Temperature-dependent photoluminescence of r-GeO2 film deposited on r-plane sapphire by synchrotron radiation excitation

Abstract

Germanium oxide (GeO2) film has been directly deposited on r-plane sapphire substrate by pulsed laser deposition. Firstly, the structure, surface morphology, and optical properties of the film have been systematically investigated by means of X-ray photoelectron spectroscopy, X-ray diffraction, Raman scattering, and atomic force microscope. The measurements results suggest that the deposited pure GeO2 film has the rutile structure with a (101) orientation. Subsequently, temperature-dependent photoluminescence was detailedly investigated by synchrotron radiation excitation. Photoluminescence spectrum at 30 K exhibits a broad blue–green emission band, which can be divided into three emission peaks at about 3.0 eV (∼415 nm), 2.7 eV (∼455 nm), and 2.4 eV (∼514 nm). As the temperature increases, these defect-related emissions experience strong thermal quenching and distinct red-shift. The variation of emission intensity and wavelength with the temperature follows the exponent equation and Bose-Einstein expression, respectively. These experimental data will provide reliable guiding value for developing r-GeO2 material.