温度对n-ZnO/p-diamond薄膜异质结器件制备和电学性质的影响

采用反应磁控溅射法在p型硼掺杂金刚石(BDD)薄膜衬底上制备了非有意掺杂n型氧化锌(ZnO)薄膜。利用XRD、SEM、I-V特性曲线对n-ZnO/p-BDD薄膜复合结构进行表征分析。n-ZnO多晶膜沉积在p-BDD膜上形成了具有良好整流特性的异质结。在空气中对异质结进行退火处理,研究了退火(400℃,700℃)对异质结性质的影响。实验表明,较高退火温度处理,可获得多取向的ZnO膜,晶粒尺寸增大,n-ZnO/p-BDD异质结开启电压减小。不同温度下的电学性质测量结果证明该异质结适合在高温环境下工作。     

氢氧刻蚀对硼掺杂单晶金刚石质量的影响

本文利用微波等离子体化学气相沉积法,在未经过刻蚀处理以及经过氢氧刻蚀处理过的单晶金刚石籽晶上进行硼掺杂外延生长,目的是证明刻蚀处理对硼掺杂单晶金刚石生长形貌与质量的影响。     

热处理温度对铝酸锶长余辉薄膜结构和发光性能的影响

利用磁控溅射制备稀土掺杂铝酸锶薄膜前驱体,再将前驱体置于800℃、900℃、1000℃和1100℃弱还原气氛热处理,得到铝酸锶长余辉发光薄膜。薄膜的物相结构随热处理温度升高而发生改变,逐渐由SrAl₂O₄相转变为Sr₄Al₁₄O₂₅相,光致发光性能随之发生改变。     

掺硼金刚石薄膜的制备与研究

采用微波等离子体化学气相沉积技术在单晶硅、钛、钼、铌、钽基体上制备掺硼金刚石薄膜。分别采用X射线衍射仪、扫描电子显微镜、激光拉曼光谱仪、四探针电阻率测试仪研究其物相组成、表面形貌、晶体结晶性和电阻率。硼原子代替碳原子进入金刚石晶格中,产生更多的缺陷形核中心,导致掺硼金刚石薄膜的金刚石晶粒尺寸和电阻率随着掺硼浓度增加而减小。金刚石薄膜和基体间形成碳化物,金刚石在石墨层上形核生长。碳原子在不同基体中的扩散系数不同,导致硅基掺硼金刚石薄膜的晶粒尺寸更小且更加均匀,金属基体上的部分金刚石出现了异常长大的现象。采用该方法制备的掺硼金刚石薄膜的结晶性较好,由于基体热膨胀系数较金刚石大从而导致薄膜内部产生压应力,使得金刚石薄膜的D峰均向高波数偏移。     

CVD金刚石衬底上抗氧化、增透膜的制备与性能

采用射频磁控反应溅射法在化学气相沉积(chemical vapor deposition,CVD)的金刚石衬底上制备了AlN薄膜以及AlN/Si和AlN/Ge膜。通过X射线衍射分析了衬底加热温度对薄膜微结构的影响和薄膜高温下的氧化行为。结果表明:在衬底加热温度低于380℃时制备的AlN薄膜为非晶态,480℃时AlN薄膜为六方多晶。AlN薄膜在800℃热暴露后开始氧化,900℃时基本被氧化为Al2O3。在CVD金刚石上制备的AlN/Si和AlN/Ge膜都能提高金刚石在长波红外波段(8～10μm)的透过性能,单面最大增透分别为8%和3%。镀有AlN/Ge膜的CVD金刚石在800℃高温热暴露实验中,有AlN/Ge膜保护的金刚石表面未发生刻蚀。高温下AlN/Ge膜对金刚石有很好的保护作用,同时增透效果没有明显下降。     

掺硼浓度对金刚石薄膜电极电化学性能影响的研究

以不同掺硼浓度的金刚石薄膜作为电极材料,采用循环伏安法和交流阻抗法研究了电极的电化学性能,着重分析了掺硼浓度对金刚石电极电化学性能的影响.结果表明,随着掺硼浓度的增加,电极的电势窗口略微变小,背景电流也随之变大.在铁氰化钾电解液中,未掺杂金刚石薄膜的电极表面进行的不是可逆反应,而硼掺杂金刚石膜电极表面在反应过程中有着良好的活性和准可逆性;并且随着掺硼浓度的增加,其动力学过程主要受扩散过程控制.金刚石膜电极对苯酚模拟有机污染物的循环伏安实验表明,所考察的三个硼浓度不断增加的电极的氧化峰电流密度分别为0.8,1.9和5.1 mA(cm(2,说明在本实验范围内,金刚石膜电极对苯酚催化氧化作用随着掺硼浓度的增加而增强.     

甲烷浓度对金刚石薄膜(100)织构生长的影响

以H2和CH4的混合气体为气源,用微波等离子体辅助化学气相沉积法(MPECVD)在1 cm×1 cm S i(100)基体上沉积了金刚石薄膜。研究了不同的甲烷浓度对金刚石薄膜(100)织构生长趋势的影响。分别采用扫描电子显微镜(SEM),Ram an光谱对金刚石膜的表面形貌、质量进行了分析。结果表明,当基体温度为750℃,气压为4.8×103Pa,甲烷浓度为1.4%时,薄膜表面为(100)织构。     

BDD电极差分脉冲伏安法检测Cr(Ⅵ)离子

以氢气和甲烷为生长源,硼烷作掺杂源,采用微波等离子体化学气相沉积法(MPCVD)制备掺硼金刚石(BDD)薄膜电极,通过扫描电镜、拉曼光谱对其表面形貌、组成及结晶质量进行分析。将BDD电极作为工作电极,通过差分脉冲阳极溶出伏安法检测溶液中痕量Cr(Ⅵ)浓度。结果表明,BDD电极膜材中金刚石晶粒间密实均匀。而电极差分脉冲吸附溶出伏安法检测Cr(Ⅵ)信号在0.19×10-3~3.85×10-3mol/L范围内呈线性关系,电极检测限达到0.27×10-6mol/L。加入干扰离子后检测效果依然良好。最后,通过实验表明电极在pH=2时检测Cr(Ⅵ)效果较好。     

ZnMgO合金薄膜晶体质量与生长温度的依赖关系

利用等离子体分子辅助分子束外延设备在蓝宝石衬底上通过改变生长温度,得到了不同的ZnMgO合金薄膜。研究了衬底温度对ZnMgO的结构和光学性质的影响。X射线衍射谱表明所有的ZnMgO合金样品都是（002）取向。晶体结构为六角纤锌矿。随着生长温度的增加,ZnMgO的（002）衍射峰的最大半宽度逐渐减小。在ZnMgO合金中的Mg组分随衬底温度升高逐渐增大。样品的表面形貌随着衬底的温度改变而变化。ZnMgO的X射线衍射,透射光谱,光致发光谱和扫描电镜照片都表明在800℃得到了高质量的ZnMgO合金薄膜。并且通过控制衬底温度实现了ZnMgO中Mg组分的调节。     

工艺参数对金刚石薄膜显微结构与性能的影响

着重研究了甲烷浓度、基体温度等工艺参数对热丝CVD法金刚石薄膜显微结构与性能的影响。基体温度（低于1050℃）越高,甲烷浓度越低,膜中非金刚石碳的含量就越低,金刚石的晶形就越完整,晶粒也越大,因而金刚石薄膜的电阻率、初始氧化温度就越高。金刚石薄膜电阻率随温度升高而线性下降,电阻温度系数达2×1010Ω·cm／’℃。     

Grain boundary effect on the superconducting transition of microcrystalline boron-doped diamond films

Microcrystalline boron-doped diamond (BDD) films were prepared on silicon substrates by hot-filament chemical vapor deposition method. Different grain sizes of the boron-doped diamond films with nearly the same boron concentration were obtained by changing the nuclei concentration on the silicon substrates. The electrical transport behaviors of as-prepared boron-doped diamond films were measured, and the results revealed that with the increase of the grain sizes on the BDD films, the superconducting transition temperature was evidently increased. This phenomenon indicates that the superconducting transition of microcrystalline BDD films is influenced by the inhomogeneity aroused by the grain boundary effect. Our results could expand our understanding of the superconducting mechanism of microcrystalline BDD films, and are also significant to conventional applications of BDD materials.     

Effect of deposition temperature and quality of free-standing diamond substrates on the properties of RF sputtering ZnO films

Highly c-axis oriented ZnO film is often deposited on diamond substrates by RF magnetron sputtering and widely used for high frequency surface acoustic wave (SAW) devices. Deposition temperature is a key factor affecting the quality of the ZnO film. Different quality polished free-standing diamond films prepared by DC Arc Plasma Jet were used as the substrates to deposit ZnO films at different temperatures. Effect of the deposition temperature and the quality of the diamond films on the properties of the ZnO films were investigated by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that highly c-axis oriented ZnO films can be much easier deposited on the optical-grade diamond films with < 111> preferred orientation than the tool-grade diamond films with < 220> preferred orientation. The optimal deposition temperature is 200 °C for highly c-axis oriented and lower roughness ZnO films. Acoustic phase velocity of more than 10,000 m/s for the SAW devices based on the ZnO/optical-grade free-standing diamond films was obtained.     

Oxidation behaviour of high quality freestanding diamond films by high power arcjet operating at gas recycling mode

Oxidation may cause degradation of mechanical, thermal and optical properties of freestanding CVD diamond films at elevated temperatures, and thus may impose severe technical limitations for applications of freestanding diamond films. In the present investigation oxidation behaviour of high quality freestanding diamond films prepared by high power d.c. arc plasma jet operating at gas recycling mode has been studied. It was found by thermogravimetry that the diamond films started to oxidize at approximately 650 °C, whilst the rate of oxidation increased substantially with increasing temperatures. Experimental observations confirmed that grain boundaries were the most preferred site for oxidation damage. Detailed studies were made on the influence of high temperature oxidation on the optical, thermal, and mechanical properties of high quality freestanding diamond films. Our results demonstrated that the high quality freestanding films prepared by high power d.c. arcjet can be safely used below 800 °C for a short time period of 180 s, which is more than enough for certain important IR applications.     

High-quality homoepitaxial diamond (100) films grown under high-rate growth condition

We present advantages of high-power microwave plasma chemical vapor deposition (MPCVD) in homoepitaxial diamond film deposition. Diamond films grown at comparatively high growth rate of 3.5 μm/h showed intense free-exciton recombination emission at room temperature. The free-exciton decay time of the diamond film at room temperature, 22 ns, was much longer than that of type-IIa single crystal, indicating electronically high quality of the homoepitaxial films. Dislocation-related emissions were locally observed, a part of which created by mechanical polishing process was successfully removed by surface etching process using oxygen plasma. Another advantage of the high-power MPCVD is effective impurity doping; boron-doped diamond films with high carrier mobility and high carrier concentration were reproducibly deposited. An ultraviolet photodetector fabricated using the high-quality undoped diamond film showed lower noise equivalent power as well as higher photoresponsivity for ultraviolet light with better visible-blind property, compared to those of standard Si-based photodetectors. The high-power MPCVD is, thus, indispensable technique for depositing high quality diamond films for electronic devices.     

金刚石薄膜取向性和后处理对其辐X射响应性能的影响

采用微波等离子体化学气相沉积合成金刚石薄膜,通过优化工艺参数和原位等离子后处理等方法来提高金刚石薄膜的质量和辐射响应灵敏度.制作出三明治结构的辐射剂量计.研究了金刚石薄膜取向性和后处理对X射线辐射响应灵敏度的影响.结果表明:薄膜取向性和后处理对X辐射响应性能有很大影响.提高金刚石薄膜的纯度和取向性是提高X射线响应灵敏度的有效途径.制作的金刚石薄膜辐射剂量计的X射线响应电流与辐射剂量率间有良好的线性关系.在电阻率相近的情况下,[100]取向金刚石薄膜制成的器件X射线响应灵敏度比[111]取向的高,取向度越高,其辐射响应灵敏度也越高.原位氧等离子后处理金刚石薄膜剂量计的X射线响应灵敏度比原位氮、氢等离子后处理的高,薄膜表面金刚石的含量由69.9%提高到93.5%,辐射响应灵敏度较未处理的膜提高1倍以上.     

Electrochemical and morphological characterization of gold nanoparticles deposited on boron-doped diamond electrode

A novel two-step method was employed to synthesize gold nanoparticles dispersed on boron-doped diamond (BDD) electrode. It consisted of sputter deposition at ambient temperature of maximum 15 equivalent monolayers of gold, followed by a heat treatment in air at 600 °C. Gold nanoparticles with an average diameter between 7 and 30 nm could be prepared by this method on polycrystalline BDD film electrode. The obtained Au/BDD composite electrode appeared stable under conditions of electrochemical characterization performed using ferri-/ferrocyanide and benzoquinone/hydroquinone redox couples in acidic medium. The electrochemical behavior of Au/BDD was compared to that of bulk Au and BDD electrodes. Finally, the Au/BDD composite electrode was regarded as an array of Au microelectrodes dispersed on BDD substrate.     

Characterization of diamond fluorinated by glow discharge plasma treatment

The surface fluorination of diamond by treatment in glow discharge plasmas of CF₄ for different times has been investigated. High quality diamond films were deposited onto silicon substrates using hot filament chemical vapor deposition (HFCVD). Subsequently, the films were exposed to a radiofrequency glow discharge plasma of CF₄ for times ranging from 5 min to 1 h. The effects of the plasma treatment on the surface morphology, diamond quality and elemental composition were investigated using atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively. Differences in film roughness caused by the plasma treatment were detected by AFM and confirmed by scanning electron microscopy (SEM). Raman spectroscopic analyses showed that the original diamond was of high quality and that the bulk of each film was unchanged by the plasma treatment. Analyses using XPS revealed increased surface fluorination of the films at longer treatment times. In addition, the density of free radicals in the films was probed using electron paramagnetic resonance spectroscopy (EPRS), revealing that untreated diamond possesses an appreciable density of free radicals (6×10¹² g⁻¹) which initially falls with treatment time in the CF₄ plasma but increases for long treatment times.     

新型多孔Ti/BDD薄膜电极电化学氧化降解低浓度茜素红

运用热丝化学气相沉积（HFCVD）的方法制备了以多孔钛为基体的掺杂硼金刚石（porous Ti/BDD）薄膜电极,并测试了它的主要物理性质,SEM表明金刚石相生长良好并且能均匀地分布在基体表面和孔内,Raman光谱表明电极的金刚石相纯而且质量很高。采用循环伏安法研究了酸性条件下茜素红在多孔Ti/BDD电极上的电氧化行为。通过改变阳极电流密度、支持电解质Na2SO4的浓度来研究茜素红在多孔Ti/BDD电极上的电化学氧化降解的效果影响。结果表明：电流密度40 mA/cm2、支持电解质浓度0.5 mol/L为较理想的工艺参数,总电流效率达到30.2%。在相同条件下,发现多孔Ti/BDD薄膜电极氧化降解茜素红与平板Ti/BDD薄膜电极相比具有更高的电流效率。紫外可见光光谱证实了多孔Ti/BDD电极能够有效地电氧化降解茜素红。     

Electrochemical behavior of Au nanoparticle deposited on as-grown and O-terminated diamond electrodes for oxygen reduction in alkaline solution

Au nanoparticle was electrochemically deposited on both as grown and oxygen-terminated (O-terminated) boron-doped diamond (BDD) films. The surface coverages of Au nanoparticle were 0.07 and 0.18 corresponding to the areas of Au 0.012 and 0.029 cm², respectively, as noted from linear sweep voltammetry. The SEM studies indicated different morphologies of Au deposition such as random distribution of small spherical particles at both the grain boundaries and the facets on the as grown diamond film and clusters principally on the cross edges of two facets on the O-terminated diamond. The electrochemical behavior for oxygen reduction was examined using differential pulse voltammetry (DPV), which confirmed the higher catalytic efficiencies of Au deposited as grown and O-terminated BDD electrodes when compared to a polycrystalline Au electrode. Moreover, the mechanism of Au nanoparticle deposited BDD films for the oxygen reduction was investigated by ac impedance and hydrodynamic voltammetric methods.     

Dielectric property of thick freestanding diamond films by high power arcjet operating at gas recycling mode

Dielectric property of thick freestanding diamond films prepared by high power arcjet operating at gas recycling mode was measured by the high voltage electric bridge method at low frequencies (r.f.) and the wave guide resonance method at high frequencies (microwave). It was found that, with increasing frequencies, dielectric loss of freestanding diamond films increased at low frequencies, but decreased at high frequencies, with a maximum located at approximately 3 MHz. Measurements of dielectric loss of the freestanding diamond films at a microwave frequency of 5.2 GHz showed a strong dependence on the growth parameters such as substrate temperature and methane concentration. It was found that dielectric loss decreased with increasing substrate temperature, and increased with an increasing methane concentration in the feed gases. It is suggested that dielectric loss is closely related with the quality level of freestanding diamond film samples, as demonstrated by the results from Raman and SEM observations. Non-diamond carbon in the diamond films was found responsible for the increase in dielectric loss. Nitrogen was intentionally introduced into the Ar–H₂–CH₄ gas stream for diamond deposition to investigate the effect of impurities. It was shown that nitrogen addition to the feed gases seriously deteriorated the dielectric property of the resultant diamond films. This is again in agreement with our experimental observations by Raman and SEM, in that the addition of nitrogen also seriously deteriorated the quality of the diamond film. Mechanisms for the dielectric behaviour of the diamond films were discussed in detail.