氧化鎵在高溫下穩定且具有半導體的特性，近年來最常被應用於感測還原性氣體。本研究利用真空蒸鍍熱氧化法製備氧化鎵薄膜氣體感測器。以多層膜的製備方式在石英基板上先製備緻密的底層氧化鎵薄膜，最後再分別蒸鍍上三種不同最外層鎵薄膜厚度(0.2, 0.4, 1μm)，除了最外層鎵薄膜厚度的變因之外，還有在不同氧化氣氛環境下進行高溫氧化；針對這兩種變因探討在氧化鎵薄膜上奈米線結構的生長情形，以及對氧化鎵薄膜感測性的探討。
　　實驗結果顯示，Ga與石英基板間具有良好的親和性，因此初期成長階段呈現一扁平液滴的型態。當鎵薄膜增加至280nm時會出現”balls-on-ball”之型態。製作底層緻密氧化鎵薄膜時，為了避免奈米線的產生，需要將氧化系統保持在純氧的環境下，且採用多層膜的製備方式，此舉除了可以增加鎵薄膜的比表面積並可避免較厚的薄膜產生奈米線的結構。氧化鎵薄膜上奈米線(nanowire)形成的條件主要有兩點：(1) 膜厚要達到一定的厚度才會有明顯的奈米線產生；(2) 在低濃度的氧氣氣氛下較易促進氧化鎵奈米線的成長。最外層鎵薄膜厚度為1μm在無氣體流動的氧化條件下所成長的奈米線長度較長，而鎵薄膜上奈米線結構緻密度最高的氧化條件為空氣與氮氣的混合(氧濃度較低的環境下)。本實驗對氧化鎵薄膜所作的感測性實驗，全部以P型半導體的電阻變化呈現。最外層鎵薄膜厚度為0.2μm與1μm之氧化鎵，於四種不同溫度感測3000ppm酒精，在感測溫度為500℃時的靈敏度最佳，不過其回復時間卻過長，而當感測溫度升高時的靈敏度驟降。理論上來說，感測氣體濃度越高，其電阻變化也會越明顯，不過本實驗製備之奈米線氧化鎵薄膜卻呈現出與理論結果相反的現象。

　　Ga2O3 possesses the semiconductor characteristic is stable at high temperature, and has been applied in detecting reducing gas recently. In the current study, Ga2O3 semiconductor thin film was prepared by rtheotaxial growth and thermal oxidation (RGTO) method on SiO2 substrates. Multilayer growth technique was used to prepare the compact gallium oxide bottom thin film. The morphology and the electrical properties of the Ga and Ga2O3 films were measured as functions of the thickness of final Ga film deposited over the compact Ga2O3 bottom thin film and the atmosphere of oxidation. Their effects on the growth of nanowires of the Ga2O3 were examined.
　　The experimental results show that there is a good wettability between gallium and SiO2 substrates, as a result, a flat drops are observed morphology during the initial period. A “ball-on-ball” type morphology appears as the thickness of film exceeds 280nm. In order to avoid growing nanowires of Ga2O3 on initial thin film, the oxidation process has to be carried out under pure O2 atmosphere. Multilayer growth technique leads to an increase in the surface area of thin film and an inhibition of nanowires growth for thicker films. There are two necessary requirements for the formation of nanowires: (1) The Ga film must be thick enough and (2) A low O2 concentration promotes the growth of Ga2O3 nanowires. When the oxidation of 1μm Ga film is carried out under rest air, longer nanowires are produced, however highest density of nanowires is observed if the oxidation is carried out under a mixture of air and nitrogen. In the study the resultant Ga2O3 possesses a P-type semiconductor characteristic. The sensitivity of the Ga2O3 films in response to ethanol were found to have an optimum sensing temperature at 500℃, but it’s recovery time was too long, and the sensitivity of the Ga2O3 films decrease with the temperature. Theoretically, an increase of concentration of reactant vapor, must lead to more shifting of the resistance, but a discrepancy results was observed in this study.

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