Chapter 13 Pressure Effects on the Local Atomic Structure

Abstract

This chapter discusses the experimental results on the pressure-induced effects of local order of amorphous hydrogenated silicon (a-Si:H) films and the pressure-induced phase transitions from semiconductor to metal. The chapter describes high-pressure experimental techniques, the local order derived from the disorder-induced Raman spectra, the local order in terms of X-ray diffraction intensity profiles, and pressure-induced phase transitions and the associated changes in optical energy gap, electrical resistivity, and atomic structure. Plasma-deposited a-Si:H films demonstrate the systematic changes in local order and gap states with H concentration, C H , which depend critically on the preparation method and preparation condition. The glow-discharge plasma of silane has been studied for understanding the nucleation and growth kinetics of a-Si:H films. The emission spectra are identified in terms of primary ions produced by electron impact and secondary ions produced by ion–molecule reactions. The growth rate of a-Si:H films, however, depends on the neutral radicals rather than ions. The nucleation and growth are strongly influenced by electron and ion Bombardment.