掺硼金刚石薄膜的电化学性能

利用循环伏安法,通过对比掺硼金刚石薄膜电极和铂／金刚石电极分别作为工作电极时的循环伏安曲线,分析了两种电极表现出的电化学性能差别,并利用能级理论进行了机理探讨。结果表明掺硼金刚石薄膜电极具有宽的电化学窗口（宽度约为3V）、良好的化学稳定性和极低的背景电流（接近0）,是一种较有潜力的电化学电极材料。     

Effect of B/C ratio on the physical properties of highly boron-doped diamond films

Highly boron-doped diamond films were deposited on silicon substrate by hot filament chemical vapor deposition in a gas mixture of hydrogen and methane. The chemical bonding states, surface texture, and electrical resistivity of these films were analyzed by X-ray photoelectron spectroscopy, scan electron microscope, and four-point probe method. It was found that boron dopants play an important role in the texture and chemical bonding states of the diamond films. An appropriate concentration of boron dopants (B/C ratio of 10 000 ppm) can simultaneously improve crystal quality and reduce resistivity of the diamond films. The minimum resistivity of diamond films reaches 1.12 × 10⁻² Ω cm, which is applicable as electrodes.     

Synthesis, structure, and field emission properties of sulfur-doped nanocrystalline diamond

The synthesis and properties of sulfur-doped nanocrystalline diamond films were investigated. The films were deposited by hot-filament chemical vapor deposition on Mo substrates using methane, hydrogen, and hydrogen disulfide. The nanocrystalline nature of the material arises from the induction of continuous secondary nucleation in the chemical vapor deposition environment. Complementary characterization tools were employed in order to obtain a comprehensive and coherent understanding of the correlations between the structural and electronic properties. In particular, sulfur-doped nanocrystalline diamond films show n-type Hall conductivity, enhanced field emission properties, and insensitivity to ion radiation. It was found that n-type doping of the tetragonally-bonded carbon matrix together with a nano network of trigonally-bonded carbon are crucial elements for enhanced field emission from nanocrystalline diamond. These conclusions and the corresponding supporting evidence are discussed.     

High-pressure,high-temperature processing of low-nitrogen boron-doped diamond

We have studied high-pressure, high-temperature processing (7.0 GPa, 2000–2100°C) of low-nitrogen boron-doped synthetic diamonds grown in the Fe-Ni-C system (5.5–6.0 GPa, 1350–1450°C) with boron and titanium additions. The results indicate that, during the growth of low-nitrogen boron-doped diamonds, there is a competition between different acceptors (boron and nickel). The system of point defects and their distribution over the crystal are not influenced by the processing; the uniformity of coloration in natural diamonds is governed by the prevalence of octahedron growth sectors.     

Optical and electrochemical properties of optically transparent,boron-doped diamond thin films deposited on quartz

The optical and electrochemical properties of transparent, boron-doped diamond thin film, deposited on quartz, are discussed. The films were deposited by microwave-assisted chemical vapor deposition, for 1-2 h, using a 0.5% CH4/H2 source gas mixture at 45 Torr and 600 W of power. A high rate of diamond nucleation was achieved by mechanically scratching the quartz. This pretreatment leads to the formation of a continuous film, in a short period of time, which consists of nanometer-sized grains of diamond. The thin-film electrode was characterized by cyclic voltammetry, atomic force microscopy, and UV-visible absorption spectrophotometry. The film's electrochemical response was evaluated using Ru(NH3)6(3+/2+) in 1 M KCl, Fe(CN)6(3-/4-) in 1 M KCl, and chlorpromazine (CPZ) in 10 mM HClO4. The film exhibited a low voltammetric background current and a stable and active voltammetric response for all three redox systems. The optical transparency of the polycrystalline film in the visible region was near 50% and fairly constant between 300 and 800 nm. The optical and electrical properties were extremely stable during 48-h exposure tests in various aqueous (HNO3, NaOH) solutions and nonaqueous (e.g., chlorinated) solvents. The properties were also extremely stable during anodic and cathodic potential cycling in harsh aqueous environments. This stability is in stark contrast to what was observed for an indium-doped tin oxide thin film coated on quartz. The spectroelectrochemical response (transmission mode) for CPZ was studied in detail, using a thin-layer spectroelectrochemical cell. Thin-layer voltammetry, potential step/ absorption measurements, and detection analytical figures of merit are presented. The results demonstrate that durable, stable, and optically transparent diamond thin films, with low electrical resistivity (approximately 0.026 omega x cm) laterally through the film, can be deposited on quartz.     

Electronic structure of boron-doped diamond with B–H complex and B pair

The electronic structure of boron–hydrogen complex and boron pair in diamond are studied by first-principles density-functional calculations with supercell models. The electronic structure calculated for the B–H complexes with C_2v or C_3v symmetry and the nearest-neighbor B pair is used to interpret recent experimental results such as B 1s x-ray photoemission spectroscopy, ¹¹B nuclear quadruple resonance and B K-edge x-ray absorption spectroscopy, which cannot be explained solely by the isolated substitutional boron.     

Synthesis,structure, and some physical properties of carbon and chromium deposits possessing a fractal structure

Experimental data obtained by scanning electron microscopy show that a carbon deposit formed during graphite spraying in an electric arc and chromium particles obtained by electrochemical deposition under certain conditions possess similar fractal structures. Data on some physical properties, the size of fractal aggregates, and the fractal dimensions of carbon and chromium deposits are presented. A possible mechanism of the fractal structure formation is discussed.     

Structure and superconductivity of isotope-enriched boron-doped diamond

Abstract

Superconducting boron-doped diamond samples were synthesized with isotopes of ¹⁰B, ¹¹B, ¹³C and ¹²C. We claim the presence of a carbon isotope effect on the superconducting transition temperature, which supports the ‘diamond-carbon’-related nature of superconductivity and the importance of the electron–phonon interaction as the mechanism of superconductivity in diamond. Isotope substitution permits us to relate almost all bands in the Raman spectra of heavily boron-doped diamond to the vibrations of carbon atoms. The 500 cm^?1 Raman band shifts with either carbon or boron isotope substitution and may be associated with vibrations of paired or clustered boron. The absence of a superconducting transition (down to 1.6 K) in diamonds synthesized in the Co–C–B system at 1900 K correlates with the small boron concentration deduced from lattice parameters.     

Structure and superconductivity of isotope-enriched boron-doped diamond

Superconducting boron-doped diamond samples were synthesized with isotopes of ¹⁰B, ¹¹B, ¹³C and ¹²C. We claim the presence of a carbon isotope effect on the superconducting transition temperature, which supports the ‘diamond-carbon’-related nature of superconductivity and the importance of the electron–phonon interaction as the mechanism of superconductivity in diamond. Isotope substitution permits us to relate almost all bands in the Raman spectra of heavily boron-doped diamond to the vibrations of carbon atoms. The 500 cm⁻¹ Raman band shifts with either carbon or boron isotope substitution and may be associated with vibrations of paired or clustered boron. The absence of a superconducting transition (down to 1.6 K) in diamonds synthesized in the Co–C–B system at 1900 K correlates with the small boron concentration deduced from lattice parameters.     

掺硼金刚石膜的制备及其应用

金刚石虽然具有极为优异的性能,如具有很大的能隙,高的电子迁移率、空穴迁移率和高热导率,以及负的电子亲和势,但要将它用于半导体材料时还不能直接使用,必须要先进行金刚石的P型和n型掺杂。因此,研究金刚石的P型和n型掺杂具有很重要的现实意义。在金刚石薄膜中掺杂时,一般是掺入硼原子以实现P型掺杂,掺入氮原子或磷原子以实现n型掺杂。然而,由于N和P在金刚石中的施主能级太深,现在n型掺杂金刚石薄膜制备尚不成功,这是金刚石实用化的障碍。本文介绍了金刚石膜掺硼目的、方法和制备,总结了掺硼金刚石膜在微电子、电化学、光电子、工具等领域应用状况以及存在问题。     

Synthesis, structure, and physical properties of carbon, iron, and chromium deposits possessing a fractal structure

A carbon deposit formed during graphite spraying in an electric arc, as well as iron and chromium particles obtained by electrochemical deposition under certain conditions, possess fractal structures. Data on some physical properties, the size of fractal aggregates, and the fractal dimension D of carbon, iron, and chromium deposits are presented. Relations between the fractal dimensions and physical properties of deposits are considered. A possible mechanism of the fractal structure formation is discussed.     

Metal-to-insulator transition and superconductivity in boron-doped diamond

The experimental discovery of superconductivity in boron-doped diamond came as a major surprise to both the diamond and the superconducting materials communities. The main experimental results obtained since then on single-crystal diamond epilayers are reviewed and applied to calculations, and some open questions are identified. The critical doping of the metal-to-insulator transition (MIT) was found to coincide with that necessary for superconductivity to occur. Some of the critical exponents of the MIT were determined and superconducting diamond was found to follow a conventional type II behaviour in the dirty limit, with relatively high critical temperature values quite close to the doping-induced insulator-to-metal transition. This could indicate that on the metallic side both the electron-phonon coupling and the screening parameter depend on the boron concentration. In our view, doped diamond is a potential model system for the study of electronic phase transitions and a stimulating example for other semiconductors such as germanium and silicon.     

Hydrothermal synthesis, characterization and properties of TiO2 nanorods on boron-doped diamond film

The rutile TiO₂ nanorods have been hydrothermally synthesized on boron-doped diamond (BDD) film with a ZnO buffer layer. It is demonstrated that the ZnO buffer layer plays a key role in increasing the density and improving the morphology of synthesized TiO₂ nanorods. The heterojunction of n-TiO₂ nanorods/p-BDD shows an evident rectifying behavior with a ratio of ∼ 180 at 6 V. Experimentally, the TiO₂ nanorod-covered BDD exhibits an improved electron field-emission property over that without using a ZnO buffer layer.     

Vertically aligned nanowires from boron-doped diamond

Vertically aligned diamond nanowires with controlled geometrical properties like length and distance between wires were fabricated by use of nanodiamond particles as a hard mask and by use of reactive ion etching. The surface structure, electronic properties, and electrochemical functionalization of diamond nanowires were characterized by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) as well as electrochemical techniques. AFM and STM experiments show that diamond nanowire etched for 10 s have wire-typed structures with 3-10 nm in length and with typically 11 nm spacing in between. The electrode active area of diamond nanowires is enhanced by a factor of 2. The functionalization of nanowire tips with nitrophenyl molecules is characterized by STM on clean and on nitrophenyl molecule-modified diamond nanowires. Tip-modified diamond nanowires are promising with respect to biosensor applications where controlled biomolecule bonding is required to improve chemical stability and sensing significantly.     

大尺寸掺硼宝石级金刚石单晶的高温高压合成及电学性质研究

在5.4GPa、1200～1400℃条件下,进行掺硼金刚石单晶的合成研究。成功合成出了重0.2g,径向尺寸达6.0mm的优质掺硼金刚石单晶。考察了合成体系中硼添加量对晶体透光度的影响。利用伏安特性和霍尔测试,得到了掺硼金刚石单晶常温电阻率、霍尔系数及霍尔迁移率和合成体系中硼添加量的关系。研究发现,随着合成体系中硼添加量的增加,晶体的电阻率和霍尔迁移率都呈下降趋势;霍尔系数随硼添加量的增加先下降后上升。随着硼添加量的增加:晶体常温电阻率下降,表明硼杂质已进入到金刚石晶体中。霍尔迁移率的下降,可能是晶体缺陷增多对载流子散射所致。霍尔系数先减小后增大,这可能与进入金刚石的硼元素量增大及晶体缺陷增多有关。     

Magnetic and electrical characterization of heavily boron-doped diamond

For a heavily boron-doped diamond (BDD) film, temperature variations of the electrical conductivity σ and magnetic susceptibility χ are reported. The room temperature σ 143 (Ω-cm)⁻¹ corresponds to a carrier concentration 10³ ppm, and its temperature variation yields an activation energy E_a 28 meV from 140 to 300 K and E_a0.88 meV from 40 to 80 K. It is argued that larger boron doping leads to lower magnitudes of E_a. The χ vs. T data (1.8–350 K) fits the Curie–Weiss law, with the concentration of paramagnetic species 120 ppm and a diamagnetic susceptibility −0.4×10⁻⁶ emu/g Oe. The results obtained from the measurements of σ and χ are discussed and compared.     

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

The electrochemical properties of doped diamond electrodes (10¹⁷–10¹⁹ B cm^− 3) grown on carbon fiber cloths in H₂SO₄ 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.     

Standard electrochemical behavior of high-quality, boron-doped polycrystalline diamond thin-film electrodes

Standard electrochemical data for high-quality, boron-doped diamond thin-film electrodes are presented. Films from two different sources were compared (NRL and USU) and both were highly conductive, hydrogen-terminated, and polycrystalline. The films are acid washed and hydrogen plasma treated prior to use to remove nondiamond carbon impurity phases and to hydrogen terminate the surface. The boron-doping level of the NRL film was estimated to be in the mid 1019 B/cm3 range, and the boron-doping level of the USU films was approximately 5 x 10(20) B/cm(-3) based on boron nuclear reaction analysis. The electrochemical response was evaluated using Fe-(CN)6(3-/4-), Ru(NH3)6(3+/2+), IrCl6(2-/3-), methyl viologen, dopamine, ascorbic acid, Fe(3+/2+), and chlorpromazine. Comparisons are made between the apparent heterogeneous electron-transfer rate constants, k0(app), observed at these high-quality diamond films and the rate constants reported in the literature for freshly activated glassy carbon. Ru(NH3)6(3+/2+), IrCl6(2-/3-), methyl viologen, and chlorpromazine all involve electron transfer that is insensitive to the diamond surface microstructure and chemistry with k0(app) in the 10(-2)-10(-1) cm/s range. The rate constants are mainly influenced by the electronic properites of the films. Fe(CN)6(3-/4-) undergoes electron transfer that is extremely sensitive to the surface chemistry with k0(app) in the range of 10(-2)-10(-1) cm/s at the hydrogen-terminated surface. An oxygen surface termination severely inhibits the rate of electron transfer. Fe(3+/2+) undergoes slow electron transfer at the hydrogen-terminated surface with k0(app) near 10(-5) cm/s. The rate of electron transfer at sp2 carbon electrodes is known to be mediated by surface carbonyl functionalities; however, this inner-sphere, catalytic pathway is absent on diamond due to the hydrogen termination. Dopamine, like other catechol and catecholamines, undergoes sluggish electron transfer with k0(app) between 10(-4) and 10(-5) cm/s. Converting the surface to an oxygen termination has little effect on k0(app). The slow kinetics may be related to weak adsorption of these analytes on the diamond surface. Ascorbic acid oxidation is very sensitive to the surface termination with the most negative Ep(ox) observed at the hydrogen-terminated surface. An oxygen surface termination shifts Ep(ox) positive by some 250 mV or more. An interfacial energy diagram is proposed to explain the electron transfer whereby the midgap density of states results primarily from the boron doping level and the lattice hydrogen. The films were additionally characterized by scanning electron microscopy and micro-Raman imaging spectroscopy. The cyclic voltammetric and kinetic data presented can serve as a benchmark for research groups evaluating the electrochemical properties of semimetallic (i.e., conductive), hydrogen-terminated, polycrystalline diamond.     

11B nuclear magnetic resonance in boron-doped diamond

Abstract

This review summarizes recent results obtained by ¹¹B solid-state nuclear magnetic resonance (NMR) on boron-doped diamond, grown by the high-pressure high-temperature (HPHT) or chemical vapor deposition techniques. Simple single-pulse experiments as well as advanced two-dimensional NMR experiments were applied to the boron sites in diamond. It is shown that magic-angle spinning at magnetic fields above 10 T is suitable for observation of high-resolution ¹¹B spectra of boron-doped diamond. For boron-doped HPHT diamonds, the existence of the excess boron that does not contribute to electrical conductivity was confirmed and its ¹¹B NMR signal was characterized. The point-defect structures (B+H complexes and -B-B-/-B-C-B- clusters), postulated previously for the excess boron, were discarded and graphite-like structures were assigned instead.     

Electrochemical degradation of chlorobenzene on boron-doped diamond and platinum electrodes

In this paper the electrochemical degradation of chlorobenzene (CB) was investigated on boron-doped diamond (BDD) and platinum (Pt) anodes, and the degradation kinetics on these two electrodes was compared. Compared with the total mineralization with a total organic carbon (TOC) removal of 85.2% in 6 h on Pt electrode, the TOC removal reached 94.3% on BDD electrode under the same operate condition. Accordingly, the mineralization current efficiency (MCE) during the mineralization on BDD electrode was higher than that on the Pt electrode. Besides TOC, the conversion of CB, the productions and decay of intermediates were also monitored. Kinetic study indicated that the decay of CB on BDD and Pt electrodes were both pseudo-first-order reactions, and the reaction rate constant (k_s) on BDD electrode was higher than that on Pt electrode. The different reaction mechanisms on the two electrodes were investigated by the variation of intermediates concentrations. Two different reaction pathways for the degradation of CB on BDD electrode and Pt electrode involving all these intermediates were proposed.