Microwave Plasma Chemical Vapor Deposition of Diamond Films on Silicon From Ethanol and Hydrogen

Diamond films with very smooth surface and good optical quality have been deposited onto silicon substrate using microwave plasma chemical vapor deposition (MPCVD) from a gas mixture of ethanol and hydrogen at a low substrate temperature of 450 ℃. The effects of the substrate temperature on the diamond nucleation and the morphology of the diamond film have been investigated and observed with scanning electron microscopy (SEM). The microstructure and the phase of the film have been characterized using Raman spectroscopy and X-ray diffraction (XRD). The diamond nucleation density significantly decreases with the increasing of the substrate temperature. There are only sparse nuclei when the substrate temperature is higher than 800 ℃ although the ethanol concentration in hydrogen is very high. That the characteristic diamond peak in the Raman spectrum of a diamond film prepared at a low substrate temperature of 450 ℃ extends into broadband indicates that the film is of nanophase. No graphite peak appeare

Characterization of Crystalline Nanoparticles/Nanorods Synthesized by Atmospheric Plasma Enhanced Chemical Vapor Deposition of Perfluorohexane

A mass of nanoparticles/nanorods were formed on a simultaneously deposited gran- ular film by plasma enhanced chemical vapor deposition （PECVD） of perfluorohexane at atmo- spheric pressure without any catalysts or templates. Scanning electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS） were used to characterize the morphology and the chem- ical compositions of nanoparticles. The average size of particles is about 100 nm and the length of synthesized nanorods is between 1 μm and 2.5/tm. The analyses of transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, selected area electron diffraction（SAED） and X-ray diffraction （XRD） reveals that the nanoparticles and nanorods are crystalline.

Characteristics and Electrical Properties of SiNx:H Films Fabricated by Plasma-Enhanced Chemical Vapor Deposition

SiNx：H films with different N/Si ratios are synthesized by plasma-enhanced chemical vapor deposition （PECVD）. Composition and structure characteristics are detected by Fourier transform infrared spectroscopy （FTIR） and X-ray photoelectron spectroscopy （XPS）. It indicates that Si-N bonds increase with increased NH3/SiH4 ratio. Electrical property investigations by I-V measurements show that the prepared films offer higher resistivity and less leakage current with increased N/Si ratio and exhibit entirely insulating properties when N/Si ratio reaches 0.9, which is ascribed to increased Si-N bonds achieved.

SYNTHESIS OF PPCuPc FILM BY MICROWAVE PLASMA CHEMICAL VAPORIZATION DEPOSITION(MPCVD)

Using a low power microwave generator(W_(max)=100W) and a Surfatron discharge device, Plasma-polymerized copper phthalocyanine (PPCuPc) film was synthesised from monomer copper phthalocyanine(CuPc) by microwave plasma chemical vaporization deposition(MPCVD) with Ar as incorporation gas. The film was characterized by FTIR and ESCA. The role of dissociation of chemical bond in the polymerization process and the influence of substrate temperature and material on deposition were investigated in some detail.

Preparation of Nano-Crystalline Diamond Films on Poly-Crystalline Diamond Thick Films by Microwave Plasma Enhanced Chemical Vapor Deposition

Nano-crystalline diamond （NCD） films were prepared on poly-crystalline diamond （PCD） thick flims by the microwave plasma enhanced chemical vapor deposition （MPCVD） method. Free standing PCD thick film （50 mm in diameter） with a thickness of 413 μm was deposited in CHn/H2 plasma. It was then abraded for 2 hours and finally cut into pieces in a size of 10×10 mm^2 by pulse laser. NCD fihns were deposited on the thick film substrates by introducing a micro-crystalline diamond （MCD） interlayer. Results showed that a higher carbon concentration （5%） and a lower substrate temperature （650℃） were feasible to obtain a highly smooth interlayer, and the appropriate addition of oxygen （2%） into the gas mixture was conducive to obtaining a smooth nano-crystalline diamond film with a tiny grain size.

Diagnosis of gas phase near the substrate surface in diamond film deposition by high-power DC arc plasma jet CVD

Optical emission spectroscopy （OES） was used to study the gas phase composition near the substrate surface during diamond deposition by high-power DC arc plasma jet chemical vapor deposition （CVD）. C2 radical was determined as the main carbon radical in this plasma atmosphere. The deposition parameters, such as substrate temperature, anode-substrate distance, methane concentration, and gas flow rate, were inspected to find out the influence on the gas phase. A strong dependence of the concentrations and distribution of radicals on substrate temperature was confirmed by the design of experiments （DOE）. An explanation for this dependence could be that radicals near the substrate surface may have additional ionization or dissociation and also have recombination, or are consumed on the substrate surface where chemical reactions occur.

Synthesis and Temperature-dependent Electrochemical Properties of Boron-doped Diamond Electrodes on Titanium

On the sand-blasting-treated titanium（Ti） substrate, the boron-doped diamond（BDD） electrodes with a wide potential window were prepared by microwave plasma chemical vapor deposition（MPCVD）. The electrochemi- cal oxidation ratios of phenol at BDD/Ti electrodes at elevated temperatures（from 20 ℃ to 80 ℃） were examined by the chemical oxygen demand（COD） of phenol electrolyte during electrolysis. The results show that the COD removal was increased at high temperatures and the optimized temperature for enhancing the electrochemical oxidation ratio of phenol is 60 ℃. The mechanism for the temperature-dependent electrochemical oxidation ratios of phenol at the electrodes was investigated. The study would be favorable for further improving the performance of BDD/Ti elec- trodes, especially working at high temperatures.

Preparation of TiO2/MCM-41 by plasma enhanced chemical vapor deposition method and its photocatalytic activity

Titanium dioxide is coated on the surface of MCM-41 wafer through the plasma enhanced chemical vapor deposition （PECVD） method using titanium isopropoxide （TTIP） as a precursor. Annealing temperature is a key factor affecting crystal phase of titanium dioxide. It will transform an amorphous structure to a polycrystalline structure by increasing temperature. The optimum anatase phase of TiO2 which can acquire the best methanol conversion under UV-light irradiation is obtained under an annealing temperature of 700℃ for 2 h, substrate tem- perature of 500~C, 70 mL. min1 of oxygen flow rate, and 100W of plasma power. In addition, the films are composed of an anatase-rutile mixed phase, and the ratio of anatase to rutile varies with substrate temperature and oxygen flow rate. The particle sizes of titanium dioxide are between 30.3 nm and 59.9nm by the calculation of Scherrer equation. Under the reaction conditions of ll6.8mg.L-1 methanol, 2.9mg.L-1 moisture, and 75~C of reaction temperature, the best conversion of methanol with UV-light is 48.2% by using the anatase-rutile （91.3/ 8.7） mixed phase TiO2 in a batch reactor for 60 min. While under fluorescent light irradiation, the best photoactivity appears by using the anatase-rutile （55.4/44.6） mixed phase TiO2 with a conversion of 40.0%.

Toughness enhancement of single-crystal diamond by the homoepitaxial growth of periodic nitrogen-doped nano-multilayers

Periodic nitrogen-doped homoepitaxial nano-multilayers were grown by microwave plasma chemical vapor deposition. The residual time of gases(such as CH4and N2) in the chamber was determined by optical emission spectroscopy to determine the nano-multilayer growth process, and thin, nanoscale nitrogen-doped layers were obtained. The highest toughness of 18.2 MPa·m^(1/2)under a Young’s modulus of1000 GPa is obtained when the single-layer thickness of periodic nitrogen-doped nano-multilayers is about 96 nm. The fracture toughness of periodic nitrogen-doped CVD layer is about 2.1 times that of the HPHT seed substrate. Alternating tensile and compressive stresses are derived from periodic nitrogen doping;hence, the fracture toughness is significantly improved. Single-crystal diamond with a high toughness demonstrates wide application prospects for high-pressure anvils and single-point diamond cutting tools.

Effect of initial precursor concentration on TiO_2 thin film nanostructures prepared by PCVD system

TiO2 thin film was prepared on Si substrate by plasma chemical vapor deposition （PCVD） system and the morphologies of ZiO2 thin film were controlled by adjusting the initial precursor concentration. As the initial titanium tetra-isopropoxide （TTIP） concentration increases in PCVD reactor, the shapes of TiO2 particles generated in PCVD reactor change from the spherical small-sized particles around 20 nm and spherical large-sized particles around 60 nm to aggregate particles around 100 nm. The TiO2 particles with different shapes deposit on the substrate and become the main building blocks of resulting TiO2 thin film. We observed the TiO2 thin film with smooth morphology at low initial TTIP concentration, granular morphology at medium initial TTIP concentration, and columnar morphology at high initial TTIP concentration. It is proposed that we can prepare the TiO2 thin film with controlled morphologies in one-step process just by adjusting the initial precursor concentration in PCVD .

Origin,characteristics,and suppression of residual nitrogen in MPCVD diamond growth reactor

Unintentional nitrogen incorporation has been observed in a set of microwave plasma chemical vapor deposition(MPCVD)-grown samples.No abnormality has been detected on the apparatus especially the base pressure and feeding gas purity.By a comprehensive investigation including the analysis of the plasma composition,we found that a minor leakage of the system could be significantly magnified by the thermal effect,resulting in a considerable residual nitrogen in the diamond material.Moreover,the doping mechanism of leaked air is different to pure nitrogen doping.The dosage of several ppm of pure nitrogen can lead to efficient nitrogen incorporation in diamond,while at least thousands ppm of leaked air is required for detecting obvious residual nitrogen.The difference of the dosage has been ascribed to the suppression effect of oxygen that consumes nitrogen.As the unintentional impurity is basically detrimental to the controllable fabrication of diamond for electronic application,we have provided an effective way to suppress the residual nitrogen in a slightly leaked system by modifying the susceptor geometry.This study indicates that even if a normal base pressure can be reached,the nitrogen residing in the chamber can be“activated”by the thermal effect and thus be incorporated in diamond material grown by a MPCVD reactor.

Significant suppression of residual nitrogen incorporation in diamond film with a novel susceptor geometry employed in MPCVD

This work proposed to change the structure of the sample susceptor of the microwave plasma chemical vapor deposition(MPCVD)reaction chamber,that is,to introduce a small hole in the center of the susceptor to study its suppression effect on the incorporation of residual nitrogen in the MPCVD diamond film.By using COMSOL multiphysics software simulation,the plasma characteristics and the concentration of chemical reactants in the cylindrical cavity of MPCVD system were studied,including electric field intensity,electron number density,electron temperature,the concentrations of atomic hydrogen,methyl,and nitrogenous substances,etc.After introducing a small hole in the center of the molybdenum support susceptor,we found that no significant changes were found in the center area of the plasma,but the electron state in the plasma changed greatly on the surface above the susceptor.The electron number density was reduced by about 40%,while the electron temperature was reduced by about 0.02 eV,and the concentration of atomic nitrogen was decreased by about an order of magnitude.Moreover,we found that if a specific lower microwave input power is used,and a susceptor structure without the small hole is introduced,the change results similar to those in the surface area of the susceptor will be obtained,but the spatial distribution of electromagnetic field and reactant concentration will be changed.

Effect of hydrogen content on dielectric strength of the silicon nitride film deposited by ICP-CVD

The inductively coupled plasma chemical vapor deposition(ICP-CVD) deposited silicon nitride(SiN_(x)) thin film was evaluated for its application as the electrical insulating film for a capacitor device.In order to achieve highest possible dielectric strength of SiN_(x),the process parameters of ICP-CVD were carefully tuned to control hydrogen in SiN_(x) films by means of tuning N_(2)/SiH_(4) ratio and radio frequency(RF) power.Besides electrical measurements,the hydrogen content in the films was measured by dynamic secondary ion mass spectrometry(D-SIMS).Fourier transform infrared spectroscopy(FTIR) and micro Raman spectroscopy were used to characterize the SiN_(x) films by measuring Si-H and N-H bonds’ intensities.It was found that the more Si-H bonds lead to the higher dielectric strength.

Effect of Particle Density on the Aligned Growth of Carbon Nanotubes

Aligned carbon nanotubes (CNTs) were prepared on Ni-coated Ni substrate by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at temperature of 550℃.The experimental results show a direct correlation between the alignment of CNTs and the density of the catalyst particles at low temperature.When the particle density is high enough,among CNTs there are strong interactions that can inhibit CNTs from growing randomly.The crowding effect among dense CNTs results in the aligned growth of CNTs at low temperature.

Preparation of Mo_(2)C by MPCVD and Its Photocatalytic Properties

Mo2C was prepared by microwave plasma chemical vapor deposition(MPCVD)technique with the power of 800 W and pressure of 18 kPa.Compared with traditional preparation methods,MPCVD has faster growth rate and higher purity of the products.The influence of growth time on the morphology and structure of Mo_(2)C was characterized by X-ray diffraction and Scanning Electron Microscopy.The photocatalytic performance of Mo_(2)C was tested.It was found that Mo_(2)C had good photocatalytic performance and the 6 h sample had the highest photodegradation rate,indicating the great potential of Mo_(2)C as photocatalyst.

Synthesis and Characteristics of Fe_3C Nanoparticles Embedded in Amorphous Carbon Matrix

We proposed a new way to synthesize a nanocomposite consisted of cementite Fe3C nanoparticles and amorphous carbon by radio frequency plasma-enhanced chemical vapor deposition. Transmission electron microscope images show the existence of nanometric dark grains（Fe3C） embedded in a light matrix（amorphous carbon） in the samples. X-ray photoelectron spectroscopy experiment exhibit that the chemical bonding state in the films corresponded to sp3/sp2 amorphous carbon, sp^3 C-N（287.3 eV） and C15 in Fe3C（283.5 eV）. With increasing deposition time, the ratio of amorphous carbon increased. The magnetic measurements show that the value of in-lane coercivity increased with increasing carbon matrix concentration（from about 6.56× 10^3 A/m for film without carbon structures to approximately 2.77× 10^4 and 5.81 × 10^4 AJm for nanocomposite films at room temperature and 10 K, respectively）. The values of saturation magnetization for the synthesized nanocomposites were lower than that of the bulk Fe3C （ 140 Am^2/kg）.

Preparation and characterization of carbon nano-sheet powders

Carbon nanosheet films were deposited on A1 substrates by using plasma assisted chemical vapor deposition （PACVD） technique. And after being peeled off from A1 substrates, carbon nanosheet powders （CNSPs） were obtained. In Raman spectrum of carbon film, there was a strong and broadened peak at about 1,580 cm^-1, indicating a carbon diamond-like film. Atomic force microscope image showed that the carbon diamond-like film had a grain size less than 100 nm, and its surface roughness Ra was 17.95 nm in an area of 5×5 μm^2. The CNSPs were irregular sheets with curly edges and a length of several micrometers to several hundreds of micrometers. The BET surface area of CNSPs was 6.66 m^2/g with no micro-pore present, which was confirmed by N2 adsorption-desorption characterization. In the adsorption testing, when the relative pressure p/po was higher than 0.3, the adsorption behavior did not follow the Langmuir equation. The addition of CNSPs to carbon black （catalyst support） could improve hydrodesulfurization performance of carbon supported Ni-W catalysts for diesel oil.

A simple method to synthesize worm-like AlN nanowires and its field emission studies

The worm-like AlN nanowires are fabricated by the plasma-enhanced chemical vapor deposition(PECVD)on Si substrates through using Al powder and N2 as precursors,CaF2 as fluxing medium,Au as catalyst,respectively.The as-grown worm-like AlN nanowires each have a polycrystalline and hexagonal wurtzite structure.Their diameters are about 300 nm,and the lengths are over 10μm.The growth mechanism of worm-like AlN nanowires is discussed.Hydrogen plasma plays a very important role in forming the polycrystalline structure and rough surfaces of worm-like AlN nanowires.The worm-like AlN nanowires exhibit an excellent field-emission(FE)property with a low turn-on field of 4.5 V/μm at a current density of 0.01 mA/cm^(2) and low threshold field of 9.9 V/μm at 1 mA/cm^(2).The emission current densities of worm-like AlN nanowires each have a good stability.The enhanced FE properties of worm-like AlN nanowires may be due to their polycrystalline and rough structure with nanosize and high aspect ratio.The excellent FE properties of worm-like AlN nanowires can be explained by a grain boundary conduction mechanism.The results demonstrate that the worm-like AlN nanowires prepared by the proposed simple and the PECVD method possesses the potential applications in photoelectric and field-emission devices.

Effect of Chamber Conditions and Substrate Type on PECVD of SiGeSn Films

In the past studies have shown that the addition of Ge and Sn into Si lattice to form SiGeSn enhances its carrier mobility and band-gap properties. Conventionally SiGeSn epitaxial films are grown using Ultra-High Vacuum (UHV) conditions with pressures ranging from 10-8 torr to 10-10 torr which makes high volume manufacturing very expensive. On the contrary, the use of low-pressure CVD processes (vacuum levels of 10-2 torr to 10-4 torr) is economically more viable and yields faster deposition of SiGeSn films. This study outlines the use of a cost-effective Plasma Enhanced Chemical Vapor Deposition (PECVD) reactor to study the impact of substrate temperature and substrate type on the growth and properties of polycrystalline SiGeSn films. The onset of polycrystallinity in the films is attributed to the oxygen-rich PECVD chamber conditions explained using the Volmer-Weber (3D island) mechanism. The properties of the films were characterized using varied techniques to understand the impact of the substrate on film composition, thickness, crystallinity, and strain.

Dependence of wet etch rate on deposition,annealing conditions and etchants for PECVD silicon nitride film

The influence of deposition, annealing conditions, and etchants on the wet etch rate of plasma enhanced chemical vapor deposition （PECVD） silicon nitride thin film is studied. The deposition source gas flow rate and annealing temperature were varied to decrease the etch rate of SiNx：H by HF solution. A low etch rate was achieved by increasing the SiH4 gas flow rate or annealing temperature, or decreasing the NH3 and N2 gas flow rate. Concentrated, buffered, and dilute hydrofluoric acid were utilized as etchants for Sit2 and SiNx：H. A high etching selectivity of Sit2 over SiNx：H was obtained using highly concentrated buffered HE