Growth of microcrystalline Si and (Si, Ge) on plastic substrates

We report on the growth and properties of microcrystalline Si and its alloys on polyimide substrates. The materials were grown using low pressure, remote ECR plasma deposition. The crystalline fraction of the films was measured using Raman measurements, electrical properties using activation energy, dark conductivity and photo-conductivity and absorption using spectrophotometer and two-beam photo-conductivity. The best crystallinity was obtained when the substrates were conducting, coated with a thin Mo film. Attempts to deposit directly on plastic substrates produced amorphous films. However, the use of an amorphous (Si,C) or doped a-Si buffer layers between the plastic substrate and the microcrystalline film improved the crystallinity. We assume that the improved crystallinity on metal-coated polyimide is an indication of the affect of ion bombardment on promoting crystallinity.