本實驗主要在探討不同厚度下使用摻雜原子百分比5% 鈣(Ca)離子濃度鐵酸鉍(BiFeO3, BFO)薄膜所表現出的光伏效應，藉由各項儀器來觀察BFO薄膜的差異性，來推測影響光伏效應的可能原因與機制。
本實驗以磁控濺鍍法(RF-sputter)成長BFO薄膜以及上下電極於矽基板Si(100)上。利用場發射電子顯微鏡來觀察厚度是否符合實驗所設定，X光繞射儀來分析薄膜的結晶特性，X光反射儀與原子力顯微鏡觀察粗糙度，鐵電量測儀量測電滯曲線，使用405nm Laser量測光伏效應。
由BFO薄膜的XRD圖譜僅發現BFO ( 0 0 1) 與(0 0 2) 繞射峰，可知BFO薄膜具有良好的結晶性及明確的優選方位。由XRD圖譜也看出，隨著厚度增加，薄膜有應力釋放的現象。光反射儀與原子力顯微鏡結果顯示隨著厚度增加粗糙度也跟著變化，但是變化不大。電滯曲線的結果顯示，隨厚度的增加，薄膜的極化值有下降的趨勢。同時，光伏效應亦隨著膜厚增加而逐漸降低。當應力產生變化，晶格變形量改變，將導致偶極矩改變，影響薄膜內電場，致使效率明顯改變。此外，當厚度增加至100及150奈米時，上下電極間距大幅拉長，致使電子收集效率降低，以及正負電荷對在薄膜中移動時發生再結合或是散射現象機率提升，掩蓋薄膜光伏效應的呈現。

In this experiment, the photovoltaic effect with different film thickness of 5% Ca doped BiFeO3 thin films were investigated. The probable physical mechanism were carried out many different measurements which may affect the efficiency of the photovoltaic effect. The specimen of BFO thin films and the electrode were all deposited on Si(100) by RF magnetron sputtering. First, we grew LaNiO3 on Si(100) at 450 . Second, The 5% Ca doped BiFeO3 films were deposited on LaNiO3. Third, we deposited Pt or AZO to do measurements, respectively. Film thickness was estimated by SEM and X-ray reflectivity. Film crystallinity was carried out by X-ray diffraction measurement. The morphology was measured by atomic force microscope and X-ray reflectivity. The hysteresis loop was performed by TF-2000 and the photovoltaic effect were measured by 405 nm laser.
BFO was (100) highly preferred along Si (100) substrate from X-ray diffraction measurement. BFO film strain relax as film thickness increase, hence the diffraction peak position shift more close to the expected bulk value. The surface roughness, which was carried out by AFM and X-ray reflectivity has little increase as film thickness thicker. The hysteresis loop showed that the polarization slow down as the film thickness increased. The photovoltaic effect also slow down as the film thicker.
The BFO built-in electric field affect the efficiency of photovoltaic effect. As the film thickness increased to 100 nm, the strain relax caused built-in electric field become weaker and the probability of electron and hole recombined increase due to distance between two electrode; therefore, the efficiency of photovoltaic hidden.

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