抛光工艺对硅基Pb_(1-x)Ge_xTe薄膜性能的影响

研究了不同的抛光方法(机械抛光、化学腐蚀及化学机械抛光)对硅基板上沉积的Pb_(1-x)Ge_xTe薄膜性能的影响.研究表明,经化学机械抛光(SiO_2胶体或Cr~+)的硅基板上所沉积的Pb_(1-x)Ge_xTe薄膜具有致密的结构及平直的界面,其沉积速率也比在化学腐蚀抛光表面的沉积速率大7%或18%(分别对应<111>和<100>晶向);薄膜具有明显高于化学腐蚀抛光基板沉积薄膜的折射率,且折射率随温度的降低而增加,而低温下折射率随波长的增加而增加;化学腐蚀抛光基板沉积薄膜的折射率的增加量明显大于化学机械抛光基板沉积薄膜的增加量;薄膜层经机械抛光后,其膜层结构、组分及其深度分布均未改变,但透射率增加,消光系数有所改善,折射率有所降低.

EFFECTS OF POLISHING ON THE PERFORMANCES OF Pb_(1-x)Ge_xTe THIN-FILMS DEPOSITED ON SI SUBSTRATE

The influences of different polishing methods (mechanical, chemical etching method or chemical/mechanical) on the characteristics of Pb1-xGexTe thin films deposited on Si substrate were studied. It is found that Pb1-xGexTe thin films deposited on Si substrates which are polished by chemical/mechanical polishing (SiO2 or Cr^＋ colloid) have a denser structure and flat interface, and they have also a deposition rate of 7% or 18% greater than those deposited on the surfaces of Si substrates polished by chemical etching for the directions of 〈 111 〉 and 〈 100 〉, respectively. Moreover, this thin film has a higher refractive index than those deposited on the surfaces of Si substrates polished by chemical etching, and the refractive index increases with the decrease of temperature. At low temperature, the refractive index increases with the increasing of wavelength. The change of refractive index for the substrates polished by chemical etching is greater than that for the substrates polished by chemical/mechanical one. The crystal structure, composition and element depth-profile of Pb1-xGexTe thin film remain unchanged after surface is polished by mechanical polishing, while optical transmission of this thin film is increased, and extinction coefficient and refractive index are decreased.