Properties Of Boron-doped Diamond Films Research Articles

Effects of oxygen/nitrogen co-incorporation on regulation of growth and properties of boron-doped diamond films

Regulation with nitrogen and oxygen co-doping on growth and properties of boron doped diamond films is studied by using laughing gas as dopant. As the concentration of laughing gas (N2O/C) increases from 0 to 10%, the growth rate of diamond film decreases gradually, and the nitrogen-vacancy (NV) center luminescence intensity increases first and then weakens. The results show that oxygen in laughing gas has a strong inhibitory effect on formation of NV centers, and the inhibitory effect would be stronger as the concentration of laughing gas increases. As a result, the film growth rate and nitrogen-related compensation donor decrease, beneficial to increase the acceptor concentration (∼3.2 × 1019 cm−3) in the film. Moreover, it is found that the optimal regulation with the quality and electrical properties of boron doped diamond films could be realized by adding appropriate laughing gas, especially the hole mobility (∼700 cm2/V⋅s), which is beneficial to the realization of high-quality boron doped diamond films and high-level optoelectronic device applications in the future.

Diamond/Porous Titanium Nitride Electrodes With Superior Electrochemical Performance for Neural Interfacing.

Robust devices for chronic neural stimulation demand electrode materials which exhibit high charge injection (Qinj) capacity and long-term stability. Boron-doped diamond (BDD) electrodes have shown promise for neural stimulation applications, but their practical applications remain limited due to the poor charge transfer capability of diamond. In this work, we present an attractive approach to produce BDD electrodes with exceptionally high surface area using porous titanium nitride (TiN) as interlayer template. The TiN deposition parameters were systematically varied to fabricate a range of porous electrodes, which were subsequently coated by a BDD thin-film. The electrodes were investigated by surface analysis methods and electrochemical techniques before and after BDD deposition. Cyclic voltammetry (CV) measurements showed a wide potential window in saline solution (between −1.3 and 1.2 V vs. Ag/AgCl). Electrodes with the highest thickness and porosity exhibited the lowest impedance magnitude and a charge storage capacity (CSC) of 253 mC/cm2, which largely exceeds the values previously reported for porous BDD electrodes. Electrodes with relatively thinner and less porous coatings displayed the highest pulsing capacitances (Cpulse), which would be more favorable for stimulation applications. Although BDD/TiN electrodes displayed a higher impedance magnitude and a lower Cpulse as compared to the bare TiN electrodes, the wider potential window likely allows for higher Qinj without reaching unsafe potentials. The remarkable reduction in the impedance and improvement in the charge transfer capacity, together with the known properties of BDD films, makes this type of coating as an ideal candidate for development of reliable devices for chronic neural interfacing.

Gas Composition Influence on the Properties of Boron-Doped Diamond Films Deposited on the Fused Silica

Abstract The main subject of this study are molecular structures and optical properties of boron-doped diamond films with [B]/[C]ppm ratio between 1000 and 10 000, fabricated in two molar ratios of CH4-H2mixture (1 % and 4 %). Boron-doped diamond (BDD) film on the fused silica was presented as a conductive coating for optical and electronic purposes. The scanning electron microscopy images showed homogenous and polycrystalline surface morphology. The Raman spectroscopy confirmed the growth of sp3 diamond phase and sp2carbon phase, both regular and amorphous, on the grain boundaries, as well as the efficiency of boron doping. The sp3/sp2ratio was calculated using the Raman spectra deconvolution method. A high refractive index (in a range of 2.0 to 2.4 at λ= 550 nm) was achieved for BDD films deposited at 700 °C. The values of extinction coefficient were below 1.4 at λ= 550 nm, indicating low absorption of the film

Effect of deposition temperature on properties of boron-doped diamond films on tungsten carbide substrate

Abstract Boron-doped diamond (BDD) films were deposited on the tungsten carbide substrates at different substrate temperatures ranging from 450 to 850 °C by hot filament chemical vapor deposition (HFCVD) method. The effect of deposition temperature on the properties of the boron-doped diamond films on tungsten carbide substrate was investigated. It is found that boron doping obviously enhances the growth rate of diamond films. A relatively high growth rate of 544 nm/h was obtained for the BDD film deposited on the tungsten carbide at 650 °C. The added boron-containing precursor gas apparently reduced activation energy of film growth to be 53.1 kJ/mol, thus accelerated the rate of deposition chemical reaction. Moreover, Raman and XRD analysis showed that heavy boron doping (750 and 850 °C) deteriorated the diamond crystallinity and produced a high defect density in the BDD films. Overall, 600–700 °C is found to be an optimum substrate temperature range for depositing BDD films on tungsten carbide substrate.

Morphology and Structure Properties of Boron-doped Diamond Films Prepared by Hot Cathode Direct Current Plasma Chemical Vapor Deposition

Boron-doped diamond (BDD) films were deposited by hot cathode direct current plasma chemical vapor deposition (HCDC-PCVD) according to various mixture ratios of CH4/H2/B(OCH3)3 gas. The Raman performances and surface morphologies of the BDD films were then characterized by Raman spectroscopy and scanning electron microscopy (SEM). Results indicated that the flow rate of B(OCH3)3 had marked effects on the growth characteristics of the produced boron-doped diamond films. The presence and concentration of the doped boron atoms significantly altered both the surface morphologies and structures of the diamond films. With increasing flow rate of B(OCH3)3, the crystal grain surfaces became smooth as visible under SEM. The B-doping levels in these films increased from 1.75×1019cm-3 to a maximum of 2.4×1021cm-3, estimated from the Raman spectra. DOI: http://dx.doi.org/10.5755/j01.ms.22.2.12923

Growth Rate and Electrochemical Properties of Boron-Doped Diamond Films Prepared by Hot-Filament Chemical Vapor Deposition Methods

Growth Rate and Electrochemical Properties of Boron-Doped Diamond Films Prepared by Hot-Filament Chemical Vapor Deposition Methods

RETRACTED ARTICLE: The Impact of Improved Nucleation Layer on the Properties of Boron-Doped Diamond Films

In this study, diamond films were synthesized on directed Si and improved nucleation nano-iron layer Si substrates using B2O3 in ethanol and hydrogen gas mixture by hot filament chemical vapor deposition method. To investigate the role of catalyst in purity, cluster size, growth rate and conductivity of grown boron-doped films, the boron to carbon ratio was constant. Raman spectroscopy, field emission scanning electron microscopy and four point probe techniques were applied to characterize the properties of films. It was found that nano-iron layer leads to deposit boron-doped diamond film with better structural quality as well as more effective boron doping concentration. This rising in the conductivity of the grown film on Fe-coated substrate can be mainly attributed to the catalytic activity of iron to increase the diamond cluster size as well as reduce the formation of pores and amorphous phases. Moreover, a 25 % increase in film thickness assisted by iron-catalyst was observed.

Preparation, characterization and electrochemical properties of boron-doped diamond films on Nb substrates

A series of boron-doped polycrystalline diamond films were prepared by hot filament (HF) chemical vapor deposition on Nb substrates. The effects of B/C ratio of reaction gas on film morphology, growth rate, chemical bonding states, phase composition and electrochemical properties of each deposited sample were studied by scanning electron microscopy, Raman spectra, X-ray diffraction, microhardness indentation, and electrochemical analysis. Results show that the average grain size of diamond and the growth rate decrease with increasing the B/C ratio. The diamond films exhibit excellent adhesion under Vickers microhardness testing (9.8 N load). The sample with 2% B/C ratio has a wider potential window and a lower background current as well as a faster redox reaction rate in H2SO4solution and KFe(CN)6 redox system compared with other doping level electrodes.

ボロンドープしたＣＶＤダイヤモンド膜の機械的特性評価

For this study, single-crystal and polycrystalline diamond films with different boron contents were synthesized in a hot-filament chemical vapor deposition (CVD) apparatus to evaluate the mechanical properties of these films. Boron was added to the diamond by introducing B(CH3)3 :trimethyl boron diluted to 1000 ppm with hydrogen into the diamond-synthesis atmosphere. The synthesized diamond film's crystallinity was evaluated using Raman spectroscopy. The Hertz fracture strength was measured using a diamond-ball indenter. Furthermore, the wear resistance of the film was evaluated using a wear testing machine.The results indicate that the crystallinity of the single-crystal diamond film increased concomitantly with increasing boron content. Furthermore, the Hertz fracture strength increased by 20% with the addition of boron. Results clarified that the wear volume of polycrystalline diamond film decreased to approximately one-third its usual value by the addition of boron. These results show that the mechanical properties of boron-doped diamond films can be improved considerably by adding an appropriate amount of boron.

Effect of gas composition on the growth and electrical properties of boron-doped diamond films

Boron-doped diamond films are synthesized by the hot-filament chemical vapor deposition (HFCVD) method via introduction of the gas mixtures of methane and hydrogen, as well as the boron precursor carried by H 2 through a B(OCH 3) 3 liquid, into the chamber. Boron-doping level in as-grown diamond films can be well controlled in the range from 10 19 to 10 21 cm − 3 by adjusting the B/C ratios of gas mixtures. The morphology, structure and resistivity of as-grown diamond films are investigated with scanning electron microscopy (SEM), X-ray diffraction (XRD) and Hall measurement system. The results show that the crystal quality and carrier concentration and resistivity of the as-grown films are obviously dependent on the B/C ratio of the gas mixtures during the deposition process. A critical B/C ratio of 3:4 is found to correspond to the highest crystal quality, highest carrier concentration and smallest film resistivity of as-grown boron-doped diamond films, which should be mainly related with the effective doping ability. In addition, based on the growth kinetics of the diamond films, the effect of the boron-doping on the growth process is discussed in detail.

Morphological and electrochemical properties of boron-doped diamond films on carbon cloths with enhanced surface area

The electrochemical properties of doped diamond electrodes (10 17–10 19 B cm − 3 ) grown on carbon fiber cloths in H 2SO 4 0.1 mol L − 1 electrolyte were investigated. Cyclic voltammograms of B-doped diamond/carbon fiber cloth and carbon fiber cloth electrodes showed that both kinds of electrodes possess similar working potential windows of about 2.0 V. The electrode capacitance was determined by impedance spectroscopy and chronopotentiometry measurements and very close values were obtained. The capacitance values of the diamond film on carbon fiber cloths were 180 times higher than the ones of diamond films on Si. In this paper we have also discussed the capacitance frequency dependence of diamond/carbon cloth electrodes.

Electrical properties of boron-doped diamond films synthesized by MPCVD on an iridium substrate

Boron-doped diamond films were synthesized on an iridium substrate by microwave plasma-assisted chemical vapor deposition, using trimethylboron as the dopant source. The Ir substrate was bias-treated by the constant-current mode to permit the formation of oriented diamond nuclei. In order to isolate the B-doped diamond layer electrically from the Ir substrate, the non-doped diamond particles that were formed were grown in the 〈1 0 0〉 and then 〈1 1 1〉 directions and finally, a B-doped layer was synthesized to give a B/C ratio of 100–400 ppm. Surface morphology, Hall mobility and hole concentration were investigated for the resulting B-doped diamond films. The Hall mobility was closely related to the surface morphology of the diamond films. After optimizing the synthesis conditions, a Hall mobility of 340 cm −2 V −1 s −1 and hole concentration of 2×10 10 at 250 K was obtained for a heteroepitaxial B-doped diamond film synthesized at a B/C ratio of 200 ppm. These values are smaller than previously reported values for homoepitaxial B-doped diamond film.

Surface morphology and electrical properties of boron-doped diamond films synthesized by microwave-assisted chemical vapor deposition using trimethylboron on diamond (100) substrate

Prime novelty: The smoothness of the synthesized boron-doped diamond was improved by the pre-treatment of a hydrogen plasma. Moreover, the Hall mobility also increased with this pre-treatment. Surface morphology and electrical properties, such as electrical conductivity, hole concentration and Hall mobility, were investigated for boron-doped diamond films, which were synthesized by microwave-assisted chemical vapor deposition (MPCVD) on a (100) diamond substrate. Trimethylboron (TMB) was used as a dopant source and methane (CH4) was used as a carbon source. The morphology of the synthesized diamond surface depended on the MPCVD conditions such as TMB and CH4 concentrations in the gas phase, and lower concentrations of TMB and CH4 lead to a smoother surface. When the substrate was treated in a hydrogen plasma, the electrical properties of the boron-doped diamond films, as well as the smoothness of the surface, were improved. After optimizing the synthesis conditions, Hall mobility reached to 2020 cm2 V−1 s−1 at 243 K for a diamond film with a hole concentration of 5×1012 cm−3.

Defect structure and electron field-emission properties of boron-doped diamond films

The correlation between electron field-emission properties of diamond films prepared by the chemical vapor deposition (CVD) process and the defect structure induced by boron doping was examined. Secondary ion mass spectroscopic analysis indicates that the solubility limit of boron in diamond is (B3+)2=5×1021 cm−3, whereas the infrared absorption (IR) spectroscopic analysis reveals that the largest boron concentration that can be incorporated as substitutional dopants is only one tenth of the solubility limit, (B3+)d=5×1020 cm−3. Including boron species higher than this concentration induces large strain and atomic defects, which are inferred by the distorted Raman resonance peak, noisy IR spectra, and twinned microstructure for diamond. Presumably, the presence of atomic defects, which behave as electron traps, is the mechanism deteriorating the electron field-emission properties of CVD diamonds.

Effect of nitrogen incorporation on electrical properties of boron-doped diamond films

The effect of a small amount of nitrogen incorporated in chemical vapor deposited diamond films on their electrical properties was studied. Upgrading the purity of CH4 gas from the conventional ultra-high purity to the grade with no detection of nitrogen resulted in improvement of electrical properties of the boron-doped homoepitaxial diamond films; the Hall mobility was increased by 4.3 times at the room temperature. Decrease in nitrogen concentration in the diamond films was confirmed by investigating the 2.16 eV center of cathodoluminescence induced by ion beam irradiation and subsequent annealing.

Negative electron affinity observed in boron-doped p-type diamond films by scanning field emission spectroscopy

Field emission properties of boron-doped diamond films were studied by combined scanning tunneling microscopy/spectroscopy and scanning field emission spectroscopy. A detailed spatial correlation between field emission sites and diamond morphology, surface work function, and diamond quality can be established by this technique. A possible indication of negative electron affinity of the (111) faces near the (111)/(111) and (111)/(100) grain boundaries and high defect sites of boron doped p-type diamond films were observed by field emission I–V (current–voltage) measurement.

Electrical properties of boron-doped diamond films prepared by microwave plasma chemical vapour deposition

The electrical properties of boron-doped (B-doped) diamond films prepared by microwave plasma chemical vapour deposition (CVD) were measured in the temperature range 77–900 K. The temperature dependence of the electrical resistivity ρ was attributed to the activation energy ∈ h ∼ 0.35 eV in the high temperature region and ∈ 1 ∼ 0.05 eV in the low temperature region. The ∈ 1 value agreed well with the reported value for boron acceptors in diamond. The transitional temperature T 0 at which the value of the activation energy changed from ∈ 1, to ∈ h decreased with increasing substrate temperature ( T s) during CVD diamond growth from 230 K at T s=840°C to 160 K at T S=900°C. An increase in the Hall mobility μ and reduction in the compensation ratio N D/ N A were also observed with increasing substrate temperature. The piezoresistive properties of strain gauges composed of B-doped CVD diamond films were also investigated.

STUDY OF BORON-DOPED DIAMOND FILMS BY HOT FILAMENT CVD

The properties of boron-doped diamond films prepared by hot filament CVD were studied with Raman spectra and X-ray microanalysis. It was found that the content of the graphitic type （Ｓｐ2)bonding in the CVD diamond was reduced at low boron concentrations, and the widening and shift of the characteristic diamond Ｓｐ3 Raman peak appeared in the diamond with increasing boron concentrations. This can be interpreted in terms of the lattice strain and Fano interaction caused by boron doping.

Electrical properties of boron-doped diamond films after annealing treatment

Abstract Trimethylborate (B(OCH 3 ) 3 ) was used to obtain boron-doped (p-type) polycrystalline diamond thin films on a silicon substrate using microwave plasma-assisted chemical vapor deposition. The effect of the doping agent (trimethylborate) was characterized in terms of electrical properties, and the current-voltage ( I-V ) characteristics of the boron-doped diamond films using aluminum as contacts at room temperature were examined. A surprising result was that annealing improved the electrical properties of boron-doped diamond films. As the boron concentration increased, the forward current decreased because of the effects of impurity scattering, and the I-V characteristics were still rectified. After the samples were annealed in a helium ambient at 900 °C for 30 min, the I-V characteristics changed: the higher the concentration of boron in the doped diamond films, the more ohmic was the observed behavior. The differences in the I-V characteristics of annealed and non-annealed films were subsequently confirmed by Fourier transform infrared spectroscopy (FTIR), capacitance-voltage ( C-V ) measurements, and cathodoluminescence (CL) experiments. The results of these experiments demonstrated that the annealing treatment caused boron atoms initially in inactive sites (e.g. interstitial or clustering sites) to be incorporated into substitutional sites. The increase in substitutional boron atoms altered the I-V characteristics of the boron-doped diamond films.

Boron doped diamond films: Electrical and optical characterization and the effect of compensating nitrogen

Polycrystalline diamond films were prepared by microwave plasma assisted chemical vapour deposition from CH 4H 2 mixtures. For p-type doping with boron, trimethylborate was added at concentrations between 50 ppb and 500 ppm referred to the total gas phase. The boron concentration in the film, as determined by secondary ion mass spectrometry, varied between 1.1 × 10 18 cm −3 and 2.1 × 10 20 cm −3. A linear increase in the boron content in the film was observed for boron concentrations in the reactant gas up to 10 ppm. The boron incorporation saturates for gas phase concentrations of more than 50 ppm. For non-contact characterization of the doped films, Raman and Fourier transform spectroscopy were applied. With increasing boron concentration, the Raman spectra show an increasing asymmetry in the lineshape of the 1332 cm −1 zone centre optical phonon which is attributed to a Fano interference effect with the electronic continuum. Strong IR absorption around 3000 cm −1 due to acceptor ionization was observed and related to the boron concentration. Temperature dependent electrical measurements were taken to obtain information on the resistivity, mobility, activation energy and carrier concentration. Nitrogen is an omnipresent impurity in diamond and, as a deep donor, is able to compensate acceptors. In order to study the influence of nitrogen contamination, a series of diamond films with constant boron content and various nitrogen concentrations was prepared and characterized. The data reveal the strong influence of nitrogen on the properties of boron-doped diamond films. In particular, the conductivity is decreased by one order of magnitude, highlighting the compensating character of nitrogen in p-type doped diamond.