鐵在紅熒烯/矽(100)上磁性與結構之研究

Abstract

近年來研究指出，鐵磁性材料能受紅熒烯影響晶體結構，而本實驗室近年來研究亦指出鐵磁材料鈷受到紅熒烯介面影響到磁性表現，鐵磁材料鐵受到紅熒烯的影響，產生磁性與結構上的變化，成為本篇研究重點。本研究利用磁光柯爾效應儀、校內合作原子力顯微鏡與磁光柯爾顯微鏡、校外X光繞射與X光電子能譜儀，去探討射頻磁控濺鍍鐵薄膜在蒸鍍成長紅熒烯的系統於矽(100)之上。第一部分在鐵/矽(100)系統中，磁性量測矯頑力隨鐵薄膜厚度增加的變化，矯頑力從25奈米的60 Oe 巨幅上升至30奈米的120 Oe左右，而在鐵約27奈米設為轉變點，並透過X光繞射確認鐵薄膜40奈米以前為bcc結構排列；而在鐵/紅熒烯/矽(100)系統中透過加入不同厚度紅熒烯，觀察上層鐵薄膜的磁性變化，在紅熒烯厚度約1奈米，鐵的矯頑力上升轉變點的厚度提前，當紅熒烯厚度達4、12奈米，矯頑力上升的厚度提前至8奈米，透過X光繞射觀察在加入紅熒烯後發現，鐵薄膜bcc(110)的結晶性上升，其應力增加導致鐵薄膜磁異向能上升使矯頑力增加，而X光電子能譜發現鐵與紅熒烯之間產生介面效應，導致上層鐵薄膜的結構不同；第三部分觀察磁域翻轉模式在鐵薄膜厚度達15奈米以後為大片狀翻轉，在加入紅熒烯時鐵薄膜較薄時呈現細條狀翻轉，鐵薄膜27奈米以後則呈現大片狀翻轉，結合X光繞射分析晶粒大小與原子力顯微鏡分析顆粒在有無加入紅熒烯的不同導致磁域翻轉的變化。In recent years, some research works show that the crystalline structures of ferromagnetic materials can be modified by rubrene additives. Previous studies from our group indicate that magnetic properties of cobalt depends on the preparation method of the Co/rubrene interface. The influence of rubrene on the magnetic properties and crystalline structures of ferromagnetic material iron draws our attentions. In this research work, magneto-optical Kerr effect, magneto-optical Kerr microscope, atomic force microscope, x-ray diffraction and x-ray photoelectron spectroscopy are employed. The RF magnetron sputtering was used to grow iron film and evaporation was used to grow rubrene film in Fe/rubrene/Si(100) systems. In the first part we study magnetic properties of Fe/Si(100). When the thickness of the iron film increases, the coercive force increases from 60 Oe at 25 nm to about 120 Oe at 30 nm. The transform point was around at 27 nm iron. Experimental evidences given by x-ray diffraction show that the iron film is in the bcc structure for iron thinner than 40 nm. In the second part, Fe/rubrene/Si(100) with different rubrene thicknesses are discussed. For the rubrene thickness is 1 nanometer, the thickness of coercive force transform point for iron film is decreased. When the rubrene thickness is 4, 12 nm, the coercivity transform point decreased to 8 nm iron. From XRD measurement, the crystallization of the Fe bcc (110) for the Fe/rubrene film was increased. It results in an increase of the magnetic anisotropy energy for iron film due to increase of stress. Therefore, the coercive force is increased. XPS shown that chemical shift between Fe and rubrene interface are confirmed. Which result in the different of iron film’s crystal structure. In the last part we study the domain reversal mode of iron film. A large domain shape was observed after the thickness of the iron film reach 15 nm. When the rubrene layer is added, the domain tends to be small flake like shape when the thickness of the iron film is thinner than 27 nm. A large domain shape was observed after 27 nm. Combined with XRD studies of grain sizes and AFM studies of particle sizes, the addition of the rubrene result in the different of magnetic domain sizes was observed.