近年來應用半導體薄膜於氣體感測上的使用非常廣泛，其主要感測機制乃是利用半導體薄膜在不同氣體下其導電性質不同所致，而由感測器電阻值的變化可求得其對氣體之感測度。
本研究以物理氣相共蒸鍍法在氧化鋁基板上共蒸鍍鋅、銦薄膜，配合貴金屬鈀的混合摻雜及熱氧化法製備半導體式薄膜氣體感測器，並藉由SEM、XRD分析其薄膜之型態及組成，再以酒精與一氧化碳氣體作為感測氣體進行相關感測性質的量測。試著探討半導體式氣體感測器之感測機制及在不同蒸度速率、不同原子比例、不同操作溫度及摻雜貴金屬鈀時對感測性質之影響。
由實驗結果顯示：1. 氧氣在感測機制中扮演相當重要之角色，當溫度較高時（T＞500K），氧氣會與半導體內之電子形成氧離子（O-）吸附，使得感測器電阻升高；而當還原性感測氣體通入時會與所吸附之氧反應，而降低感測器之電阻。2. 在相同條件下對酒精比對一氧化碳具有更高的感測度。3. 對於酒精與一氧化碳各存在一最佳感測溫度，分別為3500C與4500C。4. 蒸鍍速率較快時，所得之薄膜表面晶粒粒徑較大，其感測性值較差。 5. 對不同原子比例之感測器薄膜當蒸度速率相同時，其表面型態類似，對酒精與一氧化碳之感測度分別以鋅銦兩成分在鋅佔42.3 at %與72.6 at %時有最佳感測值。6. 混合法摻雜鈀時，其感測度皆下降，但會隨摻雜量增加而有回升之趨勢。7. 對酒精而言摻雜鈀時其應答及回覆時間都有下降之趨勢，而對一氧化碳氣體則無。8. 摻雜鈀時其最佳操作溫度有下降之趨勢，而隨著操作溫度的升高其應答與回覆時間都有所短的情形。

Thin-film semiconductor is extensively used as gas sensor to detect poison gas, in recent years. The major sensing mechanism of semiconductor gas sensor is base on the change of electrical properties with gas composition, the gas sensitivity in response to the reacting gas is calculated to the change of the for the electrical properties.
In the paper, the ZnO and In2O3 thin films doped with Pd were prepared by vacuum co-deposition of zinc and indium on Al2O3 substrate followed with thermal annealing and oxidation. The thin film morphology and composition was analyzed using SEM and XRD. In the study the sensing mechanism of thin-film semiconductor gas sensor was examined, and the sensing properties for CO and ethanol gas were measured.
The experimental results show that (1) the oxygen gas play an important role in the sensing mechanism, as temperature increases up to 500k, the adsorbed oxygen on the sensor surface dissociates and forms O-, where electron is extracted from semiconductor leading to an increase in the resistance. When exposing to reduce gas, the reduce gas reacts with adsorbed O-, and the electron is released to the semiconductor, resulting in a decrease in the resistance. (2) The sensor has a higher sensitivity to ethanol than that to CO in the same conditions. (3) The sensor has an optimum sensitivity at 3500C and 4500C for ethanol and CO, respectively. (4) Larger grain sizes produced at higher deposition rate, that the lower sensitivity was obtained. (5)No obvious change in surface morphology with atomic ratio at the same deposition rate. The optimum sensitivity is response to ethanol and CO at Zn 42.3 at%, 72.6 at% in the sensor with Zn-In binary component. (6) When doped with Pd, the sensitivity decreases, but recovers as the doped amount increase further. (7) Doping of Pd leads to a decrease in response time and recover time for detecting ethanol but no change for CO. (8) The optimum temperature decreases with the doping of Pd, and the response and recover time decrease with increasing temperature.

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