Thermal emission of hydrogenated amorphous silicon microspheres in the mid-infrared

TL;DR

This study investigates the mid-infrared thermal emission of hydrogenated amorphous silicon microspheres, revealing phononic peaks, stability under excitation, and a phase change to polycrystalline silicon at higher intensities.

Contribution

It provides new insights into the thermal emission properties and phase transitions of hydrogenated amorphous silicon microspheres under laser excitation.

Findings

Pronounced phononic peak at 2000 cm-1 linked to silicon-hydrogen bonds

Emission signal remains stable at moderate excitation levels

Phase transition from amorphous to polycrystalline silicon at high excitation

Abstract

Hydrogenated amorphous silicon microspheres feature a pronounced phononic peak around 2000 cm-1 when they are thermally excited by means of a blue laser. This phononic signature corresponds to vibrational modes of silicon-hydrogen bonds and its emitted light can be coupled to Mie modes defined by the spherical cavity. The signal is apparently quite stable at moderate excitation intensities although there appeared some signs pointing to hydrides bonds reconfiguration and even hydrogen emission. Above a certain excitation threshold, a phase change from amorphous to poly-crystalline silicon occurs that preserves the good structural quality of the microspheres.