甲烷浓度对CVD金刚石薄膜晶体学生长过程的影响

采用X射线衍射技术、电子背散射衍射技术和扫描电镜分别观察了不同甲烷浓度条件下沉积的CVD自支撑金刚石薄膜的宏观织构、微区晶界分布和表面形貌.研究了金刚石晶体{100}面和{111}面生长的晶体学过程.研究表明,{100}面通过吸附活性基团CH^2- 2,而{111}面通过交替吸附活性基团CH^-3和CH^-3后脱氢堆积碳原子.低甲烷浓度时,{111}面表面能低于{100}面,使{111}面生长略快于{100}面.甲烷浓度升高,动力学作用增强使{100}面生长明显快于{111}面,使金刚石薄膜产生{100}纤维织构;同时显露的{100}面平行于薄膜表面,竞争生长使位于晶体侧面的{111}面由于相互覆盖而减小,形成了不同于单晶体自由生长的薄膜表面形貌组织.

Influence of Methane Concentration on Crystal Growing Process in CVD Free Standing Diamond Films

The Macro-texture, grain boundary distribution and surface morphlolgy in CVD free standing diamond films deposited with different methane concentrations were observed by X ray diffraction technology, electron backscatter diffraction and SEM. The crystal growing process of {100} and {111} planes in diamond crystal was studied. It is shown that diamond films adsorb activated radical CH2 2-on {100} plane or adsorb CH3- and CH3- on {111} plane alternately. Carbon atoms stack on the film surface during dehydrogenation. At low methane concentration, the expansion ratio of {111} planes is close to, but faster than that of {100} planes because of their relative lower surface energy. The enhanced driving force induced by the increased methane concentration results in faster growth of {100} plane than that of {111} plane, which promotes the formation of {100} texture. The film surface morphology consisits of the exposured {100} planes that are parallel to the film surface and the exposured {111} planes area as the side surface that decrease during the competition growth, which is different from that of single crystal growth.