超薄氧化鈷膜在銥(111)表面上的製備與物性探討

Abstract

本論文內容將探討Co/CoO/Ir(111)超薄膜的薄膜成長與組成、表面磁性以及薄膜表面結構變化，並利用歐傑電子能譜儀、深度組成分析、表面磁光柯爾效應、低能量電子繞射等方法進行上述的研究。從薄膜成長與深度組成分析得知，在一定層數下的CoO會形成良好的化合狀態；將薄膜進行熱退火步驟後，O與Co的歐傑電子訊號比值會下降。CoO/Ir(111)超薄膜表面鍍上Co後，形成Co/CoO介面，零場冷卻後利用表面磁光柯爾效應儀測量磁滯曲線，發現隨著溫度的降低，矯頑力有增加的趨勢，但磁滯曲線呈現對稱的情況；在場冷卻下的表面磁性分析中，發現除了矯頑力增加，並且有交換偏移現象發生；從薄膜表面結構的觀察中，顯示出其結構週期性變強。經由系列化研究超薄膜系統在不同膜厚下的行為，可以得到鐵磁層與反鐵磁層間交換耦合的最佳條件。

The fabrications of Co/CoO/Ir(111) ultrathin films and their properties have studied using Auger electron spectroscopy (AES), depth profiling, surface magneto-optic Kerr effect (SMOKE) and low-energy electron diffraction (LEED) techniques. From the analysis of growth mode and depth profiling, CoO/Ir(111) shows good compositional quality. After annealing treatments, Auger signal ratio of O/Co decreases which results from desorption of fractional oxygen. The Co/CoO interface is formed after post-deposition of Co overlayer on CoO/Ir(111). Both enhancement of coercivity and shift of hysteresis loop were observed after cooling the specimens in a magnetic filed. These evidences show the formation of exchange bias interfaces. In addition the periodic ordering is stronger as revealed from the LEED measurements. From the systematical investigations, the optimal condition for the formation of strong exchange bias in the Co/CoO/Ir(111) system is achieved.