利用同步輻射異常X光散射研究鐵摻雜釔錳氧磊晶薄膜之結構

本論文為利用X光繞射、X光反射率、X光吸收光譜與異常X光繞射量測鐵摻雜之釔錳氧薄膜，以了解其晶體結構，實驗薄膜試樣為脈衝雷射系統成長鐵摻雜之釔錳氧薄膜。 X光繞射與X光反射率實驗是使用國家同步輻射研究中心光束線07A、13A與17B進行實驗，由於同步輻射光源具有高強度、高準直性與光源截面積小等特性，適合來進行結構分析與φ-scan的軸向定位去了解薄膜之成長，X光反射率配合GenX分析軟體來模擬薄膜厚度、粗糙度與結構排列之資訊。由於錳原子與鐵原子的散射因子相當接近，一般X光繞射無法分辨這兩個原子在結構特定位置對繞射峰強度產生的影響，運用異常繞射可以由禁制峰獲得本樣品具有雙鈣鈦結構之序化情形。本實驗利用同步輻射光源之能量可調性，在光束線17B把能量調至Mn的K吸收邊(6.539 keV)與Fe的K吸收邊(7.112 keV)改變入射能量，做異常X光繞射量測光強度，並與X光繞射和X光吸收光譜(光束線16A)比較，經由Kramers-Kronig 關係式求得散射因子，並與繞射峰強度變化做比較。發現半鐵摻雜的釔錳鐵氧YMFO薄膜有兩相存在，兩晶胞單位體積一樣，調變能量在錳與鐵吸收邊緣時，繞射光強度皆有明顯下降之趨勢，兩者下降趨勢相同，其成分比例皆為YMn0.5Fe0.5O3，然而YMFO(010)禁制峰沒有繞射光強度，為非有序結構。另一個樣品是YMFO舊樣品為單一相，調變能量在錳與鐵吸收邊緣時，YMFO(010)禁制峰繞射光強度有顯著變化，其光強度變化約有15至20倍，為有序結構。

關鍵字

多鐵材料；同步輻射光源；異常X光散射；磊晶結構

並列摘要

In this work, the crystal structure and electronic property of the orthorhombic YMnO3 epitaxial film on YAlO3(010) substrate and Fe-doped YMnO_3 epitaxial film were studied by using X-ray diffraction (XRD), X-ray reflectivity (XRR), X-ray absorption spectroscopy (XAS) and anomalous X-ray diffraction. X-ray diffraction and X-ray reflectivity were measured at beamline BL07A, BL13A and BL17B in National Synchrotron Radiation Research Center (NSRRC). Due to the synchrotron radiation source has high intensity, excellent collimation and low emittance, those are suitable for analyzing the crystal structure and growth of the films. The thickness, roughness and arrangement of the films from X-ray reflectivity were analyzed by using GenX program. Because of the very similar scattering factors of Mn and Fe atoms, it is hard to distinguish these two atoms at specific sites of the structure from the change of diffraction peak intensity. Anomalous X-ray scattering was used to study the problem of the diffraction peak splitting of Fe-doped YMnO3 epitaxial film in (020) plane. The anomalous X-ray diffraction was performed at BL17B and XAS at BL16A. We change the incident X-ray energy to Mn K-edge (6.539 keV) and Fe K-edge (7.112 keV), then measure the (020) diffraction peak intensity. By comparing the anomalous X-ray diffraction with XAS, we calculate the scattering factor by using Kramers-Kronig relation. We found that the YMFO new sample had two phase and disorder structure. Another sample was YMFO old sample which was single phase. When we change the incident X-ray energy to Mn K-edge and Fe K-edge, the YMFO(010) forbidden diffraction intensity was enhanced 15 times to 20 times. The YMFO old sample was order structure.

並列關鍵字

Multiferroic ； Synchrotron Radiation Light Source ； Anomalous x-ray scattering ； Epitaxial structure

參考文獻

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利用同步輻射異常X光散射研究鐵摻雜釔錳氧磊晶薄膜之結構

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