Effect of Substrate Temperature on the Structural,Electrical and Optical Properties of Nanocrystalline Silicon Films in Hot-Filament Chemical Vapor Deposition

Hydrogenated nanocrystalline silicon fi1ms are deposited onto glass substrates at different substrate temperatures(140-400℃)by hot-filament chemical vapor deposition.The effect of substrate temperature on the structural properties are investigated.With an increasing substrate temperature,the Raman crystalline volume fraction increases,but decreases with a further increase.The maximum Raman crystalline volume fraction of the nanocrystalline silicon 61ms is about 74%and also has the highest microstructural factor(R=0.89)at a substrate temperature of 250℃.The deposition rate exhibits a contrary tendency to that of the crystalline volume fraction.The continuous transition of the fi1m structures from columnar to agglomerated is observed at a substrate temperature of 300℃.The optical band gaps of the grown thin 61ms declines(from 1.89 to 1.53 eV)and dark electrical conductivity increases(from about 10-10 to about 10-6 S/cm)with the increasing substrate temperature.