微波高功率对生长金刚石膜影响的研究

Effect of Microwave Power on Diamond Film Growth

在实验室自制的10 kW微波等离子体化学气相沉积装置中,系统分析提高功率对生长金刚石膜的影响。利用等离子体发射光谱诊断分析高功率微波等离子体放电环境的特征,同时采用扫描电镜及Raman光谱对不同功率条件下获得的金刚石膜的形貌和质量进行表征。结果表明:微波功率的提高可以获得面积更大的强场区域,为金刚石的大面积均匀成膜提供了有利条件;同时提高微波功率可以产生更高的电子密度,激发更多的活性氢原子和有利于金刚石生长的含碳基团;在气压为15 kPa,H2/CH4流量比为200∶6 mL/min的条件下,当功率由4000上升到5000 W时,金刚石膜的质量明显得到提高;当功率升高到5500 W时,金刚石质量开始下降,出现孪晶;但在升高功率的过程中,晶粒尺寸增大的趋势没有改变。因此,提高微波功率易于活性氢原子的产生并可更为充分的活化含碳大分子基团;在本实验条件下,当微波功率为5000 W时,所制备的金刚石膜可具有较高的质量。

Diamond thin films were synthesized by plasma assisted chemical vapor deposition in the lab-built 10 kW microwave reactor.The influence of the microwave power on the microstructures of diamond coatings were investigated with scanning electron microscope,Raman spectroscopy and plasma optical emission spectroscopy.The results show that the microwave power has a major impact.For instance,as the power increased,the quality of diamond coating changed in an improvement-deterioration manner accompanied by increasing grain-size,because of larger area of strong field and because of density increases of electron,active H-atoms and C-containing radicals.Deposited at 15 kPa and with H2/CH4=200 mL/min,a power increase in 4~5 kW range significantly improved the diamond film quality,and the optimized power was estimated to be 5 kW;however,above 5.5 kW,an increase of power resulted in quality deterioration of diamond film,possibly due to twin-crystal formation.