鉍銅硒氧(BiCuSeO)為P型半導體，擁有特殊的層狀結構，由絕緣層(Bi2O2)2+與導電層(Cu2Se2)2-沿C軸相互交疊而成，此結構造就了鉍銅硒氧的高導電率與低熱傳導係數，被廣泛研究作為熱電材料之用。另一方面，鉍銅硒氧在鍍膜環境(即高真空低氧分壓)下可以穩定存在，且其晶格常數與常見的氧化物基板鈦酸鍶(SrTiO3)有極佳的匹配度，所以非常適合作為氧化物薄膜元件之底電極材料。但是鉍銅硒氧中的Se和Bi容易揮發，造成熱穩定性較差，給後續薄膜成長帶來困難。先前塊材研究發現摻雜Ga可以提升熱穩定性，所以本研究期望以射頻磁控濺鍍法於鈦酸鍶(100)單晶基板上成長摻鎵之鉍銅硒氧(BiCu0.95Ga0.05SeO)薄膜，控制基板溫度以及鍍率(檔板開關時間)等製程參數，探討其對於薄膜結晶特性以及熱穩定性的影響。
摻鎵之鉍銅硒氧薄膜的XRD結果顯示，隨著檔板關閉時間減短，出現BiSe雜相的繞射訊號，表示BiSe在較快的濺鍍速率下較容易生成；隨著檔板關閉時間增加，可以大幅度的降低甚至去除BiSe二次相。由此可知本研究成功以射頻磁控濺鍍法製備出單相的摻鎵鉍銅硒氧薄膜。此外，於較低的基板溫度下(300 oC、350 oC)，由XRD繞射結果可以觀察到所成長的摻鎵鉍銅硒氧具有(001)的擇優取向，成長溫度350 oC時由二次電子影像可以觀察到立方顆粒的結晶。在高溫(>400 oC)的基板溫度，則是觀察到具有(102)擇優取向的摻鎵鉍銅硒氧薄膜，並且其二次電子影像結果顯示表面結晶呈現平片狀。
另一方面，為探討摻鎵鉍銅硒氧薄膜的熱穩定性，本研究初步嘗試以連續製程製備鈦酸鍶/摻鎵之鉍銅硒氧/鐵酸鉍的雙層膜結構。在基板溫度為500 oC的製程參數下，XRD結果仍然可以觀察到鉍銅硒氧的繞射訊號，但隨著濺鍍時間增加，鉍銅硒氧繞射強度降低。此外，本實驗室先前的研究結果顯示，在高溫的連續製程中，鉍銅硒氧會完全被分解，因此，與純鉍銅硒氧相比，摻雜鎵確實提升鉍銅硒氧薄膜的熱穩定性，但因其並未阻止鉍的揮發，故效果仍有限。

In this research, we attempted to grow epitaxial BiCu0.95Ga0.05SeO (BCSO:Ga) thin films on SrTiO¬3(100) single crystal substrates for applications as the bottom electrode on the popular substrate SrTiO3. The films were grown by RF magnetron sputtering method. The Ga doping effects on the film growth of BiCuSeO and its thermal stability were investigated.
The results of BCSO:Ga films show that as the shutter closing time decreases, the BiSe heterophase appears. As the shutter closing time increases, the BiSe heterophase can be removed. A single-phase BCSO:Ga thin film was successfully grown by RF magnetron sputtering method in this research. In addition, we can observe the BCSO:Ga thin films have (001) preferred orientation at a lower substrate temperature (300 oC, 350 oC). Secondary electron images can observe the cubic crystal at 350 oC.
In order to investigate the thermal stability of BCSO:Ga thin films, a continuous process was used to prepare SrTiO3 substrate/BCSO:Ga/BiFeO3(BFO) films structure. Under the substrate temperature of 500 oC, the results can still observe the BCSO:Ga films. As the sputtering time increases, the intensity of BCSO:Ga diffraction signal decreases. Comparing with pure BCSO thin films, BCSO:Ga thin films indeed improve its thermal stability. But, it does not prevent the volatilization of Bi, the effect is still limited.

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