Isotope effects in amorphous silicon thin films produced by Ar-SiH4 -D2 plasma chemical vapor deposition method

Abstract

Ar-SiH4 -D2 gas mixture positive column plasmas and the deposition of (a-Si:D/H) thin films are investigated. Deuterated amorphous silicon thin films (a-Si:D/H) are produced in an Ar(95%)-SiH4(2.5%) -D2(2.5%) mixed gas plasma by employing dc positive column plasma chemical vapor deposition techniques. A twin probe electric field measurement is used to determine the plasma parameters. The reaction chamber wall temperature is measured by an infrared (IR) image camera. The results indicate that the uniformity of plasma is excellent; the wall temperature of the reaction chamber is nonuniform; and the deposition rate increases with increasing discharge power and gas pressure. The optical characteristics of isotopically different a-Si:H/a-Si:D films are also studied. The results show that the optical band gap of a film has a nonmonotonic thickness dependence with a significant isotope effect.