Theoretical analysis of electronic band structure of 2-to-3-nm Si nanocrystals

TL;DR

This paper presents a new method to reconstruct and analyze the electronic band structure of silicon nanocrystals up to 3 nm in size, considering surface effects and geometric relaxation, to better understand their luminescence properties.

Contribution

It introduces a general approach for band structure reconstruction from real-space calculations and applies it to large-scale DFT studies of silicon nanocrystals, revealing size and surface effects.

Findings

Band structure is applicable to silicon nanocrystals larger than ~2 nm.

Surface passivation and geometric distortion significantly affect electronic properties.

The method provides insights into luminescence behavior based on structural factors.

Abstract

We introduce a general method which allows reconstruction of electronic band structure of nanocrystals from ordinary real-space electronic structure calculations. A comprehensive study of band structure of a realistic nanocrystal is given including full geometric and electronic relaxation with the surface passivating groups. In particular, we combine this method with large scale density functional theory calculations to obtain insight into the luminescence properties of silicon nanocrystals of up to 3 nm in size depending on the surface passivation and geometric distortion. We conclude that the band structure concept is applicable to silicon nanocrystals with diameter larger than $\approx$ 2 nm with certain limitations. We also show how perturbations due to polarized surface groups or geometric distortion can lead to considerable moderation of momentum space selection rules.