Development of Diamond Film Synthesis at Room Temperature

在本财政年度，金刚石膜通过脉冲调制ECR等离子体化学气相（CVD）沉积法合成，该方法使用磁活性微波等离子体CVD系统，该系统配备有最大功率为5kW的微波功率源和红外激光吸收光谱（IRLAS）系统。在磁激活微波等离子体化学气相沉积中进行了光发射光谱和红外光谱测量，发现最大微波功率为5 kW的脉冲调制等离子体化学气相沉积金刚石膜的生长速率是时均微波功率为2.5 kW的连续等离子体化学气相沉积金刚石膜的3倍，并通过光谱测量研究了脉冲调制等离子体对金刚石膜生长的促进机理。生长速率在500 Hz处有一个急剧的峰值。实验结果表明，脉冲操作使甲烷的时均浓度增加。而甲基（CH_3）自由基密度的变化并不像频率变化那样剧烈。脉冲对金刚石生长的促进作用不仅与CH_3浓度有关，还与其它物种的增加有关，在光发射谱中观察到余辉中氢自由基（H）的寿命约为1ms。1ms的周期与最合适的调制频率一致，即，500赫兹。这些结果暗示了H自由基在金刚石生长中的重要性。金刚石膜的低温制备，几乎是通过使用金刚石核的籽晶来实现的。在低于200 ℃的Si衬底上成功地制备出了具有良好刻面结构的金刚石薄膜。

In this fiscal year, diamond films were synthesized by pulse modulated ECR plasma chemical vapor (CVD) deposition method using a magneto-active microwave plasma CVD system equipped with a microwave power source of 5 kW in maximum power and a infrared laser absorption spectroscopy (IRLAS) system. Optical emission spectroscopy and IRLAS measurement were also carried out in the magneto-active microwave plasma CVD.The growth rate of the diamond films by the pulse modulated plasma CVD with a maximum microwave power of 5 kW was three times as large as one of the continuous plasma of time averaged microwave power (2.5 kW) .The pulse modulated plasma was investigated by spectroscopic measurements to reveal the enhancing mechanism. The growth rate showd a drastic peaking at 500 Hz in frequency. It was observed that the time averaged CH_3 density was increased by the pulse operation. However, the methyl (CH_3) radical density did not show such a drastic change as changed the freqency was. The enhancement of diamond growth must be explained not only by the CH_3 density but also the other species enhanced by the pulse operation.It was observed in the optical emission spectroscopy that the life time of the Hydrogen radical (H) was about 1 ms in the after glow. The period of 1 ms agree with the most suitable modulation frequency, i.e., 500Hz. These result imply the importance of H radical in the diamond growth.The goal of this research, i.e., low temperature fabrication of diamond films, was almost achieved by using nanocrystal seeding for diamond nuclei. Well faceted diamond films were successfully fabricated on the Si substrates below 200ﾟC.It was concluded that the prevention of polymerization on the substrates was a key point to decrease the growth temperature.