氮化鈦氧化薄膜之室溫鐵磁性研究

Abstract

在本論文中，我們使用脈衝雷射沉積法在鈦酸鍶基板上製備氮化鈦薄膜，並在沉積過程中通入不同氧壓以製備不同形式的氧化鈦薄膜。藉由XRD、AFM、XAS的量測來觀察氧化過程中樣品的晶格結構、表面樣貌及電子結構，之後透過SQUID系統量測鐵磁性變化。結果顯示當氧壓大於1x10-4 torr出現鐵磁行為且隨著氧壓的增加鐵磁性行為逐漸變小而最終消失，我們推測鐵磁性來源為氧空缺所造成的。結合XRD、XAS及SQUID的結果，發現室溫鐵磁性與結構的改變有關，結構的改變及混亂將導致氧空缺的產生，使得束縛磁極化子(BMPs)之間的重疊性變高最後產生宏觀鐵磁性。

In this thesis, we have prepared oxidized titanium nitride thin films which were grown on STO(100) substrates by pulsed laser deposition (PLD). The surface morphology of samples with various oxygen pressure was studied by means of atomic force microscopy(AFM). The crystal structures and electronic states were investigated by means of x-ray diffraction(XRD) and x-ray absorption spectroscopy(XAS). The ferromagnetic measurements by means of superconducting quantum interference device(SQUID). The results of SQUID measurements showed room temperature ferromagnetism obviously when oxygen pressure greater than 1x10-4 torr and then disappeared gradually. The results of XRD, XAS and SQUID measurements indicated that the room temperature ferromagnetism changed with structures. The structures change and disorder led oxygen vacancies . Finally, the BMPs overlapped would produce ferromagnetism .