Gradient etching of silicon-based thin films for depth-resolved measurements: The example of Raman crystallinity

Abstract

An etching procedure was applied to microcrystalline silicon (pc-Si:H) thin films in order to obtain a wedge-shaped profile for depth-resolved characterization. A microfluidic flow cell that merges deionized water with a potassium hydroxide solution (KOHaq) was utilized. The samples consisted of texture-etched ZnO:Al on a Corning Glass substrate, a microcrystalline p-doped layer serving as seed layer and the investigated intrinsic microcrystalline or amorphous silicon (a-Si:H). Along the etched profiles, microscopic Raman spectroscopy was used to estimate the crystalline volume fraction X, for samples deposited with intentionally varied silane concentration to investigate the a-Si:H/mu c-Si:H and mu c-Si:H/a-Si:H transition. (C) 2011 Elsevier B.V. All rights reserved