金刚石自支撑膜的高温红外透过性能

由于金刚石具有低吸收和优异的力学与导热性能使其成为长波(8~12μm)红外光学窗口材料的重要选择。对于许多极端条件的应用,化学气相沉积(CVD)金刚石自支撑膜的高温光学性质至关重要。应用直流电弧等离子喷射法制备光学级金刚石自支撑膜进行变化温度的红外光学透过性能研究,采用光学显微镜、X射线衍射、激光拉曼和傅里叶变换红外-拉曼光谱仪检测CVD金刚石膜的表面形貌、结构特征和红外光学性能。结果表明:在27℃时金刚石膜长波红外8~12μm之间的平均透过率达到65.95%,在500℃时8~12μm处的平均透过率为52.5%。透过率下降可分为3个阶段。对应于透过率随温度的下降,金刚石膜的吸收系数随温度的升高而增加。金刚石自支撑膜表面状态的变化,对金刚石膜光学性能的影响显著大于内部结构的影响。     

CVD金刚石的高温氧化及其保护

化学气相沉积(CVD)金刚石具有优异的机械、光学和热学性能,成为高速长波红外窗口的首选材料,但是当高速飞行时,由于空气动力加热会产生很高的温度而使其迅速遭受氧化,甚至完全失效.简要概述了CVD金刚石高温氧化现象及机理、抗氧化保护的最新研究进展.     

金刚石-硫化锌复合窗口的弹性应变研究

对于金刚石－硫化锌复合红外光学窗口，结构中存在的热应力和挠曲度的大小对其可靠性有很大的影响。利用弹性应变模型研究了在光学焊接中不同粘接温度和金刚石厚度下金刚石－硫化锌复合窗口将发生的最大应力、曲率和衬底到边缘的挠曲率。计算结果表明，当膜厚在极值附近时，复合结构明显弯曲、ZnS表面的应力极大；如何粘接温度较高，复合结构将严重变形，ZnS中所受的应力可能会超过其自身的断裂强度。当对金刚石－硫化锌复合红外窗口设计时，了解结构中存在的热应力和挠曲度的大小是很有用的。     

工艺条件对金刚石膜红外透射率影响的研究

为了优化金刚石沉积工艺,制备高透射率的CVD金刚石薄膜,采用傅里叶红外光谱仪对不同工艺条件下制备的CVD金刚石膜的红外透射率进行了测量,分析了不同工艺条件对金刚石膜红外透射率的影响,获得了最佳沉积参数.结果表明,金刚石膜的红外透射率与工艺条件密切相关,当衬底温度为750℃,碳源体积分数为2%,压强为2.5kPa时沉积的金刚石膜红外透射率最佳.     

红外光学材料硫化锌衬底上沉积金刚石膜的研究

采用微波等离子体化学气相沉积法,在预镀陶瓷过渡层的硫化锌衬底上沉积金刚石膜。在以前的实验中,我们发现在陶瓷过渡层上沉积金刚石膜极其困难,但采用金刚石诱导形核方法后,我们已经在过渡层／硫化锌试样表面获得了很小面积（约1mm宽的环状区域）的金刚石形核。本文对前期的诱导形核工作进行了一定改进,目前已经使形核生长范围大大增加,沉积面积超过原来10倍。此外,本文对金刚石／过渡层／硫化锌试样的红外透过特性以及金刚石膜质量等进行了评价。     

金刚石膜红外光学性质的研究

采用热灯丝化学气相沉积(CVD)方法,通过独特的衬底表面预处理工艺及控制沉积参数,制备出了晶粒细、表面光滑的单片金刚石膜样品。采用SEM观察了样品生长面的表面形貌,通过激光Raman对样品进行了金刚石结构的确认。在450～4000cm~(-1)范围测试了金刚石膜样品的红外光学透过谱,通过分析认为:平均透过率随波长减小而衰减主要是由于金刚石膜生长面的表面粗糙度引起光谱散射造成的。     

CVD金刚石膜高效超精密抛光技术

CVD金刚石膜作为光学透射窗口和新一代计算机芯片的材料,其表面必须得到高质量抛光,但是现存方法难以满足既高效又超精密的加工要求.本文提出机械抛光与化学机械抛光相结合的方法.首先,采用固结金刚石磨料抛光盘和游离金刚石磨料两种机械抛光方法对CVD金刚石膜进行粗加工,然后采用化学机械抛光的方法对CVD金刚石膜进行精加工.结果表明,采用游离磨料抛光时材料去除率远比固结磨料高,表面粗糙度最低达到42.2 nm.化学机械抛光方法在CVD金刚石膜的超精密抛光中表现出较大的优势,CVD金刚石膜的表面粗糙度为4.551 nm.     

用压痕试验法研究CVD金刚石膜的粘附性能

在观察与分析压入过程中CVD金刚石膜开裂方式的基础上,初步探讨了用压痕试验法评定CVD金刚石膜粘附性能的可行性．采用反映膜／基粘附性能的临界开裂或剥落载荷P_er和抗裂性参数dP／dX两指标评定了硬质合金基体表面经不同预处理方法和沉积工艺参数合成的金刚石膜的粘附性能;研究了粘附性能指标与沉积工艺参数（如甲烷浓度、沉积气压、沉积功率）之间的关系．适当的表面预处理、适中的甲烷浓度、较低的沉积气压、较高的沉积功率均有利于改善金刚石膜的粘附性能．     

金刚石膜辐射探测器的研究进展

阐述了金刚石作为激发材料在辐射探测器中的应用范围,比较了硅、化学气相沉积(CVD)金刚石膜和天然金刚石作为探测器用激发材料的性能优劣,介绍了CVD金刚石膜辐射探测器的原理和结构,综述了金刚石辐射探测器的国内外研究进展,展望了CVD金刚石膜辐射探测器的应用前景.     

CVD金刚石膜的场发射机制

利用热灯丝化学气相沉积方法在光滑的钼上沉积了金刚石膜,用扫描电子显微镜和Raman谱对金刚石膜进行了分析。结果表明金刚石膜是由许多金刚石晶粒组成,晶粒间界主要是石墨相,并且在膜内有许多缺陷。金刚石膜的场发射结果表明高浓度CH4形成的金刚石膜场发射阈位电场较低浓度CH4形成的金刚石为低。这意味着杂质（如石墨）和缺陷（悬挂键）极大地影响了膜的场发射性能。根据以上结果,提出了一种CVD金刚石膜的场发射机制即膜内的缺陷增强膜内的电场,石墨增大电子的隧穿系数以增强CVD金刚石膜的场发射。     

Effect of carbon concentration on the optical properties of nanocrystalline diamond films deposited by hot-filament chemical vapor deposition method

With reducing diamond grain size to nano-grade, the increase of grain boundaries and non-diamond phase will result in the change of the optical properties of chemical vapor deposition (CVD) diamond films. In this paper, the structure, morphology and optical properties of nanocrystalline diamond (NCD) films, deposited by hot-filament chemical vapor deposition (HFCVD) method under different carbon concentration, are investigated by SEM, Raman scattering spectroscopy, as well as optical transmission spectra and spectroscopic ellipsometry. With increasing the carbon concentration during the film deposition, the diamond grain size is reduced and thus a smooth diamond film can be obtained. According to the data on the absorption coefficient in the wavelength range from 200 to 1100 nm, the optical gap of the NCD films decreases from 4.3 eV to 3.2 eV with increasing the carbon concentration from 2.0% to 3.0%. From the fitting results on the spectroscopic ellipsometric data with a four-layer model in the photon energy range of 0.75-1.5 eV, we can find the diamond film has a lower refractive index (n) and a higher extinction coefficient (k) when the carbon concentration increases.     

ZnS窗口上过渡层的研究

研究采用ＡｌＮ为过渡层在ＺｎＳ红外光学窗口材料上进行金刚石膜保护。还对膜进行结构分析和光学测试。     

生长温度对CVD金刚石薄膜的影响

系统研究了ＣＶＤ金刚石薄膜成膜过程中生长温度对薄膜质量、生长率和力学性能的影响。研究结果表明：在典型沉积条件下，生长温度愈高、薄膜的晶体质量愈好；但薄膜的应力状况和附着性能变坏；在８００℃时，金刚石薄膜的生长速率最大。讨论了ＣＶＤ金刚石薄膜作为机械工具涂层的最佳生长温度。     

The versatility of hot-filament activated chemical vapor deposition

In the field of activated chemical vapor deposition (CVD) of polycrystalline diamond films, hot-filament activation (HF-CVD) is widely used for applications where large deposition areas are needed or three-dimensional substrates have to be coated. We have developed processes for the deposition of conductive, boron-doped diamond films as well as for tribological crystalline diamond coatings on deposition areas up to 50 cm × 100 cm. Such multi-filament processes are used to produce diamond electrodes for advanced electrochemical processes or large batches of diamond-coated tools and parts, respectively. These processes demonstrate the high degree of uniformity and reproducibility of hot-filament CVD. The usability of hot-filament CVD for diamond deposition on three-dimensional substrates is well known for CVD diamond shaft tools. We also develop interior diamond coatings for drawing dies, nozzles, and thread guides.Hot-filament CVD also enables the deposition of diamond film modifications with tailored properties. In order to adjust the surface topography to specific applications, we apply processes for smooth, fine-grained or textured diamond films for cutting tools and tribological applications. Rough diamond is employed for grinding applications. Multilayers of fine-grained and coarse-grained diamond have been developed, showing increased shock resistance due to reduced crack propagation.Hot-filament CVD is also used for in situ deposition of carbide coatings and diamond-carbide composites, and the deposition of non-diamond, silicon-based films. These coatings are suitable as diffusion barriers and are also applied for adhesion and stress engineering and for semiconductor applications, respectively.     

Investigation into polishing process of CVD diamond films

A new technique used for polishing chemical vapor deposition (CVD) diamond films has been investigated, by which rough polishing of the CVD diamond films can be achieved efficiently. A CVD diamond film is coated with a thin layer of electrically conductive material in advance, and then electro-discharge machining (EDM) is used to machine the coated surface. As a result, peaks on the surface of the diamond film are removed rapidly. During machining, graphitization of diamond enables the EDM process to continue. The single pulse discharge shows that the material of the coated layer evidently affects removal behavior of the CVD diamond films. Compared with the machining of ordinary metal materials, the process of EDM CVD diamond films possesses a quite different characteristic. The removal mechanism of the CVD diamond films is discussed.     

Optimization of chemical vapor deposition diamond films growth on steel: correlation between mechanical properties, structure, and composition

In the present work we perform optimization of mechanical and crystalline properties of CVD microcrystalline diamond films grown on steel substrates. A chromium-nitride (Cr-N) interlayer had been previously proposed to serve as a buffer for carbon and iron inter-diffusion and as a matching layer for the widely differing expansion coefficients of diamond and steel. However, adhesion and wear as well as crystalline perfection of diamond films are strongly affected by conditions of both Cr-N interlayer preparation and CVD diamond deposition. In this work we assess the effects of two parameters. The first one is the temperature of the Cr-N interlayer preparation: temperatures in the range of 500 degrees C-800 degrees C were used. The second one is diamond film thickness in the 0.5 microm-2 microm range monitored through variation of the deposition time from approximately 30 min to 2 hours. The mechanical properties of so deposited diamond films were investigated. For this purpose, scratch tests were performed at different indentation loads. The friction coefficient and wear loss were assessed. The mechanical and tribological properties were related to structure, composition, and crystalline perfection of diamond films which were extensively analyzed using different microscopic and spectroscopic techniques. It was found that relatively thick diamond film deposited on the Cr-N interlayer prepared at the temperature similar to that of the CVD process has the best mechanical and adhesion strength. This film was stable without visible cracks around the wear track during all scratch tests with different indentation loads. In other cases, cracking and delamination of the films took place at low to moderate indentation loads.     

温度对化学水浴法制备ZnS薄膜的影响

采用化学水浴法在玻璃上制备了太阳能电池中的ZnS缓冲层。采用SEM、EDS、XRD和nkd-分光光度计等手段研究了水浴温度对ZnS薄膜的表面形貌、结构和光学性能的影响。结果表明,升高温度不能明显改变薄膜的结晶性、形貌和沉积生长方式,能否成膜与温度的关系也不大,但成膜速率对温度的依赖性较大。随温度的升高,薄膜的透过率先减小后增大,反射率则先增大后减小。对同一试样而言,透过率和反射率对应较好。当温度为70℃时,可制得禁带宽度为3.83eV、符合化学计量比、平整的非晶ZnS薄膜。     

A comparative study of p-type diamond films using Raman and transport measurements

The influence of deposition temperature in the properties of synthetic diamond films grown by two different chemical vapor deposition (CVD) techniques, hot-filament- and microwave-plasma-assisted, was investigated. These samples were obtained using the optimal growth conditions previously achieved in this work. Raman spectroscopy was employed in order to investigate the diamond film quality as a function of the deposition temperature. It was found that the nondiamond carbon bands decrease as the deposition temperature increases for both the deposition methods, leading to higher-quality diamond films. The micro- and macro-Raman spectra showed that the nondiamond band is already present in a single diamond grain. Both techniques provided well homogeneous diamond films and with equivalently good quality. Boron-doped diamond films with different carrier concentration levels were also studied. In order to get details about the electrical properties of the films, resistivity as a function of the boron concentration—in association with Raman spectra—and temperature-dependent transport measurements were employed. The results showed that the boron doping is the main responsible for the conductivity and that the variable range hopping (VRH) mechanism dominates the transport in these doped diamond films.     

Deposition of Diamond Films in a Closed Hot Filament CVD System

A closed system hot filament chemical vapor deposition (CVD) reactor has been used to deposit diamond films on silicon substrates. A fixed charge of hydrogen gas is fed into the deposition system until the desired deposition pressure level is reached. A solid graphite cylindrical rod held above the tungsten filament was the carbon source. System parameters for diamond film growth have been determined. The diamond structure of the films has been verified by x-ray diffraction (XRD). Morphology typical of CVD diamond films has been observed in scanning electron microscopy (SEM). The quality of the diamond films has been evaluated by micro-Raman spectroscopy.