We suggest the use of a thin-film transistor (TFT) composed of amorphous InGaZnO (a-IGZO) as a channel and a sensing layer for low-concentration NO₂ gas detection. Although amorphous oxide layers have a restricted surface area when reacting with NO₂ gas, such TFT sensors have incomparable advantages in the aspects of electrical stability, large-scale uniformity, and the possibility of miniaturization. The a-IGZO thin films do not possess typical reactive sites and grain boundaries, so that the variation in drain current of the TFTs strictly originates from oxidation reaction between channel surface and NO₂ gas. Especially, the sensing data obtained from the variation rate of drain current makes it possible to monitor efficiently and quickly the variation of the NO₂ concentration. Interestingly, we found that enhancement-mode TFT (EM-TFT) allows discrimination of the drain current variation rate at NO₂ concentrations ≤10 ppm, whereas a depletion-mode TFT is adequate for discriminating NO₂ concentrations ≥10 ppm. This discrepancy is attributed to the ratio of charge carriers contributing to gas capture with respect to total carriers. This capacity for the excellent detection of low-concentration NO₂ gas can be realized through (i) three-terminal TFT gas sensors using amorphous oxide, (ii) measurement of the drain current variation rate for high selectivity, and (iii) an EM mode driven by tuning the electrical conductivity of channel layers.

中文翻译：

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面向低浓度气体检测的非晶氧化物薄膜晶体管的充分工作

我们建议使用由非晶InGaZnO（a-IGZO）组成的薄膜晶体管（TFT）作为通道和用于低浓度NO ₂气体检测的传感层。尽管非晶氧化物层在与NO ₂气体反应时具有受限的表面积，但是这种TFT传感器在电稳定性，大规模均匀性和小型化的可能性方面具有无与伦比的优点。a-IGZO薄膜不具有典型的反应位点和晶界，因此TFT的漏极电流变化严格地源于沟道表面与NO ₂之间的氧化反应气体。特别地，从漏极电流的变化率获得的感测数据使得可以有效且快速地监视NO ₂浓度的变化。有趣的是，我们发现增强型TFT（EM-TFT）可以区分NO ₂浓度≤10 ppm时的漏极电流变化率，而耗尽型TFT足以区分≥10 ppm的NO ₂浓度。该差异归因于有助于气体捕获的电荷载流子相对于总载流子的比率。具有出色检测低浓度NO _2的能力 可以通过（i）使用无定形氧化物的三端TFT气体传感器，（ii）测量漏极电流变化率以实现高选择性以及（iii）通过调整沟道层的电导率驱动的EM模式来实现这种气体。