Humidity sensor based on Ga2O3 nanorods doped with Na+ and K+ from GaN powder

Abstract Gallium oxide (Ga2O3) nanorods were prepared from commercial gallium nitride (GaN) powder via the simple thermal annealing method by one step, and they were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy (EDS). The thick film humidity sensors were prepared by spin-coating the sensing materials on Al2O3 ceramic substrates coated with Ag–Pd interdigitated electrodes and the humidity sensing properties were studied in detail. The as-prepared Ga2O3 nanorods are of diameters 40–100 nm and lengths 1–6 μm, and they are doped with Na+ and K+, successfully. The impedance variation of Ga2O3 nanorods sensor with the humility exhibits good linearity response about four orders of magnitude, when the relative humility (RH) is changed from 11% to 95% at 100 Hz. Response and recovery times are about 6 s and 21 s and the maximum hysteresis is only 3% RH at 100 Hz. The good humility sensing properties may be attributed to the synergistic effect of Ga2O3 nanorods and the ions doping.