本研究目標為探討鐵摻雜對於鉍銅硒氧塊材的物理性質影響以及希望可以經由射頻磁控濺鍍系統在(001)鈦酸鍶單晶基板上成長出具有高熱穩定性及高化學穩定性的鐵摻雜鉍銅硒氧磊晶薄膜。
本實驗室曾經以射頻磁控濺鍍法成功在(001)鈦酸鍶基單晶基板上磊晶成長鉍銅硒氧以作底電極之用，但由於鉍銅鍶氧中的鉍元素跟鍶元素有較高的蒸氣壓會容易揮發導致鉍銅鍶氧在高溫環境會分解，以及在後續濺鍍功能性氧化物鐵酸鉍時會與鐵酸鉍層發生反應並且分解。有見及此，參考本實驗室以往在鐵硒超導體中，鐵的加入可以和硒產生鍵結並有效抑制硒的揮發。故希望鐵摻雜可以有效改善鉍銅硒氧中硒元素的揮發以提高鉍銅硒氧的熱穩定性及化學穩定性，從而在更高的基板溫度下磊晶成長鉍銅硒氧薄膜。
本實驗使用固相燒結法制備磁控濺鍍用之靶材，並且對其作結構，成分，電性，以及熱重分析。XRD結果顯示鐵摻雜到5%為止都没有偵測到有二次相的生成而且成份都没有明顯的偏離，而其席貝克系數反映出隨著鐵摻雜濃度上升，鉍銅硒氧的濃度會隨之上升。在薄膜成長方面，本實驗使用鐵摻雜量為1% 的鉍銅硒氧作為濺鍍用的靶材並利用檔板的設置以降低有效鍍率並在基板溫度為450C 下濺鍍30分鐘可以成功磊晶成長鉍銅硒氧於(001)鈦酸鍶單晶基板上。磊晶鉍銅鍶氧薄膜的載子濃度為4.99×1020/cm3, 指出摻鐵後的磊晶鉍銅鍶氧薄膜為p-型半導體。

The goal of this research is to investigate the influence of Fe doping on the thermal stability and epitaxial film growth of BiCuSeO via RF magnetron sputtering system. Bi-CuSeO has the tetragonal crystal structure with the space group of P4/nmm and the lattice parameters of a=b=3.9273 and c=8.9293. Although this material has been studied inten-sively for thermoelectric application, the current work is intended to develop it as a bot-tom electrode on the popular substrate SrTiO3 because of the small lattice misfit. There were two main parts in this research. In the first part, the influence of Fe doping in Bi-CuSeO was investigated using the bulk samples synthesized by sintering in flowing Ar atmosphere, in order to decide the optimal Fe concentration for the sputtering target. The phase purity of variously doped samples was examined by X-ray diffraction (XRD). The morphology and composition were studied by scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS). The thermal stability was char-acterized by thermogravimetric analysis (TGA). The Seebeck coefficient and electric conductivity were measured to confirm that they were not degraded significantly by the Fe doping. For the second part, the focus of the study was on the growth, structural analy-sis and electric properties of epitaxial thin films of the Fe-doped BiCuSeO. After a series of experiments with varied substrate temperatures, BiCuSeO:1%Fe epitaxial films were successfully grown on (001) SrTiO3 substrates at 450 C. High precision XRD measure-ments showed that the epitaxial films had a out-of-plane texture of 0.61 and in-plane texture of 2. SEM showed that the films were dense with a smooth surface suitable for subsequent film growth. Hall-effect measurements indicated that the Fe doped films kept the same p-type conductivity as the pristine BiCuSeO with the carrier concentration being 4.99×1020/cm3 at room temperature, which may be high enough as the bottom electrode.

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