Unveiling a growth temperature-dependent ultra-sensitive tetragonal scheelite BiVO4 thin film-based gas sensor for ammonia volatilization at room temperature

Abstract

Ammonia (NH₃) vapour is considered as a hazardous volatile, which has the potential to cause health concerns in humans. Exposure to NH₃ can lead to potentially fatal, severe burn injuries to human eyes, can cause encephalopathy, and also affects various physiological systems, including the liver, the kidneys and the immune system. Due to these prime factors, the advancement of chemi-resistive ammonia gas sensors at room temperature has drawn considerable attention among researchers. In this current work, tetragonal scheelite (T_s)-BiVO₄ thin films were deposited by varying the substrate (growth) temperature via the chemical spray pyrolysis method. The deposited thin films were subjected to structural, optical, morphological and gas sensing assessment. The gas sensing results indicate that the BV250 film has an ultra-high sensor response (I_gas/I_air = 900 for 75 ppm) towards ammonia vapour at room temperature. The pro-longevity of the sensor is outstanding (I_gas/I_air = 58.2 for 25 ppm) even after 50 days at room temperature. Furthermore, it demonstrates excellent selectivity, rapid response time (190 ± 4 s)/recovery time (16 ± 5 s) and repeatability (up to 4 cycles), and performs well in relatively humid conditions. This study offers insights into T_s-BiVO₄ thin films as a sensing layer in a chemi-resistive gas sensor for ammonia detection at room temperature.