脈衝雷射蒸鍍法製備氧化鈥鋅薄膜的探討：結構、光學與磁性研究

Abstract

利用脈衝雷射沉積法製備摻鈥的氧化鋅薄膜(氧化鈥鋅薄膜)，鈥(Ho)的濃度為0到10%之間，沉積於c指向的藍寶石基板。脈衝雷射功率為2.0 J/cm2 ，鍍膜環境氧氣壓力為3×10^-1 mbar，基板溫度為750 oC。本論文探討氧化鈥鋅薄膜的成份，結構性質，光學性質，磁性以及各種特性間的關聯。 利用XPS能譜進行成分分析，分析薄膜中Ho的濃度。X光繞射光譜中，隨著Ho摻雜濃度越高，薄膜結晶品質越差，c軸晶格常數越小。拉曼光譜中，可觀察到氧化鋅E2-low (99 cm-1)及E2-high (438 cm-1)的振動模式，且在Ho = 3%有螢光效應出現。PL光譜中，分析發光來源為近能隙、鋅空缺、鋅間隙、氧空缺所貢獻。橢圓偏振儀及穿透光譜顯示能隙隨著Ho摻雜比例上升而增加。超導量子干涉磁量儀測定結果顯示室溫及低溫的氧化鈥鋅薄膜皆為順磁性。

Pulsed-laser deposition (PLD) was applied to grow 100nm thick holmium-doped ZnO (Zn1-xHoxO) thin films on c-oriented sapphire substrates under oxygen partial pressure of 3×10^-1 mbar. The nominal Ho concentration ranged from 0 to 10 at.%, temperature of substrate was kept at 750 oC during thin film growth, and the laser energy fluence was 2.0 J/cm2. The composition, structural, optical, and magnetic properties were investigated, and the relation between these properties was discussed.

X-ray photoelectron spectroscopy (XPS) was used for elemental analysis to determine the Ho density in our thin films. X-ray diffraction (XRD) spectra showed decrease in both crystal quality and the c-axis lattice constants of our thin films. Raman-scattering spectra revealed ZnO oscillation mode E2-low (99 cm-1) and E2-high (438 cm-1). For thin film of Ho 3%, fluorescent effect was observed in Raman-scattering spectrum. Photoluminescence (PL) measurements identified near band-edge and defect emissions in the sample, where the major defects are zinc vacancy and zinc interstitials. From ellipsometry and transmittance spectra, the direct band gap of Ho-doped ZnO thin films was found to increase with increasing Ho concentration. Magnetic investigations with a superconducting quantum interference device (SQUID) magnetometer paramagnetism for all Ho-doped ZnO thin films.