Hydrogenation-assisted nanocrystallization of amorphous silicon by radio-frequency plasma-enhanced chemical vapor deposition

Abstract

The effects of plasma-enhanced hydrogenation on the crystallization of pure, electron-beam evaporated amorphous silicon (a-Si) at temperatures as low as 300°C were investigated. Successive steps of hydrogenation in the plasma-enhanced chemical vapor deposition chamber, and in situ annealing in a N2 ambient environment were applied to the a-Si samples over a range of low temperatures and plasma powers. At specific plasma-power densities, nanocrystalline silicon layers with an average grain size of less than 10nm were formed where their size, distribution, and porosity could be varied by altering the plasma power and hydrogenation temperature. The surface morphology and the nanocrystalline quality of the samples were characterized using scanning electron microscopy, dark-field transmission electron microscopy, and electron diffraction. In addition, by plasma-enhanced oxidation at a temperature of 250°C, a thin layer of oxide was grown and its physical, structural, and electrical characteristics were investigated.