Identifying the Performance of Porous Silicon Based Humidity Sensors at Different Gold Contact Pad Spacings

In recent years, porous silicon (PSi) substrate has been broadly studied by other researchers for microelectronics development due to its viable physical and chemical stability qualities. However, most of the studies published were primarily concerned with the synthesis, characterization, and uses of PSi. The influence of varying metal contact pad distances on humidity sensing performance was discovered to be rarely addressed in the current day. Therefore, this paper aims to investigate the influence of gold (Au) contact pad spacing on PSi in terms of the sensitivity and stability performance of humidity sensor application. In this study, PSi is synthesised via anodization and annealed at 250°C for 1 hour prior to humidity testing. The crystallinity of PSi was characterized using x-ray diffraction (XRD) analysis, which revealed a strong intensity of Si substrate diffraction peak at 69.3° (400) and a minor peak of cubic SiO 2 at 33.1° (111) with low crystallinity. The sensor was tested for humidity detection in the 40% to 90% RH range using different contact gaps. Based on the results, the largest contact gap of 8.5 mm demonstrated the greatest sensitivity performance and output stability in comparison to the shorter contact gaps. The effect of varying the gap was visible in the current versus time graph of each RH level, with a significant decline in the device’s sensitivity as the gap decreased. Thus, our results imply that the emission area expands as the gap width widens due to the increased availability of oxygen vacancies and active sites for electron mobility.