Electroluminescence of double-doped diamond thin films

A new electroluminescence device is fabricated by microwave plasma chemical vapour deposition system and electron beam vapour deposition system. It is comprised of highly doped silicon/diamond/boron/nitrogen-doped diamond/indium tin oxide thin films. Effects of process parameters on morphologies and structures of the thin films are detected and analysed by scanning electron microscopy, Raman spectrometer and x-ray photoelectron spectrometer. A direct-current （DC） power supply is used to drive the electroluminescence device. The blue light emission with a luminance of 1.2 cd·m^-2 is observed from this double-doped diamond thin film electroluminescence device at an applied voltage of 105 V.

Adhesive strength of CVD diamond thin films quantitatively measured by means of the bulge and blister test

Large advancement has been made in understanding the nucleation and growth of chemical vapor deposition （CVD） diamond, but the adhesion of CVD diamond to substrates is poor and there is no good method for quantitative evaluation of the adhesive strength. The blister test is a potentially powerful tool for characterizing the mechanical properties of diamond films. In this test, pressure was applied on a thin membrane and the out-of-plane deflection of the membrane center was measured. The Young＇s modulus, residual stress, and adhesive strength were simultaneously determined using the load-deflection behavior of a membrane. The free-standing window sample of diamond thin films was fabricated by means of photolithography and anisotropic wet etching. The research indicates that the adhesive strength of diamond thin films is 4.28±0.37 J/m^2. This method uses a simple apparatus, and the fabrication of samples is very easy.

Ultraviolet electroluminescence of diamond thin film

Blue electroluminescence of diamond thin film has already been investigated by some authors. To our knowledge, ultraviolet electroluminescence of diamond thin film has not been reported so far. We have prepared an electroluminescence device with

Preparation of grain size controlled boron-doped diamond thin films and their applications in selective detection of glucose in basic solutions

Boron-doped diamond (BDD) thin films with different crystal grain sizes were prepared by controlling the reacting gas pressure using hot filament chemical vapor deposition (HFCVD).The morphologies and structures of the prepared diamond thin films were characterized by scanning electron microscopy (SEM) and Raman spectroscopy.The electrochemical responses of K4Fe(CN)6 on different BDD electrodes were investigated.The results suggested that electron transfer was faster at the boron-doped nanocrystalline diamond (BDND) thin film electrodes in comparison with that at other BDD thin film electrodes.The prepared BDD thin film electrodes without any modification were used to directly detect glucose in the basic solution.The results showed that the as-prepared BDD thin film electrodes exhibited good selectivity for detecting glucose in the presence of ascorbic acid (AA) and uric acid (UA).The higher sensitivity was observed on the BDND thin film grown on the boron-doped microcrystalline diamond (BDMD) thin film surface,and the linear response range,sensitivity and the low detection limit were 0.25–10 mM,189.1 μA mmol-1 cm-2 and 25 μM (S/N=3) for glucose in the presence of AA and UA,respectively.

VAPOUR PHASE METHOD FOR DIAMOND THIN FILM GROWTH

Diamond has extreme hardness and is a new type of multi-function material which has excellent electrical, optical, thermal and mechanical properties.Russian scientists Derjaguin et al. successfully synthesized diamond on nondiamond substrates by chemical transport reaction method in 1976. In 1982, Japanese sci-

Switching Behaviour of Polycrystalline Diamond Thin Film

Switching phenomena in some semiconductor wafers and thin films were observed early. However, to our knowledge, there is no report about the switching behaviour of diamond thin film. Because the diamond thin film possesses a great number of good properties, such as wide band gap, high breakdown voltage, high electron mobilities and high electron saturation velocity, the investigation on the switching behaviour of diamond thin film will be of great value for achieving high voltage and high power switching devices. We

A Study of Diamond-Like Carbon Thin Films Prepared by Microwave Plasma Chemical Vapour Deposition

In order to deposit good films, we need to study the uniformity of plasma density and the plasma density under different gas pressures and powers. The plasma density was diagnosed by a Langmuir probe. The optical emission spectroscopy （OES） of CH4 and H2 discharge was obtained with raster spectroscopy, with characteristic peaks of H and CH achieved. Diamond-like carbon films were achieved based on the study of plasma density and OES and characterized by atomic force microscope （AFM）, X-ray diffraction instrument （XRD）, Raman spectroscope and profiler.

Effect of Gas Sources on the Deposition of Nano-Crystalline Diamond Films Prepared by Microwave Plasma Enhanced Chemical Vapor Deposition

Nano-crystalline diamond （NCD） films were deposited on silicon substrates by a microwave plasma enhanced chemical vapor deposition （MPCVD） reactor in C2H5OH/H2 and CH4/H2/O2 systems, respectively, with a constant ratio of carbon/hydrogen/oxygen. By means of atomic force microscopy （AFM） and X-ray diffraction （XRD）, it was shown that the NCD films deposited in the C2H5OH/H2 system possesses more uniform surface than that deposited in the CH4/H2/O2 system. Results from micro-Raman spectroscopy revealed that the quality of the NCD films was different even though the plasmas in the two systems contain exactly the same proportion of elements. In order to explain this phenomenon, the bond energy of forming OH groups, energy distraction in plasma and the deposition process of NCD films were studied. The experimental results and discussion indicate that for a same ratio of carbon/hydrogen/oxygen, the C2H5OH/H2 plasma was beneficial to deposit high quality NCD films with smaller average grain size and lower surface roughness.

Preparation of free-standing diamond films for high frequency SAW devices

Free-standing diamond films were prepared by hot filament chemical vapor deposition (HFCVD) method under different conditions. Inter-digital transducers (IDTs) were formed on the nucleation sides of free-standing diamond films by photolithography technique. Then piezoelectric ZnO films were deposited by radio-frequency(RF) reactive magnetron sputtering to obtain the ZnO/diamond film structures. Surface morphologies of the nucleation sides and the IDTs were characterized by means of scanning electron microscopy (SEM), atomic force microscope (AFM) and optical microscopy. The results indicate that the surfaces of nucleation sides are very smooth and the IDTs are of high quality without discontinuity and short circuit phenomenon. Raman spectra show the sharp diamond feature peak at about 1 334 cm?1 and the small amount of non-diamond carbon in the nucleation side. X-ray diffraction (XRD) patterns of the structure of ZnO/diamond films show a strong diffraction peak of ZnO (002), which indicates that as-sputtered ZnO films are highly c-axis oriented.

金刚石薄膜制备及加工技术研究进展

金刚石薄膜具有导热率高、弹性模量大、沉积速度快、化学稳定性好、耐腐蚀等优势,在工业废水处理、生物医学、光学涂层、电子电气、切削刀具等领域应用广泛。文章综述了在低微波功率下衬底的预处理方法、沉积气压、流量比等因素对化学气相沉积制备高质量的金刚石薄膜的影响,介绍了游离磨料研磨过程中驱动方式及工艺参数等对加工后工件的平面度和粗糙度的影响,并探讨了其他多种研磨方式来实现对多晶金刚石片均匀性研磨,为广大学者进一步研究及应用提供参考。

新型纳米金刚石薄膜电极研究综述

文章基于纳米金刚石薄膜电极的电化学领域研究,综述了本课题组的相关工作。内容关注于纳米金刚石薄膜中导电晶粒和晶界对电化学贡献规律,新型纳米金刚石/石墨烯复合薄膜电极的电化学性能研究及在能源催化领域的应用研究等。

AlN陶瓷衬底金刚石薄膜残余应力分析与调控

为系统研究金刚石薄膜残余应力的产生与分布,寻求缓解残余应力的方式,本文首先采用有限元软件ANSYS Workbench对降温过程中金刚石薄膜热应力进行模拟分析,并研究薄膜厚度对热应力的影响,然后利用微波等离子体化学气相沉积法(MPCVD),在氮化铝(AlN)陶瓷衬底上沉积不同厚度的金刚石薄膜,并改变薄膜降温时长和进行退火处理,最后通过SEM、Raman光谱进行表征分析。模拟显示,降温结束后热应力分布并不规律,最大主应力为拉应力,最小主应力为压应力,随着薄膜厚度的增加,最大主应力呈上升趋势,当薄膜厚度为200μm时,最大主应力极大值为373 MPa,接近金刚石薄膜通常断裂强度范围(400~700 MPa),最小主应力和剪切应力随着薄膜厚度的增加呈下降趋势。通过Raman光谱表征得到:金刚石薄膜表面均为残余压应力,随着薄膜厚度和降温时长的增加,残余应力有所下降;经600℃氢气气氛原位退火处理后,薄膜应力畸变有所缓解,金刚石相拉曼峰强度有所提高。

Fabrication and Application of High Quality Diamond-coated Tools

Diamond-coated tools were fabricated using Co-cemented carbide inserts as substrates by the electronically aided hot filament chemical vapor deposition (EACVD). An amount of additive in an acid solution was used to promote the Co etching of the substrate surface. The surface of the WC-Co substrate was decarburized by microwave plasma with Ar-H 2 gas. Effect of the new substrate pretreatment on the adhesion of diamond films was investigated. A boron-doped solution was brushed on the tool surface to diffuse boron into the substrates during diamond deposition. A new process was used to lower the surface roughness of diamond thin films by appropriately controlling deposition parameters. It consists of a composite diamond film chemical vapor deposition procedure including first the deposition of the rough polycrystalline diamond and then the fine-grained diamond. The research results show that the pretreatment including both Co etching in acid solution and Ar-H 2 etching decarburization by microwave plasma is an effective method to enhance adhesive strength. An adequate amount of boron dopant solution can effectively suppress the cobalt diffusion to the surface and avoid the catalytic effect of Co at the high temperature. The composite film CVD process can deposit smooth diamond films with low surface roughness. It is of great significance for improvement of the cutting performances of diamond-coated tools using the above new technology to deposit diamond coatings with the low surface roughness and high adhesive strength on WC-Co substrates.

聚酰亚胺柔性基底红外隔热和保护膜的制备及性能分析

针对聚酰亚胺具有抗高温、易弯折可贴敷、良好的机械延展性和拉伸强度等特性,在125μm厚的柔性聚酰亚胺材料上制备红外隔热和保护膜.在制备过程中,通过对离子源的能量调控可提高柔性基底表面膜层的附着力,根据最小二乘法原理构建薄膜材料光学常数和温度间的关系式,以解决温度变化对薄膜光学性能的影响.在类金刚石薄膜沉积中,采用预热处理法以解决柔性基底变形导致膜厚均匀性较差的问题.红外光谱检测和分析表明,在聚酰亚胺基底上制备的红外隔热薄膜满足使用要求.

Experimental Research of DLC Film Deposited by Filtered Vacuum Arc Evaporation

Diamond like carbon (DLC) films was grown successfully on silicon, titanium and high speed steel (HSS) substrate at low temperature in a filtered vacuum arc deposition system. Arc discharges were established on a graphite cathode in this home built system with a toridal macroparticles filter. Ion current convected by the plasma beam was measured with a negatively biased probe. It was shown that the magnetic field of the coils located on the plasma duct has a strong influence on ion current. Scanning electron microscope (SEM), atomic force microscope (AFM) and Raman spectrum are used to study the DLC films. Tribological behaviors of the deposited film are also studied.

Development of Diamond-Coated Drills

Compared with the sintered polycrystalline diamond, the deposited thin film diamond has the great advantage on the fabrication of cutting tools with complex geometries such as drills. Because of their low costs for fabrication equipment and high performance on high speed machining non-ferrous metals and alloys, metal-compound materials, and hard brittle non-metals, diamond-coated drills find great potentialities in the commercial application. However, the poor adhesion of the diamond film on the substrate becomes the main technical barriers for the successful development and commercialization of diamond-coated tools. In this paper, diamond thin films were deposited on WC-Co based drills by the electron aided hot filament chemical vapor deposition (EACVD). A new multiple chemical pre-treatment technology including microwave oxidation, reaction in alkaline solution and cleaning by ultrasonic treatment in acid solution was developed and affects on the diamond adhesion strength, nucleation and surface morphology were investigated. At the same time, a special setup to fabricate diamond-coated drills was also developed and then the novel CVD process based on the varied parameters controlling model was presented, therefore the uniform quality and homogenized thickness of diamond coating could be available. From practical utilization viewpoint, the cutting performance of the diamond-coated drill was studied by drilling SiC particle reinforced aluminum matrix composite. The satisfied wear resistance and decrease of torque and thrust led to the long life of this kind of drill. This paper exhibited the meaningful work for the development of cutting tools with complex geometries and further extended the application of diamond material.

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.

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。

Optical Properties of Tetrahedral Amorphous Carbon Films and Their Potential for Lab-on-a-Chip

In this study, tetrahedral amorphous carbon (ta-C) films with thicknesses between several 100 nm and several micrometers have been deposited onto polished tungsten carbide and steel substrates by pulsed laser deposition (PLD) using an excimer laser (248 nm wavelength). We investigate the optical properties (e.g. the refractive index (n) and extinction coefficient (k) in the visible and near-infrared wavelength range) of these layers in dependence of the used laser ablation fluence on the target. It is shown that n of ~2000 nm thick ta-C films can be tuned, depending on the sp3-content, between n = 2.5 and 2.8 at a wavelength of 632 nm. Besides of this k reduces with the sp3-content and is as low as 0.03 at sp3-contents of more than 75%. We proof that this gives the opportunity to prepare coating with tailored optical properties. Furthermore, it is shown that the ta-C films have low background fluorescence in the wavelengths range of 380 - 750 nm, which make this thin films attractive for certain optical, medical and biotechnological applications. We present for the first time that one possible application is the use in Lab-on-a-Chip-systems (LOC). Within these systems, the ultrasensitive detection of fluorescence markers and dyes is a challenge. In order to increase the signal-to-noise-ratio, a setup was developed, that used the specific optical properties of ta-C films produced by PLD. We used the ta-C film as an integrated reflector that combined low background fluorescence, a low reflectivity at the excitation wavelength and the high reflectivity at the emission wavelength. We prove that this setup improves the detection of fluorescence photons.

金刚石纳米锥坑阵列结构的制备

采用电感耦合反应离子刻蚀(ICP-RIE)技术刻蚀金刚石薄膜,通过调整刻蚀功率、角度及时间等工艺参数,低成本且高效率地实现了排列整齐的圆形纳米锥坑阵列的可控化制备。对纳米锥坑的制备过程进行深入研究,发现可通过调节刻蚀角度与偏压功率控制氧等离子对金刚石进行高度方向性的刻蚀。荧光检测结果表明,直径为80~120 nm、深度为90~130 nm的纳米锥坑阵列结构可使金刚石薄膜内NV0色心的荧光强度增加21%,SiV-色心的荧光强度增加49%。使用时域有限差分方法对增强原因进行探究,发现纳米锥坑对泵浦激发光有局限作用,并且可在纳米锥坑附近形成法布里-珀罗共振腔,使色心的自发辐射速率加快,进而增加其荧光强度。