【作者】 高凯；

【导师】 李志宏；

【作者基本信息】 天津大学 ， 材料学， 2012， 博士

【摘要】 金刚石作为宽禁带半导体材料与其它材料相比,具有非常低的介电常数,很高的禁带宽度和极高的热导率及优良的光学性质。金刚石基多晶材料潜在应用亟待研究和开发,例如作为陶瓷基板、热沉材料、微波窗口材料等。本文分别采用高温高压法、溶胶-凝胶低温常压烧结法和固相反应低温常压烧结法制备了金刚石多晶材料,通过扫描电子显微镜、荧光光谱仪、阻抗分析仪等研究了其微观形貌、电学、热学和光学等性质,并探讨了不同烧结方法对这些多晶材料的性能影响。研究结果表明:高温高压快速烧结法制备的金刚石多晶材料,其具有近紫外发光特性。添加不同的过渡金属时,发现在低于Co共晶点温度时,具有低熔点高沸点的金属Zn元素以及Si和Zn的混合添加剂能够促进金刚石的烧结和致密化,并且能够抑制金刚石的石墨化。对所得到的含Zn金刚石多晶材料进行光致发光光谱的测试,发现当激发波长为200nm时,PL光谱在紫外310到390nm的范围内发现了一系列的尖锐的荧光谱,其发射线半高宽小于0.5nm。而此条件下烧结制备的含Si金刚石复合多晶材料具有较高的电阻率和高电压下的电阻稳定性;溶胶-凝胶低温常压烧结法制备的金刚石多晶材料电阻率比金刚石薄膜电阻率略大,但介电损耗更小。以柠檬酸为络合剂,利用溶胶凝胶法制备的金刚石多晶材料,其介电常数降低到2.55,介电损耗降低到10-3,具有很好的高频介电稳定性;与溶胶凝胶法相比,固相反应法制备的金刚石多晶材料烧结温度较高,气孔率较大,多晶复合材料的介电常数与介电损耗也偏大。更多还原

【Abstract】 Diamond has many advantages compared with other semiconductor materials, such as low dielectric constant, high band gap, good electron hole mobility, high thermal conductivity and optical properties. The potential use of polycrystalline diamond as ceramic substrate, heat sink materials, and microwave window materials needs an urgent research and development. In this paper, polycrystalline diamond was prepared by the high-temperature and high-pressure method, pressureless sintering of sol-gel and solid state reaction method, respectively. The microstructure and electrical, thermal, optical and other properties and the effects of different sintering method had been investigated by SEM, PL spectroscopy and impedance analyzer.The main findings of this paper were as follows: the near ultraviolet light-emitting properties of polycrystalline diamond materials prepared by high-temperature and high-pressure and rapid sintering. It had been shown that the metal element Zn with high boiling and low melting point could promote the sintering and densification of diamond below the Co eutectic temperature by different phases of transition metals addition. Zn-containing polycrystalline diamond material photoluminescence spectra was investigated, it had been found that a series of sharp fluorescence spectra with the emission line width at half maximum was less than 0.5 nm when the excitation wavelength was 200nm and PL spectra was in the UV range of 310 to 390nm. The Si-containing polycrystalline diamond composite material had high resistivity and high volage resistance stability under this condition. The diamond composite material prepared by sol-gel and low-temperature pressureless sintering method had a slightly larger resistance and smaller dielectric loss than thin diamond film. The dielectric constant and the dielectric loss of diamond/ceramic polycrystalline composites materials with good high-frequency dielectric stability prepared by citric acid as complexing agent reduced to 2.55 and 10-3, respectively. Compared with the polycrystalline diamond prepared by sol-gel method, the polycrystalline diamond prepared by solid-phase reaction and high temperature sintering needed high sintering temperature and it had larger porosity, dielectric constant and dielectric loss.更多还原