金刚石薄膜的制备研究综述

金刚石薄膜具有优异的物理化学性质,在耐磨涂层、生物医学、薄膜微传感器、微机电系统等诸多领域有着广阔的应用前景.文章综述了近年来在金刚石薄膜领域研究的最新进展,着重介绍了目前主流的金刚石薄膜制备方法及优缺点,阐述了薄膜的生长机理以及提高金刚石薄膜沉积速率和质量的技术方法,为该领域的研究人员提供参考.     

PECVD-SiOxNy films for large area self-sustained grids applications

In this work we study the structural properties and mechanical stress of silicon oxynitride (SiO_xN_y) films obtained by plasma enhanced chemical vapor deposition (PECVD) technique at low temperatures (320 °C) and report the feasibility of using this material for the fabrication of large area self-sustained grids. The films were obtained at different deposition conditions, varying the gas flow ratio between the precursor gases (N₂O and SiH₄) and maintaining all the other deposition parameters constant. The films were characterized by ellipsometry, by Fourier transform infrared (FT-IR) spectroscopy and by optically levered laser technique to measure the total mechanical stress. The results demonstrate that for appropriated deposition conditions, it is possible to obtain SiO_xN_y with very low mechanical stress, a necessary condition for the fabrication of mechanically stable thick films (up to 10 μm). Since this material (SiO_xN_y) is very resistant to KOH wet chemical etching it can be utilized to fabricate, by silicon substrate bulk micromachining, very large self-sustained grids and membranes, with areas up to 1 cm² and with thickness in the 2–6 μm range. These results allied with the compatibility of the PECVD SiO_xN_y films deposition with the standard silicon based microelectronic processing technology makes this material promising for micro electro mechanical system (MEMS) fabrication.     

衬底温度对单晶金刚石同质外延生长的 影响规律研究

文章采用微波等离子体化学气相沉积法,以单晶金刚石籽晶为衬底进行金刚石外延生长,通过拉曼光谱、扫描电子显微镜及光学显微镜等多种表征测试手段,系统地研究了衬底温度对单晶金刚石同质外延生长的影响机理.研究结果表明,衬底温度是影响同质外延单晶金刚石生长速率、生长模式和生长缺陷的重要因素:在一定温度范围内,单晶金刚石的生长速率随衬底温度的升高而增加,与此同时,金刚石的生长模式也由丘状生长转变为台阶生长.当单晶金刚石的生长厚度超过1 mm时,较高的衬底温度容易导致沉积层边缘部分产生孪晶等缺陷.拉曼光谱表征结果显示,微波等离子体化学气相法沉积的单晶金刚石质量优于传统的高温高压法.     

Role of the film texturing on the response of particle detectors based on CVD diamond

 Recent improvements in the quality of diamond films grown by Chemical Vapour Deposition (CVD) have made synthetic diamond a very attractive material for detection applications. In this paper, polycrystalline diamond films synthesised by microwave plasma enhanced CVD using a CH₄–CO₂ gas mixture, previously investigated as particle detectors, have been characterised by X-ray diffraction and Raman spectroscopy. The detector response was measured in vacuo under irradiation with 5.5 MeV α-particle from a ²⁴¹Am source. A systematic study of the influence of the film structural properties on the detector performance has been carried out by changing the methane concentration in the growth plasma and the deposition temperature. The existence of a correlation between growth conditions, film texturing and detector performance has been demonstrated. Independently of the substrate temperature, (1 0 0) orientated films exhibit the lowest detection efficiencies. The meas ured collection distances are smaller than the average grain sizes and seem to be limited by trapping centres within the grains. These results are confirmed by Raman analysis. Received: 6 January 1999 / Accepted: 18 January 1999     

A comparative study of the physical properties of CdS, Bi2S3 and composite CdS–Bi2S3 thin films for photosensor application

Thin films of CdS, Bi₂S₃ and composite CdS–Bi₂S₃ have been deposited using modified chemical bath deposition (M-CBD) technique. The various preparative parameters were optimized to obtain good quality thin films. The as-deposited films of CdS, Bi₂S₃ and composite were annealed in Ar gas at 573 K for 1 h. A comparative study was made for as-deposited and annealed CdS, Bi₂S₃ and composite thin films. Annealing showed no change in crystal structure of these as-deposited films. However, an enhancement in grain size was observed by AFM studies. In addition change in band gap with annealing was seen. A study of spectral response, photosensitivity showed that the films can be used as a photosensor.     

Applications of OLEDs that use VUV‐CVD films

Abstract— In photo‐CVD (chemical vapor deposition) in which vacuum‐ultraviolet (VUV) excimer lamps (VUV‐CVD) are used, thin films were deposited at room temperature because VUV photons have the energy to decompose material gases. For the use of OMCTS (octamethylcyclotetrasiloxane), an organic siloxane, we can deposit a self‐flatness film for high‐pressure conditions. The reactants generated by VUV photons have excellent migration characteristics for this condition. Also, the VUV‐CVD film demonstrates low stress, comparatively hard hardness, good electrical properties, and good thermal resistance. The VUV‐CVD film is optimum for planarizing film in the over‐coating deposition step in the production of OLEDs, which requires a low‐temperature process.     

硼掺杂对微波等离子体化学气相沉积制备 金刚石薄膜高择优取向生长的影响

硼(B)掺杂金刚石薄膜因其优异的电化学性能在电化学传感领域获得了广泛的应用.文章采用微波等离子体化学气相沉积法制备硼掺杂金刚石薄膜,通过硼/碳(B/C)比例和工艺参数的调节,成功制备了具备(100)择优取向的金刚石薄膜,分析了B元素影响(100)晶面形成的机理,并进一步探讨了衬底温度、碳源浓度对金刚石薄膜微观形貌的影响.实验发现:B/C比例浓度对金刚石薄膜形貌的影响要大于温度、CH4浓度等其他参数,尤其当B/C=4000 ppm时,形成的四面体形状金刚石颗粒质量最好,晶棱清晰可见,晶面光滑平整;当B/C浓度恒定时,温度与CH4浓度对金刚石薄膜的影响都是通过影响二次形核密度实现的.研究表明,通过适合的硼掺杂比例可以实现高择优取向金刚石薄膜电极的制备.     

Chemical deposition of nanocrystalline nickel oxide from urea containing bath and its use in liquefied petroleum gas sensor

Nanocrystalline nickel oxide (NiO) was deposited onto glass substrates using a chemical deposition method from a bath containing nickel (Ni²⁺) ions and urea at 363 K. The deposition process was based on the reaction between Ni²⁺ and hydroxide ions released from the protolysis of ammonia formed in the decomposition of urea heated at 363 K, which caused to form nickel hydroxide. The structural properties of nickel oxide films were studied by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD analyses showed that nanocrystalline nature remained after heating at 523 K for 2 h. Surface morphology of the nickel oxide film showed worm-like mesoporous structure with pore size in a nanometer range. The chemically deposited nickel oxide films were effectively used as a liquefied petroleum gas (LPG) sensor and the maximum response of 36.5% was recorded on exposure to 0.3 vol% of LPG at 698 K.     

Structural and mechanical properties of polycrystalline silicongermanium for micromachining applications

In this paper, we propose polycrystalline silicon germanium (poly SiGe) as a material suitable for MEMS applications. Films are prepared by chemical vapor deposition (CVD) at atmospheric pressure (AP) or reduced pressure (RP). The structure of the films is investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) for different deposition and annealing conditions. The stress in the as-grown and annealed layers is measured, and the correlation between stress and structural properties is discussed. It is demonstrated that by adjusting the deposition conditions, the stress of the as-grown material can be varied from -145 to 60 MPa. Examples of poly SiGe micromachined devices, prepared at 650°C, are presented. It is shown that by using as-grown poly SiGe, it is possible to realize surface-micromachined suspended membranes having 0.6-μm-wide and 50-μm-long supports. The effect of the average stress and stress gradient on the mechanical stability of surface-micromachined structures is illustrated. Finally, the strain in poly SiGe is measured, and it is found to vary, according to the deposition conditions from -6.88×10^-4 to 3.6×10^-1 These values are compared to those measured for APCVD poly Si     

CVD-diamond-based thermocouple for high sensitive temperature measurements

The possibility to realize a high sensitive thermocouple by means of boron doped chemical vapour deposition (CVD) diamond was investigated. The thermoelectric power of p-type diamond, grown by plasma enhanced CVD was studied for films of electrical resistivity in the 0.2–40 Ω cm range in order to asses the dependence of thermocouple sensitivity on the doping level. The p-type diamond films were prepared by CH₃OH + B₂O₃ vapour addition to a 1% CH₄–H₂ gas mixture during the growth. The conductive films were then tested tracing the I–V characteristic in order to study the conduction properties of the films. An appropriate experimental setup was built to evaluate the thermoelectric properties of the grown samples for different temperatures imposed between two ends of the samples. Firstly, the output voltage was measured maintaining a reference temperature of 273 K at one end and varying the second temperature between 275.5 and 360.5 K. A constant value of the temperature drop of 5 K was then used for an accurate evaluation of the thermoelectric properties of the diamond films for different value of the average temperature. The measurements provided values of thermoelectric power in the range 0.3–0.6 mV/K while conductivity increases. These values showed different decreasing behaviour with increasing temperature for different resistivity of the sample. In particular, more relevant changes in thermoelectric power were measured for high resistive samples.     

Pulsed laser deposition of Y2O3 : Eu thin film phosphors

Thin films of Y₂O₃ : Eu cathodoluminescent (CL) phosphors were deposited using pulsed laser deposition using deposition temperature between 250°C and 800°C, O₂ pressures between residual vacuum (2×10⁻⁵ Torr) and 6 Torr, and post annealing up to 1200° for 1 h in air. The CL efficiency of the best thin film was about one third that of the starting powder. The brightness and efficiency of the thin films improved as the deposition temperature, O₂ pressure and post annealing temperature were increased, except that O₂ pressures above 600 mTorr did not significantly improve the CL properties. At deposition temperatures >600°C, the surface morphology changed from a smooth film to a nodular deposit for O₂ pressures >200 mTorr, with nodule dimensions ≈100 nm. Simultaneously, the CL properties improved dramatically because of enhanced optical scattering out of the thin film. Optical scattering was discussed in terms of anomalous diffraction. The CL properties also improved dramatically with high temperature post annealing. This effect was interpreted in terms of improved crystallinity and activation of the Eu. The low brightness and efficiency of thin films versus powder was affected by depletion of the Eu in the thin films owing to the deposition process.     

BN_xP_(1-x)光电薄膜的性能及在紫外探测中的应用

通过化学气相沉积法在单晶GaAs衬底上成功生长了BNxP1-x薄膜材料。利用扫描电镜观察到该薄膜表面十分光滑,其生长层与衬底之间具有良好的粘合性,不容易脱落。利用紫外-可见光分光光度计(UV)研究了薄膜的紫外吸收特性。并测量出在254nm和365nm波段其量子效率分别为33%和40%,当波长大于400nm时,其量子效率陡然下降。经研究证明:BNxP1-x作为一种宽带隙半导体材料在日盲型紫外探测领域中具有极大的潜能。     

Characterizations of VO2-based uncooled microbolometer linear array

Vanadium dioxide (VO₂) thin films are materials for uncooled microbolometer due to their high temperature coefficient of resistance (TCR) at room temperature. This paper describes the design and fabrication of eight-element uncooled microbolometer linear array using the films and micromachining technology. The characteristics of the array is investigated in the spectral region of 8–12 μm. The fabricated detectors exhibit responsivity of over 10 kV/W, detectivity of approximate 1.94×10⁸ cm Hz^1/2/W, and thermal time constant of 11 ms, at 300 K and at a frequency of 30 Hz. Furthermore, the uncorrected response uniformity of the linear array bolometers is less than 20%.     

NOx sensing properties of In2O3 nanoparticles prepared by metal organic chemical vapor deposition

In₂O₃ nanoparticles were deposited by low-temperature metal organic chemical vapor deposition. The response of 10-nm thick In₂O₃ particle containing layers to NO_x and O₂ gases is investigated. The lowest detectable NO_x concentration is 200 ppb and the sensor performance is strongly dependent on the gas partial pressure as well as on the operating temperature. The sensor response towards 200 ppm of NO_x is found to be above 10⁴. Furthermore, the cross-sensitivity against O₂ is very low, demonstrating that the In₂O₃ nanoparticles are very suitable for the selective NO_x detection.     

CVD参数数据采集系统

在CVD金刚石膜生长过程中,衬底温度、热丝电流、反应室真空度和气源流量等是其重要的工艺参数.针对CVD金刚石膜沉积生长中四个重要的工艺参数,本文设计了数据采集系统.选用片内集成模拟量采集模块的8098单片机为下位机,上位机采用工控机,通过RS232串口进行通信.该主从式数据采集系统,硬件配置简单,抗干扰能力强,软件编程方便,人机界面友好.该系统已通过调试,运行良好.     

面向化学气相沉积生长单晶金刚石的高导热嵌入型 基片托盘设计及其高质量生长工艺研究

针对高功率密度微波等离子体化学气相沉积法生长单晶金刚石过程中,金刚石籽晶表面温度容易发生漂移的问题,提出了一种新的基片托盘结构设计方法.基片托盘中间采用通孔结构,以避免籽晶底部与钼托盘的直接接触,在基片托盘与水冷台之间、籽晶和水冷台之间添加高导热材料氮化铝片,以保证外延沉积金刚石所需的均匀温度场环境.实验结果显示,利用新型基片托盘可以连续工作48 h,并获得生长厚度达1.66 mm的单晶金刚石,经过多次反复生长可实现厚度3 mm的高质量单晶金刚石制备.新型基片托盘能有效地抑制生长过程中石墨等大颗粒煤烟沉积引起的温度漂移现象,满足不同条件下金刚石单晶的同质外延生长,抑制籽晶边沿处多晶金刚石的生成,从而保证金刚石单晶在高功率密度下长时间稳定生长,获得高质量、大尺寸的化学气相沉积单晶金刚石.     

Electric and ferroelectric properties of PZT/SBT multilayer films prepared by photochemical metal-organic deposition

The electric and ferroelectric properties of lead zirconate titanate and strontium bismuth tantalate multilayer films prepared using photosensitive starting precursors were characterized. The electric and ferroelectric properties were investigated by characterization of the effect of stacking order of four ferroelectric layers of PZT or SBT in the multilayer films of 4-PZT, PZT/2-SBT/PZT, SBT/2-PZT/SBT, and 4-SBT. The P_r value of the 4-SBT multilayer film was relatively small (6 μC/cm²) and a two times higher value (12 μC/cm²) was obtained with the SBT/2-PZT/SBT multilayer film. The films with SBT layers at the top and bottom showed improved leakage current and fatigue resistance compared to the films with PZT layers at the top and bottom. It was revealed that the defect dipole was reduced at the SBT/Pt interface due to a self-regulation layer such as (Bi₂O₂)²⁺ in the SBT film. Also, the bottom layer on the Pt substrate showed a significant influence on the growth orientation of the entire ferroelectric films.     

Manufacture and characterization of sol–gel V1−x−yWxSiyO2 films for uncooled thermal detectors

V_1−x−yW_xSi_yO₂ films for uncooled thermal detectors were coated on sodium-free glass slides with sol–gel process, followed by the calcination under a reducing atmosphere (Ar/H₂ 5%). The V_1−x−yW_xSi_yO₂ films as prepared inherit various phase transition temperatures ranging from 20 to 70 °C depending on the dopant concentrations and the fabrication conditions. Compared to the hysteresis loop of plain VO₂ films, a rather steep loop was obtained with the addition of tungsten components, while a relaxed hysteresis loop with the tight bandwidth was contributed by Si dopants. Furthermore, the films with switching temperature close to room temperature were fabricated to one-element bolometers to characterize their figures of merit. Results showed that the V_0.905W_0.02Si_0.075O₂ film presented a satisfactory responsivity of 2600 V/W and detectivity of 9 × 10⁶ cm  Hz^1/2/W with chopper frequencies ranging from 30 to 60 Hz at room temperature. It was proposed that with appropriate amount of silicon and tungsten dopants mixed in the VO₂, the film would characterize both a relaxed hysteresis loop and a fair TCR value, which effectively reduced the magnitude of noise equivalent power without compromising its performance in detectivity and responsivity.     

施加偏压对采用等离子体辅助热丝化学气相沉积法在硬质合金上沉积金刚石/ 碳化硅/ 硅化钴复合薄膜的影响

金刚石涂层硬质合金是一种出众的刀具材料,将碳化硅掺入金刚石涂层中不仅可以提高涂层的断裂韧性,还能够提高薄膜与基体之间的粘附性。文章采用氢气、甲烷和四甲基硅烷混合气体作为反应气体,用直流等离子体辅助热丝化学气相沉积法在硬质合金基体上沉积金刚石-碳化硅-硅化钴复合薄膜。通过扫描电子显微镜、电子探针显微分析、X 射线衍射和拉曼光谱对薄膜的表面形貌、成分以及结构进行了分析,结果显示此复合薄膜中含有金刚石、碳化硅(β-SiC)和硅化钴(Co2Si、CoSi)。复合薄膜的结构和成分可通过调节偏流和气相中四甲基硅烷的浓度来控制,随着偏流的增加,复合薄膜中金刚石晶粒尺寸变大且含量增加,β-SiC 的含量减少,因为复合薄膜沉积过程中正偏压促进金刚石的生长,并且增强金刚石的二次形核。虽然电子轰击同时增强了氢气、甲烷和四甲基硅烷的分解,但随着偏流的增加,气相中产生的碳源浓度高于硅源浓度,使金刚石比β-SiC 在空间生长上更具有优势。当偏流过高时则形成纯金刚石,不能够同时沉积金刚石、β-SiC 和硅化钴三种物质。通过调节偏压和气体成分,金刚石和碳化硅在复合薄膜中的分布得以控制。该工作有助于理解和控制复合材料和超硬薄膜的生长,所产生的复合薄膜可用于提高金刚石涂层刀具切削性能。     

Uniform carbon‐nanotube emitter for field‐emission displays

Abstract— The synthesis of carbon‐nanotube (CNT) field emitters for FEDs by thermal chemical vapor deposition (CVD) and their structural and emission characterization are described. Multi‐walled nanotubes (MWNTs) were grown on patterned metal‐base electrodes by thermal CVD, and the grown CNTs formed a network structured layer covering the surfaces of the metal electrode uniformly, which realized uniform distribution of electron emission. A technique for growing narrow MWNTs was also developed in order to reduce the driving voltage. The diameter of MWNT depends on the growth temperature, and it has changed from 40 nm at the low temperature (675°C) to 10–15 nm at the high temperature (900–1000°C). Moreover, narrower MWNTs were grown by using the metal‐base electrode covered with a thin alumina layer and a metal catalyst layer. Double‐walled nanotubes (DWNTs) were also observed among narrow MWNTs. The emission from the narrow CNTs showed a low turn‐on electric field of 1.5 V/μm at the as‐grown layer.