纖維鋅礦結構氧化鎂鋅的高壓拉曼散射研究

Abstract

本研究利用拉曼頻譜技術來探討鎂原子和外加壓力對氧化鎂鋅(鎂含量介於0 與10莫耳百分比) 之晶格動力學及晶體特性所造成的影響。由於摻雜鎂原子和施以外加壓力對氧化鋅聲子振動行為的改變明顯不同，因此可用來定義具有爭議性的202.7，332.7和511.5 cm-1 聲子振動模。精細的高壓拉曼實驗結果顯示氧化鎂鋅金屬化的相轉變壓力會隨著鎂濃度增加而下降，這個實驗結果是因為鎂導致晶體的離子性和非等向性增加所造成。實驗可測量得到的橫向有效電荷(單原子些微移動所造成的單位位移電偶矩)可用來探討氧化鎂鋅的晶體離子性。此外，我們也分析縱向和橫向光學聲子模的E1-A1聲子分裂，由拉曼技術觀察到的E1-A1聲子分裂情形可以進一步了解氧化鎂鋅的晶體非等向性隨壓力的關係。

This study explores the effects of both Mg and pressure on the lattice dynamics and crystalline properties in Zn1-xMgxO (0 ≦ x ≦ 0.10) using Raman spectroscopy. The incorporation of Mg and the application of external pressure cause distinct phonon vibrational behaviors in ZnO. Accordingly, the 202.7, 332.7, and 511.5 cm-1 phonons, which were controversially assigned, can be defined. Detailed high-pressure Raman results show that the pressure-induced metallic phase transition pressure of Zn1-xMgxO decreases with incresing Mg content. This fact is a consequence of Mg-induced increase in both crystal ionicity and anisotropy. The experimentally measureable transverse effective charge, which is defined as a dipole moment per unit displacement induced by slight movement of an atom, is adopted to trace the crystal ionicity of Zn1-xMgxO. Additionally, the E1-A1 splitting of the longitudinal and transverse optical phonon modes is analyzed which yields insight into the pressure-dependent crystal anisotropy of Zn1-xMgxO via Raman techniques.