Study of the Laser-stimulated carbon-hydrogen reaction process in gas-phase diamond growth

自气相金刚石生长方法实用化以来，已经走过了很长一段时间，但对其生长机理的详细认识至今仍不清楚。这部分是因为生长过程包含许多基本过程，如气体的解离、吸附、扩散等，这些过程都是以复杂的方式相互影响的。然而，例如在制造双金属半导体器件的情况下，需要在原子尺度上控制金刚石的生长。因此，本研究旨在研究气相金刚石生长中激光选择性激发的简单碳氢反应过程。首先，为了跟踪反应器中源气体分压的变化，新设计了Farvitron型质谱仪。感兴趣的气体物种是甲醇及其碎片，约40的质量分辨能力足以分析这些气体物种。Favitron型光谱仪结构简单，对低质量组分具有较高的灵敏度，非常适合用于这一目的。新开发了比传统类型更简化的Favitron。离子振荡采用V型电势，气体电离的后减速型电子枪垂直于离子路径。电子束通过射频变压器调制Whenelt Baias势而被斩波。结果，获得了1.4 mA的电子束电流，这足以满足我们的目的，并保证了稳定的束流斩波，最高可达100 kHz。

Long time has passed since the method of the gas-phase diamond growth began to be practically used, but the detail of the growth mechanism has not been clarified even now. This is partially because the growth process contains many elementary processes such as the gas dissociation, adsorption, diffusion and etc. which are all influenced each ohter in the complicated manner. However it will be necessary to control the diamond growth in atomic scale, for example, in the case of fabrication of the dimamond semiconductor device. In this study, therefore, it is aimed to investigate the simple carbon-hydrogen reaction process by using selevtive exitation by laser irradiation in the gas-phase diamond growth.First of all, In order to trace the variation of the partial pressure of source gases in the reactor, Farvitron type mass spectrometer was newly designed. Interested gas species are methanol and its fragments, and the mass resolving power of about 40 is enough for analysis of these gas species. Favitron type spectrometer is very adequate for this purpose because of its simple structure and high sensitivity for lower mass species. More simplified Favitron than conventional type was newly developed. The V-shaped potential for oscilation of ion was employed, and the post deaccelerated-type electron gun for ionzation of gas species was atached normal to the ion path. The electron beam was chopped by modulate the Whenelt baias potentail using radio frequency transformer. As a result, 1.4 mA of electron beam current, which is enough for our purpose, was obtained, and stable beam chopping upto about 100 kHz was confirmed.