Boron-Doped Diamond Films Deposited on Silicon Substrates by MPCVD

High quality, good adhesion and p-type diamond films are obtained by microwave plasma chelincal vapordeposition. The area of the films is 20 x 20 nun. The structural morphologies, bonding mechanism and surfacemol'Phology are characterized by X-ray diffraction (XRD), Raman scattering and scanning Electron microscopy(SEM) respectively. The resistance, Hall coefficient, mobility, etc. are also measured. Tile factors related tonucleation and other properties of diamond films are discussed.

Application of Boron-doped Diamond Film Electrode in Fast Detection of Samonella in Water

[Objective] The study aimed to discuss the application of boron-doped diamond （BDD） film electrode in fast detection of samonella in water. [ Method] Boron-doped diamond film electrode was prepared and used as the working electrode in fast detection of salmonella in water using chronoamberometry, and the oxidation mechanism of the electrode acting on salmonella was discussed. [ Result] Compared with traditional biologi- cal methods, chronoamperometry could detect the number of salmonellae in water more simply, rapidly and sensitively. [ Conclusion] The method of using BDD electrode to detect salmonella quantity will be widely applied in future.

Direct and Simultaneous Determination of Phenol, Hydroquinone and Nitrophenol at Boron-Doped Diamond Film Electrode

The electrochemical characteristics of multi-component phenolic pollutants, such as phenol （Ph）, hydroquinone （HQ） and 4-nitrophenol （4-NP）, were investigated on boron-doped diamond （BDD） film electrode by differential pulse voltammetry （DPV） technique. A simple and feasible platform was accordingly established for the direct and simultaneous determination of these three phenolic pollutants. Results showed that, Ph, HQ and 4-NP gave obvious oxidation peaks on BDD electrode at the potential of 1.24, 0.76 and 1.52 V, respectively. Each of them displayed good linear relationship between their oxidation peak currents and their corresponding concentrations in a rather wide range coexisting with one or two of the other phenolic pollutants. The detection limits of Ph, HQ and 4-NP were estimated to be as low as 1.82×10^-6, 1.67×10^-6 and 1.44×10^-6 mol·L^-1, respectively. Therefore, a promising direct and simultaneous electrochemical determination method of multi-component phenolic pollutants in wastewater samples was constructed successfully on BDD electrode with advantages being rapid, simple, convenient, sensitive, in situ and inexpensive.

Electrochemical Characteristics and Applications of Boron-Doped Polycrystalline Diamond Film Electrodes

The elcetrochemical characteristics of boron doped polycrystalline diamond thin film (BDF) electrode 4×4 mm 2 in size were studied using cyclic voltammetry and potentiostatic method. The diamond electrode exhibits adequate electrochemical activity and its response current changes linearly with K 3Fe(CN) 6 concentrations. The response current is proportional to the square root of the scan rate, reflecting mass transport controlled by planar diffusion. Stable mass transport can be quickly established within 4s. The BDF electrode provides good resolving power for the determination of lead and cadmium and gives satisfactory results in the analysis of pure water sample.

Effect of nitrogen on deposition and field emission properties of boron-doped micro-and nano-crystalline diamond films

In this paper,we report the effect of nitrogen on the deposition and properties of boron doped diamond films synthesized by hot filament chemical vapor deposition.The diamond films consisting of micro-grains(nano-grains) were realized with low(high) boron source flow rate during the growth processes.The transition of micro-grains to nano-grains is speculated to be strongly(weekly) related with the boron(nitrogen) flow rate.The grain size and Raman spectral feature vary insignificantly as a function of the nitrogen introduction at a certain boron flow rate.The variation of electron field emission characteristics dependent on nitrogen is different between microcrystalline and nanocrystalline boron doped diamond samples,which are related to the combined phase composition,boron doping level and texture structure.There is an optimum nitrogen proportion to improve the field emission properties of the boron-doped films.

Plasma Processing of Boron-Doped Nano-Crystalline Diamond Thin Film Fabricated on Poly-Crystalline Diamond Thick Film

Plasma treatments of boron-doped nano-crystalline diamond （NCD） thin films were carried out in order to improve their electrical properties of the films. Boron-doped NCD thin films were fabricated on well polished poly-crystalline diamond （PCD） thick films in a microwave plasma enhanced chemical vapor deposition （MPCVD） reactor, then they were processed in methane, ar- gon, hydrogen and B2H~ （0.1% diluted by H~） plasmas, respectively. Scanning electron microscopy （SEM） and atomic force microscope （AFM） results show that the surface morphology changed lit- tle during the 10 min treatment. Secondary ion mass spectroscopy （SIMS） results indicate that B2H6 plasma was efficient for increasing boron concentration in NCD films, while the carrier anal- yses demonstrates that CH4 plasma processing was effective to activate the dopants and resulted in good electrical properties.

Ohmic and Schottky contacts of hydrogenated and oxygenated boron-doped single-crystal diamond with hill-like polycrystalline grains

Hill-like polycrystalline diamond grains(HPDGs)randomly emerged on a heavy boron-doped p+single-crystal diamond(SCD)film by prolonging the growth duration of the chemical vapor deposition process.The Raman spectral results confirm that a relatively higher boron concentration(~1.1×10^(21) cm^(-3))is detected on the HPDG with respect to the SCD region(~5.4×10^(20) cm^(-3)).It demonstrates that the Au/SCD interface can be modulated from ohmic to Schottky contact by varying the surface from hydrogen to oxygen termination.The current-voltage curve between two HPDGs is nearly linear with either oxygen or hydrogen termination,which means that the HPDGs provide a leakage path to form an ohmic contact.There are obvious rectification characteristics between oxygen-terminated HPDGs and SCD based on the difference in boron doping levels in those regions.The results reveal that the highly boron-doped HPDGs grown in SCD can be adopted as ohmic electrodes for Hall measurement and electronic devices.

Electrochemical incineration of dimethyl phthalate by anodic oxidation with boron-doped diamond electrode

The anodic oxidation of aqueous solutions containing dimethyl phthalate （DMP） up to 125 mg/L with sodium sulfate （Na2SO4） as supporting electrolyte within the pH range 2.0-10.0 was studied using a one-compartment batch reactor employing a boron-doped diamond （BDD） as anode. Electrolyses were carded out at constant current density （1.5-4.5 mA/cm^2）. Complete mineralization was always achieved owing to the great concentration of hydroxyl radical （-OH） generated at the BDD surface. The effects of pH, apparent current density and initial DMP concentration on the degradation rate of DMP, the specific charge required for its total mineralization and mineralization current efficiency were investigated systematically. The mineralization rate of DMP was found to be pH-independent and to increase with increasing applied current density. Results indicated that this electrochemical process was subjected, at least partially, to the mass transfer of organics onto the BDD surface. Kinetic analysis of the temporal change of DMP concentration during electrolysis determined by High Performance Liquid Chromatography （HPLC） revealed that DMP decay under all tested conditions followed a pseudo first-order reaction. Aromatic intermediates and generated carboxylic acids were identified by Gas Chromatography- Mass Spectrometry （GC-MS） and a general pathway for the electrochemical incineration of DMP on BDD was proposed.

Comparative study of oxidation ability between boron-doped diamond (BDD) and lead oxide (PbO_2) electrodes

The electrochemical oxidation capabilities of two high-performance electrodes,the boron-doped diamond film on Ti （Ti/BDD） and the lead oxide film on Ti （Ti/PbO2）,were discussed.Hydroxyl radicals （·HO） generated on the electrode surface were detected by using p-nitrosodimethylaniline （RNO） as the trapping reagent.Electrochemical oxidation measurements,including the chemical oxygen demand （COD） removal and the current efficiency （CE）,were carried out via the degradation of p-nitrophenol （PNP） under the galvanostatic condition.The results indicate that an indirect reaction,which is attributed to free hydroxyl radicals with high activation,conducts on the Ti/BDD electrode,while the absorbed hydroxyl radicals generated at the Ti/PbO2 surface results in low degradation efficiency.Due to quick mineralization which combusts PNP to CO2 and H2O absolutely by the active hydroxyl radical directly,the CE obtained on the Ti/BDD electrode is much higher than that on the Ti/PbO2 electrode,notwithstanding the number of hydroxyl radicals produced on PbO2 is higher than that on the BDD surface.

Synthesis and characterization of p-type boron-doped IIb diamond large single crystals

High-quality p-type boron-doped IIb diamond large single crystals are successfully synthesized by the temperature gradient method in a china-type cubic anvil high-pressure apparatus at about 5.5 GPa and 1600 K. The morphologies and surface textures of the synthetic diamond crystals with different boron additive quantities are characterized by using an optical microscope and a scanning electron microscope respectively. The impurities of nitrogen and boron in diamonds are detected by micro Fourier transform infrared technique. The electrical properties including resistivities, Hall coefficients, Hall mobilities and carrier densities of the synthesized samples are measured by a four-point probe and the Hall effect method. The results show that large p-type boron-doped diamond single crystals with few nitrogen impurities have been synthesized. With the increase of quantity of additive boron, some high-index crystal faces such as {113} gradually disappear, and some stripes and triangle pits occur on the crystal surface. This work is helpful for the further research and application of boron-doped semiconductor diamond.

Effect of substrate temperature on the growth and properties of boron-doped microcrystalline silicon films

Highly conductive boron-doped hydrogenated mieroerystalline silicon （μc-Si：H） films are prepared by very high frequency plasma enhanced chemical vapour deposition （VHF PECVD） at the substrate temperatures （Ts） ranging from 90℃ to 270℃. The effects of Ts on the growth and properties of the films are investigated. Results indicate that the growth rate, the electrical （dark conductivity, carrier concentration and Hall mobility） and structural （crystallinity and grain size） properties are all strongly dependent on Ts. As Ts increases, it is observed that 1） the growth rate initially increases and then arrives at a maximum value of 13.3 nm/min at Ts=210℃, 2） the crystalline volume fraction （Xc） and the grain size increase initially, then reach their maximum values at TS=140℃, and finally decrease, 3） the dark conductivity （σd）, carrier concentration and Hall mobility have a similar dependence on Ts and arrive at their maximum values at Ts-190℃. In addition, it is also observed that at a lower substrate temperature Ts, a higher dopant concentration is required in order to obtain a maximum σd.

Synthesis of Boron-doped Diamond/Porous Ti Composite Materials——Effect of Carbon Concentration

Highly boron-doped diamond films were deposited on porous titanium substrates by hot filament chemical vapor deposition technique. The morphology variation of highly boron-doped diamond films grown on porous titanium substrates was investigated, and the effects of carbon concentration on nucleation density and diamond growth were also studied. The continuous change of surface morphology and structure of diamond film were characterized by scanning electron microscopy. The structures of diamond film and interlayer were analyzed by X-ray diffraction. The quality of boron-doped diamond film was confirmed by visible Raman spectroscopy. The experimental results reveal that surface morphology and quality of boron-doped diamond films are various due to the change of carbon concentration. The thickness of intermediate layer decreases with the carbon concentration increasing.

Effects of deposition pressure and plasma power on the growth and properties of boron-doped microcrystalline silicon films

Using diborane as doping gas, p-doped μc-Si：H layers are deposited by using the plasma enhanced chemical vapour deposition （PECVD） technology. The effects of deposition pressure and plasma power on the growth and the properties of μc-Si：H layers are investigated. The results show that the deposition rate, the electrical and the structural properties are all strongly dependent on deposition pressure and plasma power. Boron-doped μc-Si：H films with a dark conductivity as high as 1.42 Ω^-1·cm^-1 and a crystallinity of above 50% are obtained. With this p-layer, μc-Si：H solar cells are fabricated. In addition, the mechanism for the effects of deposition pressure and plasma power on the growth and the properties of boron-doped μc-Si：H layers is discussed.

Electrochemical Detection of Clenbuterol in Pig Liver at Pyrrole DNA Modified Boron-doped Diamond Electrode

The direct detection of clenbuterol（CL） in pig liver without any extraction separation at a pyrrole-DNA modified boron-doped diamond（BDD） electrode is reported. The pyrrole-DNA modified BDD electrode has a strong electrocatalytic effect on the redox reaction of CL. One oxidization and two reduction peaks of CL appear at 340. 2, 299. 8 and 166. 6 mV（ versus SCE）, respectively. The pyrrole polymer alone cannot electrocatalyze the above reaction at a BDD electrode ; the electrocatalytic effect of a BDD electrode modified with DNA membrane is unsufficient for the analytical detection of CL; the replacement of boron-doped diamond by glass carbon makes the electrocatalytic reaction impossible ; the redox process is pH dependent. The influences of various experimental parameters on the pyrrole-DNA modified BDD electrode were investigated. A sensitive cyclic vohammetric response for CL was obtained in a linear range from 3.4 × 10^-6 to 5 × 10^ -4 mol/L with a detection limit of 8.5 × 10^-7 mol/L. A mean recovery of 102. 7% of CL in the pig liver sample solution and a reproducibility of 3.2% were obtained.

Electroanalytical Investigation on Paracetamol on Boron-Doped Diamond Electrode by Voltammetry

An electroanalytical method was developed for the direct quantitative determination of paracetamol in tablets based on its oxidation behavior. The electrochemical oxidation and determination of paracetamol were easily carried out on born-doped diamond (BDD) electrode using two voltammetric techniques (CV and DPV). The electrochemical measurements performed by cyclic voltammetric (CV) and differential pulse voltammetry (DPV) techniques were carried out using a cathodically pretreated boron-doped diamond electrode in HClO4 and KClO4 electrolytes. HClO4 was then selected for analytical purposes and scan rate studies were also completed. The oxidation of the paracetamol is found to be irreversible and a diffusion-controlled nature of the paracetamol oxidation peak was established. A linear calibration curve for DPV analysis was constructed in the paracetamol concentration range from 0 μM to 13.87 μM, with 0.16 μM and 0.55 μM as the detection and quantification limit respectively.

Analytical Determination of Benzophenone-3 in Sunscreen Preparations Using Boron-Doped Diamond Electrodes

A new electroanalytical procedure was developed for the determination of Benzophenone-3 (BENZO) in commercial sunscreen as the active ingredient. The procedure is based on the use of electrochemical methods as cyclic and square-wave voltammetry, with boron-doped diamond (BDD) electrodes. The reduction of BENZO in Britton-Robinson buffer (0.1 mol●L–1) using this type of electrode gives rise to one irreversible peak in –1.30 V (versus Ag/AgCl) in presence of cationic surfactant cetyltrimethylammonium bromide (CTABr). The proposed electrochemical method was successfully applied to the analysis of commercially available pharmaceutical preparations.

Numerical Analysis of Nd:YAG Pulsed Laser Polishing CVD Self-standing Diamond Film

Chemical vapor deposited （CVD） diamond film has broad application foreground in high-tech fields. But polycrystalline CVD self-standing diamond thick film has rough surface and non-uniform thickness that adversely affect its extensive applications. Laser polishing is a useful method to smooth self-standing diamond film. At present, attentions have been focused on experimental research on laser polishing, but the revealing of theoretical model and the forecast of polishing process are vacant. The paper presents a finite element model to simulate and analyze the mechanism of laser polishing diamond based on laser thermal conduction theory. The experimental investigation is also carried out on Nd：YAG pulsed laser smoothing diamond thick film. The simulation results have good accordance with the results of experimental results. The temperature and thermal stress fields are investigated at different incidence angles and parameters of Nd：YAG pulsed laser. The pyramidal-like roughness of diamond thick film leads to the non-homogeneous temperature fields. The temperature at the peak of diamond film is much higher than that in the valley, which leads to the smoothing of diamond thick film. The effect of laser parameters on the surface roughness and thickness of graphite transition layer is also carried out. The results show that high power density laser makes the diamond surface rapid heating, evaporation and sublimation after its graphitization. It is also found that the good polish quality of diamond thick film can be obtained by a combination of large incident angle, moderate laser pulsed energy, large repetition rate and moderate laser pulse width. The results obtained here provide the theoretical basis for laser polishing diamond film with high efficiency and high quality.

AFM Study on Interface of HTHP As-grown Diamond Single Crystal and Metallic Film

The study for the interface of as-grown diamond and metallic film surrounding diamond is an attractive way for understanding diamond growth mechanism at high temperature and high pressure (HTHP), because it is that through the interface carbon atom groups from the molten film are transported to growing diamond surface. It is of great interest to perform atomic force microscopy (AFM) experiment; which provides a unique technique different from that of normal optical and electron microscopy studies, to observe the interface morphology. In the present paper, we report first that the morphologies obtained by AFM on the film are similar to those of corresponding diamond surface, and they are the remaining traces after the carbon groups moving from the film to growing diamond. The fine particles and a terrace structure with homogeneous average step height are respectively found on the diamond (100) and (111) surface. Diamond growth conditions show that its growth rates and the temperature gradients in the boundary layer of the molten film at HTHP result in the differences of surface morphologies on diamond planes, being rough on (100) plane and even on the (111) plane. The diamond growth on the (100) surface at HPHT could be considered as a process of unification of these diamond fine particles or of carbon atom groups recombination on the growing diamond crystal surface. Successive growth layer steps directly suggest the layer growth mechanism of the diamond (111) plane. The sources of the layer steps might be two-dimensional nuclei and dislocations.

Simulations of the Dependence of Gas Physical Parameters on Deposition Variables during HFCVD Diamond Films

During the growth of the hot filament chemical vapor deposition （HFCVD） diamond films, numerical simulations in a 2-D mathematical model were employed to investigate the influence of various deposition parameters on the gas physical parameters, including the temperature, velocity and volume density of gas. It was found that, even in the case of optimized deposition parameters, the space distributions of gas parameters were heterogeneous due primarily to the thermal blockage come from the hot filaments and cryogenic pump effect arisen from the cold reactor wall. The distribution of volume density agreed well with the thermal round-flow phenomenon, one of the key obstacles to obtaining high growth rate in HFCVD process. In virtue of isothermal boundary with high temperature or adiabatic boundary condition of reactor wall, however, the thermal roundflow was profoundly reduced and as a consequence, the uniformity of gas physical parameters was considerably improved, as identified by the experimental films growth.

Microwave CVD Thick Diamond Film Synthesis Using CH4/H2/H2O Gas Mixtures

Thick diamond films with a thickness of up to 1.2 mm and a area of 20 cm^2 have been grown in a homemade 5 kW microwave plasma chemical vapor deposition （MPCVD） reactor using CH4/H2/H2O gas mixtures. The growth rate, radial profiles of the film thickness, diamond morphology and quality were evaluated with a range of parameters such as the substrate temperature of 700℃ to 1100℃, the fed gas composition CH4/H2 = 3.0%, H2O/H2 = 0.0%,-2.4%. They were characterized by scanning electron microscopy and Raman spectroscopy. Translucent diamond wafers have been produced without any sign of non-diamond carbon phases, Raman peak as narrow as 4.1 cm^-1. An interesting type of diamond growth instability under certain deposition conditions was observed in a form of accelerated growth of selected diamond crystallites of a very big lateral size, about 1 mm, and of a better structure compared to the rest of the film.