Stimulated Emission in Vertically Aligned Hexagonal ZnO Microcrystals Synthesized by Magnetron Sputtering Method

This study is devoted to the luminescence and stimulated emission properties of the ZnO hybrid structure, which is vertically aligned microcrystals with the [0001] crystallographic orientation and a pronounced hexagonal shape formed on a continuous layer of micron thickness. These microcrystals are up to 10 mu m high and up to 8 mu m in diameter and form the main part of the structure's thickness. The structure was synthesized on the M(10(1) over bar0) plane of sapphire using the magnetron sputtering method. Luminescence of the structure, represented only by conventional near-UV and green components under low-intensity continuous photoexcitation, confirms its high structural and optical quality. Under pulsed photoexcitation with relatively high intensity, stimulated emission (SE) was observed from the structure in the near-UV region at room temperature. The threshold power density for SE was 0.1-0.2 MW/cm(2). Exceeding the threshold leads to a significant increase in the emission intensity compared to the control film without [0001] microcrystals, also grown on M(10(1) over bar0) sapphire. It was assumed that the optical gain is provided by the whispering gallery modes of individual [0001] microcrystals as a result of inelastic exciton-electron scattering, at least at near-threshold excitation intensities.

Automated summary

This study investigates the luminescence and stimulated emission properties of a ZnO hybrid structure. The structure exhibits conventional near-UV and green luminescence under low-intensity continuous photoexcitation, indicating high structural and optical quality. Under pulsed photoexcitation with relatively high intensity, stimulated emission is observed in the near-UV region of the structure.