Kinetic study of the thermal quenching of the ultraviolet emission in Zn_2GeO_4 microrods

Abstract

Zn_2GeO_4 microrods obtained by thermal evaporation of a compacted powder mixture of ZnO and Ge exhibit quite intense UV luminescence at low temperatures. Herein, the luminescence properties of Zn_2GeO_4 microrods are studied for 2:1 and 1:1 ZnO:Ge ratio in the precursor mixture. In both cases, Zn2GeO4 microrods of high crystal quality produce a 355 nm emission under aforementioned bandgap excitation conditions at low temperatures. However, this emission vanishes at room temperature (RT) in the 1:1 samples while it is kept in the 2:1 ones. Herein this work, the thermal quenching of the UV luminescence is studied by means of steady and time-resolved photoluminescence techniques from 4 K up to RT for both Zn_2GeO_4 microrods. The analysis of the results leads us to conclude that although the luminescence mechanisms are the same in both cases, a higher decay rate is observed in the 1:1 in both intensity and lifetime, which explain the observed thermal quenching at RT.