Synthesis of Low-Defct Diamond Films

利用电容耦合射频（13.56MHz）等离子体气相沉积装置和红外辐射加热器，制备了尽可能低缺陷的金刚石薄膜。在乙醇和氢气的总流量为100 sccm、放电功率为500 W、总气体压力、乙醇浓度、加热温度和添加气体流量等条件下制备膜。通过拉曼光谱中的非金刚石成分和ESR中的自旋密度对薄膜中的缺陷进行了评价，得到了以下结果：(1)加入0.5%的四氟化碳，保持0.5%的乙醇浓度，即使在350℃的低温下也能生长出不含非金刚石成分的高质量薄膜。该薄膜的自旋密度为1.6*10^<18> cm^<-3>。(2)上述情况下温度升高。最高质量的薄膜在550℃时生长。该薄膜的自旋密度为5.2*10^<17>cm^<-3>，是本项目中最低的。(3)当乙醇浓度为1.0%，温度为350℃时，加入0.2%的四氟化碳可获得较高质量的薄膜。该薄膜的自旋密度为7.3*10^<17>cm^<-3>。与上述情况相反，当温度升高时，薄膜会降解。(4)在加入四氟化碳形成的等离子体的光学发射光谱测量中，当乙醇浓度分别为0.5%和1.0%时，C_2和CH自由基的数量增加。(5)当源气体中加入氮气时，在某些情况下观察到自旋密度和非金刚石成分的降低。在改善薄膜质量方面，氮的效果不如四氟化碳。

The synthesis of diamond films with defects as low as possible was performed using a capacitively coupled rf (13.56MHz) plasma CVD apparatus and an infrared-radiation heater. The films were prepared at various conditions keeping the total-flow rate of ethyl alcohol and hydrogen at 100 sccm and discharge power at 500 W and varying total-gas pressure, ethyl alcohol concentration, heating temperature and flow rate of added gas. Defects in the films were evaluated by nondiamond components in Raman spectrum and spin density in ESR,and the following results were obtained.(1) When a 0.5% carbon tetrafluoride is added keeping the concentration of ethyl alcohol at 0.5%, a high-quality film without nondiamond components grows even at a low temperature of 350ﾟC.The spin density of this film is 1.6*10^<18> cm^<-3>.(2) The temerature is increased in the above case. The highest-quality film grows at 550ﾟC.The spin density of this film is 5.2*10^<17>cm^<-3>, which is lowest in the present project.(3) When the concentration of ethyl alcohol and the temperature are kept at 1.0% and 350ﾟC,respectively, the highesr-quality film is obtained if a 0.2% carbon tetrafluoride is added. This film has a spin density of 7.3*10^<17>cm^<-3>. In contrast with the above case, the film degrades when the temperature is increased.(4) In the measurement of optical emission spectrescopy for the plasma formed by adding carbon tetrafluoride, an increase in the amount of C_2 and CH radicals is observed when the concentration of ethyl alcohol is 0.5 and 1.0%, respectively.(5) When nitrogen is added into the source gas, reduction in the spin density and the nondiamond component is observed in some cases. For improvement in film quality, nitrogen is not so effective as the carbon tetrafluoride.