The Influence of Silicon Nanoclusters on the Optical Properties of a-SiNx Samples: A Theoretical Study

TL;DR

This theoretical study uses ab-initio calculations to analyze how silicon nanoclusters and Si-N bonds influence the optical properties of a-SiNx samples, revealing the matrix's dominant role in photoluminescence.

Contribution

It provides new insights into the optical behavior of a-SiNx with embedded nanoclusters, emphasizing the matrix's role over the nanoclusters in photoluminescence.

Findings

Optical absorption gap varies with Si-N bond concentration.

Radiative recombination rate is minimally affected by nanoclusters.

Si-N-Si bonds at the interface significantly influence photoluminescence.

Abstract

By means of ab-initio calculations we investigate the optical properties of pure a-SiN$_x$ samples, with $x \in [0.4, 1.8]$, and samples embedding silicon nanoclusters (NCs) of diameter $0.5 \leq d \leq 1.0$ nm. In the pure samples the optical absorption gap and the radiative recombination rate vary according to the concentration of Si-N bonds. In the presence of NCs the radiative rate of the samples is barely affected, indicating that the intense photoluminescence of experimental samples is mostly due to the matrix itself rather than to the NCs. Besides, we evidence an important role of Si-N-Si bonds at the NC/matrix interface in the observed photoluminescence trend.