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

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.