Correlation between CO[sub.2] Sensitivity and Channel-Layer Thickness in In[sub.2]O[sub.3] Thin-Film Transistor Gas Sensors

CO[sub.2] monitoring is important for achieving net-zero emissions. Here, we report on a CO[sub.2] gas sensor based on an In[sub.2]O[sub.3] thin-film transistor (TFT), which is expected to realize both low-temperature operation and high sensitivity. The effect of channel thickness on TFT performance is well known; however, its effect on CO[sub.2] sensitivity has not been fully investigated. We fabricated In[sub.2]O[sub.3] TFTs of various thicknesses to evaluate the effect of channel thickness on CO[sub.2] sensitivity. Consequently, TFT gas sensors with thinner channels exhibited higher CO[sub.2] sensitivity. This is because the surface effect is more prominent for a thinner film, suggesting that charge transfer between gas molecules and the channel surface through gas adsorption has a significant impact on changes in the TFT parameters in the subthreshold region. The results showed that the In[sub.2]O[sub.3] TFT in thin channels is a promising candidate for CO[sub.2]-sensitive TFT gas sensors and is useful for understanding an effect of gas adsorption in oxide TFTs with a very thin channel as well.