Raman scattering spectroscopy for solid-phase and metal-induced crystallization of extremely thin germanium films on glass

Abstract

Raman scattering spectroscopy was applied to characterize polycrystalline germanium (Ge) on noncrystalline substrates fabricated by solid-phase crystallization and metal-induced crystallization (MIC) using copper (Cu) and tin (Sn) as the catalyzer. The subject was focused on the material for thin-film transistors in which the precursors, with the thickness of only 15 nm, were deposited by sputtering. The optical phonon mode exhibited considerable asymmetry and was separated into the following three components: crystal, low-dimensional nanosized crystallite (NC), and amorphous. The width and frequency shift of the crystal component were analyzed using the phonon confinement effect, thermal stress, and Sn composition. The transition from amorphous to the NC state was associated with the disorder in the precursor. The addition of a restrained amount of Cu led to the evident progress of crystallization and simultaneous suppression of the NC transition. The Sn composition of 3 at% was insufficient to exhibit a noticeable MIC effect.