Low Density Supersonic Plasma Jet Synthesis of Thin Films of Refractory and Wide Band-Gap Nitrides

摘要- Cappelli CTS-9707923 这是一个结合实验和模拟研究为导向 致力于氮化物族中先进材料的有效合成工艺。 由电弧加热流产生并膨胀到低密度的超音速等离子体射流提供了大通量的高能解离（原子）氮，各种各样的反应物（例如镓氮化物、铝氮化物、甲烷或硼氮化物）被注入其中以产生反应流，产物从该反应流沉淀到衬底上以形成膜、涂层或外延层。 向衬底施加受控电偏压的能力提供了影响膜结构和性质的附加变量。 该项目包括模拟反应物注入和随后在羽流中的分解;模拟离子通过衬底周围的等离子体鞘层的传输;开发薄膜生长的经验非均匀模型;用光学吸收光谱法测量薄膜沉积过程中临界气相物质的浓度;用分子束质谱法测量更广泛的中性和离子自由基的浓度和能量;以及通过红外吸收（IR）光谱、拉曼光谱、X射线光电子能谱（XPS）、X射线衍射（XRD）和近边X射线吸收精细结构光谱（NEXAFS）。 还测量了沉积膜的光学和机械性能。 这项研究解决了一些氮化物的合成，形成了“太空时代”陶瓷的基础。 这些包括立方氮化硼（c-BN）、氮化碳（C3 N4）、氮化镓（GaN）、氮化铝（AlN）和混合的铝/氮化镓。 这些材料不寻常的机械、电学和光学性质使它们在许多应用中具有吸引力，但由于缺乏经济的合成方法，它们的广泛应用受到抑制。

Abstract - Cappelli CTS-9707923 This is a combined experimental and modelling study oriented toward an efficient process for the synthesis of advanced materials in the nitride family. A supersonic plasma jet generated by an arc-heated flow and expanded to low densities provides a large flux of energetic dissociated (atomic) nitrogen into which a wide variety of reactants (such as gallium trichloride, aluminum trichloride, methane, or boron trichloride) are injected to generate a reacting flow from which products condence onto a substrate to form films, coatings, or epitaxial layers. The ability to apply a controlled electrical bias to the substrate provides an added variable to influence film structure and properties. The project includes modelling of reactant injection and subsequent decomposition in the plume; modelling of ion transport through the plasma sheath surrounding the substrate; development of empirical heterogeneous models of film growth; measurement of concentratures of critical gas-phase species during film deposition by optical absorption spectroscopy; measurement of concentrations and energies of a broader range of neutral and ionic radicals by molecular-beam mass spectrometry; and correlation of vapor-phase properties to film structure as ascertained by infrared absorption (IR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). Optical and mechanical properties of the deposited films are also measured. This study addresses the synthesis of a number of nitrides that form the basis of "space-age" ceramics. These include cubic boron nitride (c-BN), carbon nitride (C3 N4), gallium nitride (GaN), aluminum nitride (AlN), and the mixed aluminum/gallium nitrides. The unusual mechanical, electrical, and optical properties of these materials make them attractive for many applications, but their wide use is inhibited by the lack of an economic method of s ynthesis.