Humidity sensing investigation of chromium- doped titanium dioxide nanomaterial

Abstract Nowadays, humidity sensors are used in electronic skin, noncontact sensing, and respiratory analysis, and have become interesting areas of study since COVID-19. Humidity sensors are used in modern technology, including artificial intelligence (AI) and the Internet of Things (IoT). So, the study of humidity sensor is an urgent need for the society as well as rapidly growing technology. This study presents the synthesis, characterization and application of chromium (Cr)-doped titanium dioxide (TiO 2 ) in thin film humidity sensor. The Cr-doped TiO 2 nanomaterials are synthesized by sol–gel process. The synthesized nanomaterials were characterized using powder x-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive x-ray (EDX), Brunauer–Emmett–Teller (BET) techniques and Raman spectroscopy. The PXRD study shows that the crystallite size decreases from 29.35 to 19.56 nm with the concentration of chromium. FTIR spectroscopy reveals the characteristic vibrational frequency of anatase titania and different functional groups present in the sample. The surface morphology was investigated by FESEM which elucidate that as chromium is doped in titania up to 10 at% it increases the grain growth which produces smaller and uniform particles. At 15 at% the dopant promotes fusion of particles. The EDX study signifies the elemental composition. The BET technique divulges the surface characteristics. The evaluated specific surface area and porosity values vary from 40.99 to 84.21 m 2 g −1 and 2.41 to 4.11 nm, respectively. Raman study confirms the formation of the anatase phase of titanium dioxide. The optimized Cr-doped TiO 2 nanomaterial was explored as a thin film humidity sensor for the first time. Different sensing parameters of the designed sensor were determined and studied, and it was found that the designed sensor had a minute ageing effect of 1.19%, good repeatability of 98.76%, hysteresis error 5.77, and response and recovery times of 61.6 and 66.7 s, respectively. The developed sensor has promising attributes regarding material, recovery, and response times.