Anodized porous silicon based humidity sensor: evaluation of material characteristics and sensor performance of AU/PSIO2/AU

Abstract

Porous silicon (PSi) has received a lot of attention in nanotechnology research in recent years for its potential use as sensing layers in sensor application. However, there have been relatively limited studies concerning the effect of varying contact gaps and bias voltages on the humidity sensor based on PSi. In this work, the nanostructure PSi layer was synthesized via the anodization method and fabricated at different annealing temperatures of 250 ℃, 450 ℃, 650 ℃, and 850 ℃. Subsequently, the four samples were deposited with varying gold (Au) contact gaps of 3.5 mm, 4.5 mm, 7.5 mm, and 8.5 mm. The morphological and structural characteristics of the PSi layer were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The PSi-based humidity sensors with varied Au contact gaps were evaluated in a humidity chamber at 40–90% relative humidity (RH) levels with different bias voltages of 2 V, 5 V, and 10 V. The optimized fabricated PSi device was evaluated for its electrical behaviour using I-V measurement under various operating temperatures ranging from 25 °C to 100 °C. The findings showed that the enhanced PSi structure of the 450 °C annealed sensor produced the highest sensitivity performance of 18.4705 µA/%RH with stable output at a contact gap of 4.5 mm and a bias voltage of 10 V. The sensor exhibited a high surface area to volume ratio, which facilitated efficient interactions between surface active sites and water molecules, resulting in a highly sensitive humidity sensor.