Varied longitudinal microstructure of μc-Si:H films by tuning substrate temperature

Abstract

Hydrogenated silicon thin films were deposited using plasma enhanced chemical vapour deposition method. The effects of substrate temperature on the microstructure and electrical properties of the films were investigated. Results show that the as received crystalline silicon thin film is a typical two-phase structure consisting of an amorphous phase and a crystalline phase. At a lower substrate temperature, the thickness of the initial amorphous incubation layer is dozens of nanometers, and few crystalline grains inset in the film after phase transition. As the substrate temperature increases, the initial incubation stage shortens to several nanometers, and the phase transition to crystalline starts earlier. After the phase transition, abundant crystallites appear, and the amorphous phase exists in the film just as the grain boundary. However, at overhigh substrate temperature, the average crystallinity and grain size of the film decrease. Deposition rate abidingly decreases with the increase in substrate temperature. The films with more ordered structure exhibit superior electrical properties.

Keywords:

• Silicon thin films
• PECVD
• Longitudinal microstructure
• Phase transition
• Electrical property