利用遠場二倍頻及時間解析近場顯微鏡研究鉍鐵氧薄膜

Abstract

在本論文中，首先利用波長800 nm的飛秒脈衝在不同軸向之鉍鐵氧薄膜上產生遠場二倍頻信號，觀察其對稱性與鐵電極化方向之關係。另外，利用自組式近場光學顯微儀，量測鉍鐵氧-鈷鐵氧奈米結構薄膜的二倍頻訊號，並與壓電力顯微鏡所得到的結果做了比較。綜合遠場及近場二倍頻信號，進一步分析鉍鐵氧薄膜二倍頻信號的來源。透過與光激發探測系統的結合，我們完成了時間解析近場光學顯微儀，利用近場時析光譜對鉍鐵氧薄膜的鐵電疇域做了初步的實驗及探討。

In this thesis, we measure the far-field second harmonic generation (SHG) in various-oriented BiFeO3 thin films by femtosecond laser pulses with 800 nm. From the symmetry of SHG pattern, we could analyze the relationship between the SHG and the polarization in BiFeO3. Moreover, the SHG in the BiFeO3-CoFe2O4 nanostructure samples can be measured by a home-made Scanning Near-field Optic Microscopy (SNOM). By comparing the results of SNOM and PFM, the mechanism of SHG in BiFeO3 thin films could be further revealed. Finally, the time-resolved SNOM has been performed here to study the ferroelectric domain in BiFeO3 thin films.