Laser Processing of Diamond and Boron Nitride Epitaxial Layers

这项研究得到了国家科学基金材料加工联合倡议的资助。该研究项目的目标是利用激光诱导光解和热解方法研究金刚石和氮化硼薄膜的外延生长。这种薄膜在室温和大气压下是亚稳定的，因此需要非平衡方法来生长它们。脉冲激光辐照在局部引入加热和瞬变原子激发，形成亚稳态相。这种材料将在氧化镁和碳化硅上外延生长，在硅衬底上有几组与薄膜相匹配的主要晶面。在原位激光化学气相沉积过程中，通过在生长腔中引入掺杂气体，对金刚石薄膜进行掺杂。研究的重点将放在外延生长的基本方面，包括分析缺陷的形成，以及弹性应变和界面应力分布的影响。薄膜将使用高分辨率和分析性的透射电子显微镜、卢瑟福背散射光谱、二次离子质谱仪、扫描俄歇电子光谱、电子光谱化学分析以及拉曼和红外光谱技术来表征化学成分和成键特性。其中一些薄膜将进行机械和电学性能评估。钻石和氮化硼是人类已知的所有材料中最硬的，在切割工具和耐磨涂层等应用中很有用。钻石的其他有用特性包括高介电强度、化学惰性、光学透明性、大带隙、高电阻率和高导热系数。这些特性使该材料有可能用于在高温和高辐射环境下运行的半导体器件。

This research supported by the National Science Foundation under the Materials Processing Joint Initiative. The objective of the research program is to study the epitaxial growth of thin film diamond and boron nitride using laser-induced photolytic and pyrolytic methods. The thin films are metastable at room temperature and atmospheric pressure, thereby requiring non- equilibrium methods to grow them. Pulsed laser irradiation introduces heating and transient atomic excitations locally to form the metastable phases. The materials will be grown epitaxially on magnesium oxide and silicon carbide on silicon substrates, where there are sets of major lattice planes which match those of the thin films. The diamond films will be doped during in-situ laser chemical vapor deposition by introducing dopant gases into the growth chamber. The emphasis in the research will be on the fundamental aspects of epitaxial growth, to include analysis of the formation of defects, and the effects of distribution of elastic strains and interfacial stresses. The thin films will be characterized using high-resolution and analytical transmission electron microscopy, Rutherford Backscattering Spectroscopy, Secondary Ion Mass Spectroscopy, Scanning Auger Electron Spectroscopy, Electron Spectroscopic Chemical Analysis, and Raman and infrared spectroscopy techniques will be used to characterize the chemical composition and the bonding characteristics. Some of the films will be evaluated for mechanical and electrical properties. Diamond and boron nitride are the hardest of all materials known to man, and are useful in applications such as cutting tools and wear resistant coatings. Other useful properties of diamond include high dielectric strength, chemical inertness, optical transparency, large band gap, high electrical resistivity, and high thermal conductivity. These properties make the material potentially useful for semiconductor devices for operation in high temperature and high radiation environments.