EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Gallium oxide (Ga2O3) is a wide bandgap semiconducting material with application in the fields of high power, high temperature and gas sensing electronic devices. In this work we report the selective and fast detection of relative humidity at room temperature by chemoresistive gas sensors based on individual β-Ga2O3 nanowires (NWs), with negligible response to other gases. The synthesis has been carried out by a vapor-liquid-solid (VLS) method from mixtures of Ga2O3 powder and graphite, which produces core β-Ga2O3 NWs surrounded by a 4-10 nm-thick amorphous carbon shell. The measured room-temperature resistance variation as a function of relative humidity concentration can only be explained by the adsorption-desorption gas-solid reactions taking place at this carbon shell, as the commonly accepted interaction mechanisms for β-Ga2O3 occur at temperatures in excess of 150 ºC. The interpretation of the NW material’s response to changes in humidity can be related to the surface composition on the semiconductor NWs. Similarities to carbon-based sensor performance can be traced back to the carbon enrichment on the surface as a feature of the carbothermal reduction method used.