Structure and spatial distribution of Ge nanocrystals subjected to fast neutron irradiation

TL;DR

This study examines how fast neutron irradiation affects the structure and distribution of germanium nanocrystals in silica, revealing damage and recovery processes through multiple characterization techniques.

Contribution

It provides new insights into the effects of neutron irradiation and annealing on Ge nanocrystals embedded in silica, including structural damage and redistribution patterns.

Findings

Neutron irradiation partially destroys Ge nanocrystals.

Annealing at 800°C restores crystallinity.

Distribution of nanocrystals shifts away from the surface after treatment.

Abstract

The influence of fast neutron irradiation on the structure and spatial distribution of Ge nanocrystals (NC) embedded in an amorphous SiO2 matrix has been studied. The investigation was conducted by means of laser Raman Scattering (RS), High Resolution Transmission Electron Microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). The irradiation of NC-Ge samples by a high dose of fast neutrons lead to a partial destruction of the nanocrystals. Full reconstruction of crystallinity was achieved after annealing the radiation damage at 800 deg. C, which resulted in full restoration of the RS spectrum. HR-TEM images show, however, that the spatial distributions of NC-Ge changed as a result of irradiation and annealing. A sharp decrease in NC distribution towards the SiO2 surface has been observed. This was accompanied by XPS detection of Ge oxides and elemental Ge within both the surface and subsurface region.