Detection of acetone vapours using solution-processed tin oxide thin-film transistors

Abnormal concentrations of volatile organic compounds (VOCs) in human breathe can be used as disease-specific biomarkers for the non-invasive diagnosis of medical conditions, such as acetone for diabetes. Solution-processed bottom gate top contact metal oxide thin-film transistors (TFTs) are used to detect acetone vapours, as part of a proof-of-concept study. The effect of increasing annealing temperature (T) and channel length (L) on electrical and sensing performance are explored. Drain current (Ids) increases following exposure as acetone undergoes a redox reaction with the adsorbed oxygen species on the semiconductor surface, which results in free electrons being released back into the conduction band. Responsivity (R) is maximized at negative bias (Vgs < 0). For L = 50 μm, the peak R of the TFT annealed at 450 °C is three times greater than that of the TFT annealed at 350 °C, with Vgs = − 37.5 V and − 33 V, respectively.