Chromium-Induced Nanocrystallization of a-Si Thin Films into the Wurtzite Structure

Abstract

Chromium metal-induced nanocrystallization of amorphous silicon (a-Si) thin films is reported. The nanocrystalline nature of these films is confirmed from X-ray diffraction and Raman spectroscopy. Significantly, the deconvolution of Raman spectra reveals that the thin films were crystallized in a mixed phase of cubic diamond and wurzite structure as evidenced by the lines at 512 and 496 cm−1, respectively. The crystallite sizes were between 4 to 8 nm. Optical properties of the crystallized silicon, derived from spectral transmittance curves, revealed high transmission in the region above the band gap. Optical band gap varied between 1.3 to 2.0 eV depending on the nature of crystallinity of these films and remained unaltered with increase in Cr addition from 5 to 30%. This signifies that the electronic structure of the nanocrystalline Silicon films is not affected considerably inspite of the presence of metal silicides and the process of crystallization.