Development of Diamond Film Synthesis at Room Temperature

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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.