oxidation temperature or duration using the infrared spectroscopy technique. We concluded that the activation energy obtained from the linear regime of the oxide growth is related to the C-H_n bonds. We suggested that most of the C-H_n bonds were bonded to Si with n = 3, that gave rise to voids to facilitate the oxidation of amorphous silicon carbide films.

In this paper, we report the Inductive Coupled Plasma (ICP) etching of RF sputtered unhydrogenated amorphous silicon carbide film (a-Si_0.5C_0.5), and plasma enhanced chemical vapour deposited (PECVD) hydrogenated amorphous silicon carbide films (a-Si_0.3C_0.7:H and a-Si_0.7C_0.3:H), asprepared and annealed, using CF₄/O₂ chemistry. The etch rate of amorphous SiC is observed to be closely related to the hydrogen content. The mechanism of etching is studied by varying the RIE power, ICP power and pressure. It has been suggested that the removal of surface polymers (CF_x) is a key factor in the etching process. In order to study the difference in etch rate between sputtered and PECVD SiC and the effects of changing Si/C ratio, IR spectra are used to reveal the bonds density in the samples.

X-ray reflectivity (XRR) is a sensitive and non-destructive technique for the characterization of surfaces and thin film properties. Due to the spectroscopic nature of the problem, the unknown parameters are solved indirectly by fitting the theoretical reflectivity spectra to the experimental spectra. In this work, we propose three algorithms that allow the direct determination of the properties, which are more efficient compared to the fitting process that requires initial guesses, and whose convergence depends critically on the goodness of the guesses. The algorithms are developed for a structure with a one-layer film on a substrate. However, for films having an additional top surface layer, or an interface layer next to the substrate, the algorithms can also be applied to approximately deduce the parameters of the main layer of film.

In the plastic molding industry, plastic parts like pager and handphone cases, plastic containers, etc. are formed in a mold by applying temperature and pressure. The transfer molding is the standard workhorse for the electronics industry. Although the transfer molding is widely used, it is far from being optimized. Mold sticking is a serious practical problem in this industry. A solution to the problem is to apply mold-releasing agents on the mold to act as a lubricant layer between the plastic and the mold. This easily results in stains and degraded surface finish. This paper investigates the effectiveness of solid thin films on reducing the adhesion between polymer and mold steel of different surface roughness. WS₂, MoS₂, and DLC coatings are deposited on test surfaces via unbalanced magnetron sputtering before polymer blocks are molded on and pulled apart using an Instron Machine. The force required to separate the plastic part and the mold steel is used as an indication of the stickiness. After the separation, the coating surface is also examined under microscope for stains and polymer residues. The coatings are characterized using Raman spectroscopy and contact angle measurements. Generally, the stickiness increases with initial surface roughness for all coatings. Initial test indicates that the DLC coating has the highest contact angle with water (100°) and the best anti-sticking properties among the samples tested, and could reduce the stickiness by 80% as compared to bare steel.

The success of crystalline GaN as an optical and electronic material has motivated an enormous effort to explore all aspects of the material. Little is known and reported about the amorphous phase of this semiconducting wide band gap material. In this paper, we report on the properties of amorphous GaN (a-GaN) grown on p-Si at 443K using electron cyclotron resonance (ECR) plasma-assisted metalorganic chemical vapor deposition (MOCVD). Silicon is a potential alternative to sapphire due to its high quality and readily available as a large diameter and low cost substrates. The film was analyzed by a variety of methods, including scanning electron microscopy (SEM), atomic force microscopy (AFM) and x-ray diffraction (XRD). The current-voltage characteristics of a-GaN/Si heterojunction were measured from room temperature to 363K. Rectification behavior and photovoltaic effect were observed for this anisotype heterojunction. The electrical characteristics of Ni Schottky barriers on a-GaN were also investigated.

The carbon nitride films were deposited on single crystalline Si(001) and polycrystalline diamond substrates using microwave plasma chemical vapor deposition (MPCVD) with CH₄+N₂ as well as CH₄+NH₃ mixtures as the reactive gas source, respectively. Different CH₄/N₂ and CH₄/NH₃ gas ratios were tested. The results showed that carbon nitride films with different nitrogen content could more readily be obtained using a mixture of CH₄/N₂ rather than CH₄/NH₃. The films grown by different CH₄/N₂ ratios showed different morphology, which was revealed by scanning electron microscopy (SEM). The crystalline carbon nitride films containing silicon were realized using a CH₄:N₂ = 1:100 ratio. X-ray photoelectron spectroscopy (XPS), Auger electron microscopy (AES), Raman spectroscopy, and X-ray diffraction were used to characterize the composition and chemical bonding of the deposited films.

We report on the efficient photoluminescence (PL) and optical properties of hydrogenated amorphous carbon thin films codoped with nitrogen and trimethylboron (TMB) grown by rf plasma-enhanced chemical vapor deposition at room temperature. The study clearly shows the observation of discrete PL emission peaks. The PL intensity of the film deposited with 20 sccm TMB is more than 10³ times than that of the film deposited without TMB. The change of optical bandgap and PL emission energy with TMB flow rate are discussed based on sp³ and sp² C networks. Angular dependence of the PL spectra revealed that the origin of multiple sharp peaks is due to Fabry-Perot cavity interference effect.

Using first-principles calculation, we have investigated the stability of various possible structures for hypothetical carbon phosphide solids with composition C₃P₄. Unlike C₃N₄, the calculations predict that pseudocubic-C₃P₄ is energetically favored relative to α-C₃P₄ and β-C₃P₄. The pseudocubic phase has bulk modulus of 230 GPa, highest among the various structures considered.

Carbon nitride (CN_x) thin films have been synthesized by hot filament assisted r.f. plasma-enhanced chemical vapor deposition with negative bias methods on Si (100) substrates. The influences on the thin film structure and hardness characteristics of r.f. power and substrate negative bias have been emphatically investigated. The optimal preparation parameters have been summarized as follows: r.f. power of 200W, substrate negative bias of -200V, substrate temperature of about 600°C, total reactive gas pressure of about 110Pa, flow ratio of CH₄ to N₂ of 1 : 5.5.

Infrared and effusion of hydrogen, as well as of the inert gases, were studied for dc magnetron sputtered a-Si:C:H films. A structural transition from compact to void-rich material is observed and attributed to hydrogen-induced void formation. Inert gas atoms were incorporated into the material by ion implantation. It is shown that the inert gas effusion spectra give the information about sizes of microstructure.

Cubic boron nitride films (c-BN) were prepared by sputtering of a hexagonal BN sintered target. The films obtained were characterized by scanning electron microscopy, Infrared absorption spectra and UV-visible transmission spectra. The UV photodetetor devices of c-BN films were fabricated by photolithographic techniques. The devices exhibited a large photocurrent when exposed to light with a wavelength less than 223nm. The results obtained also show that the photoconductive properties closely depend on the deposition conditions. The photoconductive gain for the sample deposited at r. f. power of 300W was greater than that of the sample prepared at r. f. Power of 100W. This can be ascribed to that the carrier lifetime and mobility of the films have been improved.

Emission spectra from the ECR plasma enhanced magnetron sputtering discharge used for CN_x film deposition were investigated in the wavelength range 350 – 550 nm. The optical emission spectra from both the negative glow discharge zone near the target surface and the plasma zone formed by ECR discharge and magnetron discharge were studied separately. The dominant chemical species in both zone were found to be N₂⁺, N₂^*, and CN radicals. But the intensity of CN radical in the plasma zone was greater than that in the negative zone, where an emission band of C₂ was detected. The dependence of the intensities of CN band on the working gas pressure was investigated, and the formation of CN radicals, which could be vital in the CN_x film deposition process, was discussed. It was shown that a possible mechanism could be the reaction of N₂⁺ and N₂ with C₂ in the gas phase.

The application of carbon nitride as a barrier against copper diffusion was investigated. Amorphous carbon nitride (a-CN) thin films were prepared on Si(100) substrates by rf magnetron sputtering of graphite target in N₂ plasma. A thin Cu layer was then deposited in-situ atop of the a-CN film. Annealing process was carried out in nitrogen (N₂) ambient at the temperature of 400°C and 600°C respectively. The as-deposited and annealed films were characterized by x-ray photoelectron spectroscopy (XPS). The measurements show that both sp²C-N and sp³-N bonds were formed in the as-deposited carbon nitride films. The compositional analyses indicate that the deposited a-CN thin film is able to act as an effective diffusion barrier against copper at annealing temperature up to 400°C.

An attempt for modification of carbon nitride material by introduction of Al to form a ternary Al-C-N compound in a thin film deposited using inductively coupled plasma (ICP) assisted DC magnetron sputtering is reported. Optical emission spectroscopy (OES) is used for in-situ observation and identification of reactive species. The films were characterized using x-ray photoelectron spectroscopy (XPS) and x-ray diffraction spectroscopy (XRD). The results indicate that C-N bond is formed in the plasma. The XPS narrow scam spectra confirm the existence of C-Al, sp²C-N and sp³C-N bonds. Elemental proportion of carbon increases with the CH₄/N₂ flow rate ratio, and has a tendency to saturate. The film is dominated by c-AlN (111), mixed with Al₄C₃ and AlCN ternary compound.

Carbon nitride thin films were prepared by cathodic electrodeposition. The dicyandiamide compound dissovled in acetone was selected as the organic precursor. Single crystal silicon wafers and conductive glass (ITO) wafers were used as substrates. XPS measurements indicated that the films composed of carbon and nitrogen elements. The nitrogen content reached 41%. The polycrystalline β-C₃N₄ should exit in the prepared film from TED measurements. The nano hardness of the films on ITO substrates were as high as 13 GPa. The structure and properties were studies.

Control and diagnostics of low-frequency (~ 500 kHz) inductively coupled plasmas for chemical vapor deposition (CVD) of nano-composite carbon nitride-based films is reported. Relation between the discharge control parameters, plasma electron energy distribution/probability functions (EEDF/EEPF), and elemental composition in the deposited C-N based thin films is investigated. Langmuir probe technique is employed to monitor the plasma density and potential, effective electron temperature, and EEDFs/EEPFs in Ar + N₂ + CH₄ discharges. It is revealed that varying RF power and gas composition/pressure one can engineer the EEDFs/EEPFs to enhance the desired plasma-chemical gas-phase reactions thus controlling the film chemical structure. Auxiliary diagnostic tools for study of the RF power deposition, plasma composition, stability, and optical emission are discussed as well.

We report the successful synthesis of crystalline carbon nitride by chemical vapor deposition of certain nitrogen containing organic precursors. The precursor is heated and the vapors enter the hot deposition zone where they are pyrolysed and deposited in the form of thin films over pretreated substrates. The powder x-ray diffraction analysis shows clear peaks corresponding to the carbon nitride crystals of tetragonal form in addition to a broad hump corresponding to the amorphous nitrogenated carbon. The crystallites size is ~300Å and the volume fraction of the crystallites is about ~7%. The optimum conditions of preparation are found out. The Infrared spectra of these samples also suggest the formation of Carbon Nitride crystals. The analysis reconfirms that the material contains crystallites of Carbon Nitride embedded in an amorphous matrix of nitrogenated carbon. Further the material is characterized by C,H,N elemental analysis, EDX and Raman spectra. Since all the above analyses probe the bulk material, the background amorphous matrix in this case, expecting a clear evidence of nanometer sized crystallites from these tests are unlikely. Attempts are being made to increase the yield of these carbon nitride crystallites.