【作者】 沈沪江；

【导师】 夏义本； 王林军；

【作者基本信息】 上海大学 ， 材料学， 2010， 博士

【摘要】 金刚石薄膜以其优异的电、光、热和机械性能及高的抗辐照能力和物理化学稳定性等在微电子和光学领域得到了极大重视。纳米金刚石以其更光滑的表面、更低的摩擦系数和更优异的场发射性能,已成为金刚石薄膜研究领域的新热点。本文研究了纳米金刚石薄膜的沉积工艺和性能,研究了纳米金刚石薄膜辐射探测器的制备工艺及其探测性能,同时还分别研究了作为X射线掩膜材料和在强磁场条件下的纳米金刚石薄膜的生长工艺,以探索纳米金刚石薄膜在各种不同领域内的应用。首先采用热丝化学气相沉积法制备了纳米金刚石薄膜,表征了形貌结构和光学性能,确定了最佳生长参数,获得样品表面晶粒尺寸约为30nm,厚度为1000nm,近红外透过率大于50%。提出了一种快速生长高质量厚纳米金刚石膜的方法:先用高温生长,再用低温生长,以克服高温生长引起的孔洞问题。其次研究了纳米金刚石薄膜辐射探测器的制备工艺和探测性能。使用ANSYS软件对电极宽度不同的纳米金刚石薄膜辐射探测器的电场分布进行模拟,确定了电极的尺寸参数。设计制作了光刻掩膜版,通过光刻和直流溅射工艺制备出纳米金刚石薄膜辐射探测器。研究了晶粒尺寸为20nm～150nm、粗糙度为22nm～45nm的纳米金刚石薄膜制备的光导型探测器在X射线辐照下的电学性能和光谱响应。电流—电压测试表明,随着金刚石晶粒的减小,薄膜电阻率下降,在5.9 keV 55Fe X射线辐照下,大晶粒(150nm)纳米金刚石薄膜探测器的光电流(Iph)与暗电流(Id)的比值Iph/Id几乎是小晶粒(20nm)探测器的4倍。X射线辐照下的脉冲高度光谱测量表明,大晶粒探测器的计数率和能量分辨率优于小晶粒探测器。这些结果说明:大晶粒金刚石薄膜探测器具有高的信噪比和电荷收集效率,适合于核辐射探测器的制备。随后采用氢刻蚀的方法探索了可作为X射线掩膜材料的纳米金刚石薄膜的生长工艺。对薄膜样品的显微结构、光学和电学性能的表征和分析发现:在其他沉积参数保持一定的情况下,随着氢刻蚀时间的增加,晶粒尺寸逐步减小,薄膜的表面平整度、折射率以及光学透过率明显提高,薄膜的暗电流和损耗减小,介电常数接近天然金刚石。采用同步辐射装置,测试和研究了纳米金刚石薄膜在软X射线波段的透过率。经过氢刻蚀的薄膜,X射线透过率在258eV处达到52.8%,明显高于未经刻蚀的薄膜(24.8%),符合X射线光刻掩模材料的要求。最后研究了强磁场下纳米金刚石的沉积工艺。研究了不同磁场强度(0-5T)对纳米金刚石性能的影响,结果表明:随磁场强度的增强,薄膜晶粒有逐渐细化的趋势。探索了强磁场下纳米金刚石沉积原理。更多还原

【Abstract】 Diamond film is a kind of competitive material with its outstanding electrical, optical, thermal and mechanical properties as well as high anti-radioactive intensity and high physical and chemical stability. Compared with micro-crystalline diamond, Nano-Crystalline Diamond(NCD) is with more slippery surface, lower friction factor and better performance in field ejection, so that, it becomes the new hotpot in the research of diamond films. This essay focuses on the CVD NCD film. The fabrication and properties of NCD films are studied together with that of NCD film radiation detector. H etched NCD fims are studied to see if they can be used as X ray masks. At the same time, NCD films are successfully fabricated under high magnetic field to broaden their applications.First, NCD films are prepared by Hot Filament Chemical Vapor Deposition (HFCVD), while their surface morphology, optical and detective performances are studied in depth. The best growth parameters are got with the samples’grain size being about 30nm, thickness being 1000nm and near infrared transmittance over 50%. An innovative method is proposed hereof for the growth of thick NCD film in a fast way, where a high growth temperature is introduced in initial stage.Next, NCD film radiation detector is successfully fabricated by photolithography and sputtering. ANSYS ( a software based on finite-element method) is used to simulate the distribution of the electric field of the NCD film radiation detectors. The geometric configuration of interdigital electrodes is determined to be 25nm in width and 50nm for pitch. A special photo mask is designed and made for the photolithography. The electrical performance and spectral response of the MSM photo-conductive NCD detectors are studied with the samples’grain size vary from 20nm to 150nm and roughness from 22nm to 45nm. I-V test results show that with the decrease of the grain size, the resistivity of diamond film decreases and the ratio of the photocurrent to the dark-current (Iph/Id) of the detectors decreases rapidly from 0.45 to 0.099 under the radiation of 5.9 keV 55Fe X-ray. At an electric field of 50 kV/cm, the energy resolution of detectors with large grains (150 nm) is 17.5%, for those with small grains (20 nm), the number is 22.7%. All the test results show that larger grain samples are with better counting rate, higher SNR and charge collection efficiency, and therefore, they are more appropriate for nuclear radiation detectors.Then, Hydrogen etching method is applied to the experiments to optimize the NCD film deposition process. From the test of micro-structure, optical and electrical properties, it shows that, with certain deposit parameters, the increase of etching time will lead to the decrease of the grain size and of surface roughness, the increase of the refractive index and optical transmission rate and the diminish of NCD film’s dark current and dielectric loss, while their dielectric constant come closer to that of natural diamond. NCD films are also tested for soft X-ray transmission by synchrotron radiation. It can obviously be seen that hydrogen-etched NCD films do much better in X-ray transmission: the transmission reaches 52.8% at an X-ray photon energy of 258eV, while the number for non-etched NCD is only 24.8%. The etched NCD film has met the requirements for X-ray mask materials.Finally, the deposition of NCD films in high magnetic field is researched. The influence of different magnetic field intensity (0-5T) on the performance of NCD films is studied. With the increase of magnetic intensity, the grain size of NCD films decreases. The principle of nano-crystalline diamond film deposition in high magnetic field is also studied.更多还原