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

Abstract

We have examined the effects of oxygen content and thickness in sputtered InSnO (ITO) electrodes, especially for the application of imperceptible amorphous-InGaZnO (a-IGZO) thin-film transistors (TFTs) in humidity sensors. The imperceptible a-IGZO TFT with 50-nm ITO electrodes deposited at Ar:O2 = 29:0.3 exhibited good electrical performances with Vth of −0.23 V, SS of 0.34 V/dec, µFE 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.

The Effect of Zirconium Doping on Solution-Processed Indium Oxide Thin Films Measured by a Novel Nondestructive Testing Method (Microwave Photoconductivity Decay)

“…Indium oxide (In 2 O 3 ) films have high electron mobility, high carrier density, and excellent optical transmittance compared with other oxide semiconductors [17,18], making them an ideal material for transparent thin film transistors [19]. In order to obtain high-quality In 2 O 3 films, other elements are added, such as InSnO (ISO) [20][21][22], InZnSnO (IZTO) [23][24][25][26], InGaZnO (IGZO) [27][28][29][30], etc. The Zr element has a strong binding capacity to oxygen (Zr-O: 776 KJ/mol), higher than that of the In element to oxygen (In-O: 348 KJ/mol), which can inhibit the formation of oxygen vacancies.…”

Effect of Simultaneous Mechanical and Electrical Stress on the Electrical Performance of Flexible In-Ga-Zn-O Thin-Film Transistors

“…Indium-gallium-zinc oxide (IGZO) thin-film transistor (TFT) is being widely used for the backplane of large-area active-matrix organic-light-emitting diode displays, owing to its excellent properties including high field-effect mobility ( μ FE ), low-off current, high uniformity, and low process temperature [1,2,3,4,5,6,7,8,9,10,11]. Recently, there is increasing interest in the application of IGZO TFTs in demonstrating the active-matrix backplane for flexible displays [12,13,14,15,16].…”

Drain Current Stress-Induced Instability in Amorphous InGaZnO Thin-Film Transistors with Different Active Layer Thicknesses

“…Recently, amorphous indium gallium zinc oxide (a-IGZO), as a representative of an amorphous metal oxide-based semiconductor, has been widely investigated for use in the active layer of thin-film transistors (TFTs) due to its high electron mobility, good transparency in visible light, chemical and thermal stability, low temperature processing, and smooth surface [ 1 , 2 , 3 , 4 ]. The a-IGZO TFT with excellent electrical properties, such as high mobility ( μ ) of over 10 cm 2 ·V −1 ·s −1 and low values of subthreshold swing, has become one of the research hotspots for the advanced display application in next-generation active-matrix liquid crystal displays (AM-LCDs) and active-matrix organic light-emitting diodes (AM-OLEDs) [ 5 , 6 , 7 , 8 ]. Hitherto, AM-OLEDs driven by the a-IGZO TFTs involve two or three transistors and one capacitor current-biased voltage-programmed pixel circuit.…”