Impact of sublayer thickness and annealing on silicon nanostructures formation in a-Si:H/a-SiNx:H superlattices for photovoltaics

Abstract

In this work, we synthesized amorphous multilayered a-Si:H/a-SiN x :H superlattices with different thickness of sublayers grown on silicon and quartz substrates by PECVD method at low power density (60 mW/cm 2) and subtrate temperature (250°C) using nitrogen and silane gases as reactive precursors. Subsequently, the post-deposition annealing of these structures, composed of alternating layers of a-Si:H and a-SiN x :H, was carried out up to 1100° in vacuum to form silicon nanostructures. The dependence of the structural and chemical bonding characteristics of prepared superlattices on the silicon sublayer thickness and post-deposition annealing temperature was investigated. The formation of silicon nanostructures was confirmed by transmission electron microscopy, X-ray diffraction measurement and Raman scattering spectroscopy. Changes in bonding configuration during the annealing were carried out by Fourier transform infrared spectroscopy. Optical properties were studied by UV-Vis spectroscopy. XRD, Raman and TEM measurements show that the crystallization process of a-Si:H sublayers strongly depends on the thickness of initial a-Si:H sublayers and the post-deposition treatment process. It was found that a higher crystallization temperature for the thinner a-Si:H sublayers is needed. Results clearly show that structural and optical characteristics of these systems can be controlled by deposition parameters and post-deposition annealing conditions.

On KCN treatment effects on optical properties of Si-based bilayers

“…Thin film structures based on amorphous (a-Si) or microcrystalline (mc-Si) thin film silicon have become reliable materials in many electronic and optoelectronic devices, such as solar cells, thin film transistors (TFF), LCD etc [1][2][3]. In a-Si and mc-Si solar cells conversion efficiency and its stability are strategic issues because their optical and electrical properties suffer from lightinduced degradation caused by dangling or week bonds [4].…”

FTIR Analysis of Electron Irradiated Single and Multilayer Si₃N₄ Coatings

“…Fourier transform infrared spectrometry (FTIR) has been used for identification of presence of Si-N bonds [8]. The FTIR attenuated total reflection (FTIR-ATR) has been previously used for analysis of the Si 3 N 4 -bioglass composites [9] and combined Hf-based-SiN x materials [10], multilayered silicon nitride materials for photovoltaics [11] and atomic-layer deposited silicon nitride [12].…”