Chemical etching of nanocomposite metal-semiconductor films monitored by Raman spectroscopy and surface probe microscopy

Abstract

The complementary tools of atomic force microscopy (AFM) and Raman spectroscopy are used to extract information on the microstructural properties of nanocomposite n-doped Si (n-Si) and Ag/n-Si films deposited on Si(111) substrates at 400 °C and 550 °C. AFM measurements indicated that Ag/n-Si films had grain sizes and roughness values one order of magnitude higher than n-doped Si films. The onset of metal-mediated crystallization of a-Si in Ag/n-Si films at ~ 400 °C is confirmed by Raman spectroscopy. Spectral Raman red-shifts of the transverse optical phonon region compared to monocrystalline silicon originate from the interplay of phonon confinement and higher defect density caused by n-type doping. Two protocols using the etchants ammonium fluoride - HF (2%::4%) and ammonium citrate- acetic acid-hydrogen peroxide (2.5%::2.5%::2%) solutions were investigated. A comparison between non-etched and etched films showed little variability in roughness indicating retention of the microstructure.