Nanooptics and photonics

Microstructure and luminescence characterization of β-Ga2O3 nanopowders obtained by high-energy mechanical milling
Luchechko A.1*, Shpotyuk Y.1,2, Vasyltsiv V.1, Cebulski J.2, Baláž M.3
1Department of Sensor and Semiconductor Electronics, Ivan Franko National University of Lviv, 107, Tarnavskogo St., 79017 Lviv, Ukraine.
E-mail: luchechko@electronics.lnu.edu.ua
2Institute of Physics, University of Rzeszow, 1, Pigonia St., 35-959 Rzeszow, Poland.
3Institute of Geotechnics, Slovak Academy of Sciences, 45, Watsonova St., 04001 Košice, Slovakia. 

Gallium oxide (β-Ga2O3) is a wide band-gap n-type semiconductor (Eg = 4.9 eV) with controlled conductivity and tunable optical properties. The β-Ga2O3 crystals are a promising material for application in different areas including power electronics, sensors, UV photodetectors, and transparent electrodes. Due to the perfect luminescence properties, β-Ga2O3 has also attracted attention for application in flat panel displays and UV phosphors [1]. At the same time, the large surface-to-volume ratio in low-dimensional β-Ga2O3 structures produces extra properties when compared to bulk materials, thus increasing the areas of applications.
β-Ga2O3 nanopowders prepared by high-energy mechanical milling using different rates are investigated by multi-experimental methods including microstructure characterization using X-ray powder diffraction (XRPD), morphology studies by transmission electron microscopy (TEM) with energy-dispersive spectroscopy (EDS) and high-resolution TEM (HRTEM) as well as luminescent spectroscopy in UV and visible spectral regions.
XRD data reveal that obtained β-Ga2O3 powders belong to a monoclinic crystalline structure with a space group of C2/m. The average crystallite size was calculated depending on the milling rate. Spectroscopic properties, i.e. excitation and emission, were investigated in the 220-800 nm spectral region at room temperature. Photoluminescence spectra contain the broad emission band in UV, blue and green spectral regions. The relative intensity of these emissions depends on milling conditions. Broad and intense luminescence that is explained by the presence of oxygen and gallium vacancies associates show that the nanocomposites are promising candidates for applications as phosphors.

1.	Peaton S.J., Jang J. et al. Appl. Phys. Rev. 5 (2017) 011301.