本研究利用射頻磁控濺鍍法，在不同氣氛下濺鍍出n型及p型鐵酸鉍，並將兩種型態堆疊形成多層膜p-n異質接面進行後續光伏特以及光催化性質量測。在本實驗中選用亞甲基藍作為示範汙染物，驗證p-n 異質接面在光降解方面上的實際效果。實驗結果利用XRD證明試片為純相鐵酸鉍，並藉由SEM看出表面為緻密的結構表現；透過XPS及Mott-Schottky瞭解n型及p型鐵酸鉍的差異，並利用UV-vis、UPS技術來精準畫出能帶的位置，了解載子在不同薄膜層之間的傳輸機制。
根據實驗結果，n型及p型鐵酸鉍皆存在氧空缺，而p型的氧空缺數量較多。其中n型鐵酸鉍的載子源自於電中性的氧空缺，使其可以作為電子的供給；p型的載子源自於帶正電的氧空缺，使其可以接收電子。兩者的能隙也略有不同，n型的能隙為2.57 eV，略高於p型的2.5 eV。進一步將兩者堆疊為p-n junction之後，光降解效率在兩個小時之後來到95%以上，有顯著的提升。在透過Mn、Mg摻雜之後，能隙進一步縮小至1.83 eV，並延伸異質接面的特性，將摻雜之鐵酸鉍濺鍍在載子傳導層WO3以及TiO2上協助載子分離，在光伏特性質上提升開路電壓以及短路電流。

BiFeO3 (BFO) thin films were deposited on LaNiO3 (LNO) buffered glass substrates by RF magnetron sputtering under different conditions to obtain either n or p type films. A BFO p-n junction could therefore be fabricated to enhance photovoltaic and photocatalytic properties. Both types of BFO films contained oxygen vacancies with p-type films having a higher number of the vacancies. The carriers in p-type BFO were correlated to the positively charged oxygen vacancies that have no trapped electrons, whereas the carriers in n-type BFO were correlated to neutral oxygen vacancies that have two trapped electrons. BFO were then co-doped by Mn and Mg (BFMMO) to reduce band gap, which was measured to be 1.83 eV, much lower than that of undoped BFO (~2.5 eV). The construction of bilayer BFO p-n junction led to great improvement in photodegradation of methylene blue (MB), with over 95% MB being degraded in 120 minutes. A better performance was achieved with the p-n junction constructed with BFMMO, which degraded over 95% MB in just 90 minutes. WO3 and TiO2 were deposited on LNO electrode as carrier transport layer (CTL). The band alignments between BFMMO and WO3 or TiO2 were determined by ultraviolet photoelectron spectroscopy, which revealed that only WO3 may act as an effective CTL. Indeed, BFMMO/WO3/LNO multilayer showed an improved photovoltaic output under light illumination, and its open-circuit voltage and close-circuit current were switchable by the electric polling directions.

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