Quantification of Si Dopant in β-Ga2O3-Based Semiconductor Gas Sensors by Total Reflection X-Ray Fluorescence Spectroscopy (TXRF)

Abstract

The development of chemical sensors is relevant for solving environmental problems of monitoring the atmosphere of cities and industrial zones. Semiconductor sensors based on metal oxides are promising chemical gas sensors owing to their high sensitivity, low cost, small size, and low energy consumption. The first attempts at pilot operation of atmospheric air monitoring systems based on such sensors revealed insufficient response stability. Doping of the basic material with silicon can solve the problem. At the same time, data on the amount and distribution of the dopant in the material are necessary to determine the relationship “synthesis conditions–composition–properties.” We propose an approach to the determination of the composition of novel semiconductor materials based on β-Ga₂O₃ with a silicon dopant content from 0.5 to 2 at %. The approach included grinding of samples using a planetary mill and preparation of suspensions in ethylene glycol, followed by TXRF determination of the analytes on sapphire substrates using the method of absolute contents (Si) with S_r of 0.08 and the method of external standard (Ga) with S_r of 0.04. X-ray fluorescence analysis of the samples was performed using an S2 PICOFOX spectrometer (Bruker Nano GmbH, Germany). MoK_α radiation was used to excite X-ray fluorescence. The spectrum acquisition time was 250 s. It is shown that the homogeneity of the dopant distribution in the material can be estimated using the analysis of the suspensions. The studied materials demonstrate an irreproducible sensory response which we associate with the revealed inhomogeneity of the silicon distribution over the surface of β-Ga₂O₃.