Effect of Ultraviolet Light on Mn₃O₄ Thin Films that are Grown Using SILAR for Room-Temperature Ozone Gas Sensors

Abstract

Successive ionic layer adsorption and reaction (SILAR) is a promising technique to fabricate gas sensors at room temperature. However, the quality of the films is poor, leading to reduced surface area and increased defects within the film structure, thus decreasing the overall gas response. Inferior film quality also negatively affects the stability and reproducibility of the gas sensors over time. This study determines the effect of UV treatment on the structural, morphological, and ozone (O3) gas-sensing properties of p-type Mn3O4 thin films. As UV treatment time increases, the O3 gas-sensing characteristics increase because a porous structure with a higher surface area is formed and electrical conductivity is increased. Under a UV intensity of 20 mW cm−2, the Mn3O4 sensor exhibits gas response, response time, and recovery time of 1.62, 58, and 39 s, respectively, against 5 ppm concentration of O3 gas. Moreover, the Mn3O4 gas sensor exhibits excellent long-term stability showing around 3% variation in gas response over 60 days. This strategy allows the deposition of high-quality p-type Mn3O4 thin films using SILAR for applications in flexible gas sensors.

Self-Powered InGaZnO Ozone Gas Sensors Based on a Metal–Semiconductor–Metal Structure with Asymmetric Interdigitated Electrodes

“…However, an applied external voltage is required for the separation of electron–hole pairs, given the symmetrical structure of the device . Recent efforts are increasingly focused on the light-activated gas sensors because of their remarkable effectiveness in enhancing gas-sensing performance at room temperature. − To supply the activation energy for gas reactions, an ultraviolet (UV) light-emitting diode (LED) is employed. This approach raises the question of whether UV illumination can induce a photovoltage within the planar MSM structure, similar to the case in the vertical p–n structure.…”