An All Oxide-Based Imperceptible Thin-Film Transistor with Humidity Sensing Properties

• Published in: Materials 2017-05, Vol.10 (5), p.530
• Main Authors: Kim, Kyung Su, Ahn, Cheol Hyoun, Kang, Won Jun, Cho, Sung Woon, Jung, Sung Hyeon, Yoon, Dae Ho, Cho, Hyung Koun
• Format: Article
• Language: English
• Subjects: Amplification; Bending stresses; Bias; Curvature; Degradation; Detection; Electrodes; Mathematical analysis; Oxygen content; Power consumption; Relative humidity; Semiconductor devices; Sensitivity; Sensors; Stresses; Thin film transistors; Threshold voltage; Water vapor
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma10050530

We have examined the effects of oxygen content and thickness in sputtered InSnO (ITO) electrodes, especially for the application of imperceptible amorphous-InGaZnO ( -IGZO) thin-film transistors (TFTs) in humidity sensors. The imperceptible -IGZO TFT with 50-nm ITO electrodes deposited at Ar:O₂ = 29:0.3 exhibited good electrical performances with V of -0.23 V, SS of 0.34 V/dec, µ of 7.86 cm²/V∙s, on/off ratio of 8.8 × 10⁷, and has no degradation for bending stress up to a 3.5-mm curvature. The imperceptible oxide TFT sensors showed the highest sensitivity for the low and wide gate bias of -1~2 V under a wide range of relative humidity (40-90%) at drain voltage 1 V, resulting in low power consumption by the sensors. Exposure to water vapor led to a negative shift in the threshold voltage (or current enhancement), and an increase in relative humidity induced continuous threshold voltage shift. In particular, compared to conventional resistor-type sensors, the imperceptible oxide TFT sensors exhibited extremely high sensitivity from a current amplification of >10³.