反應式濺鍍二氧化釕薄膜之低頻雜訊研究

Abstract

二氧化釕為金屬氧化物且有良好導電性與熱穩定性。由過去研究二氧化釕奈米線之電性量測發現，其電導漲落會隨溫度降低而增大。我們認為電導漲落是來自於金屬氧化物存在二能級系統並導致缺陷移動現象。此篇研究論文，我們利用磁控濺鍍製備不同厚度二氧化釕薄膜，並用X射線繞射分析證實我們樣品存在四角銳鈦礦（Tetragonal rutile）結構。從低溫電性量測中發現在低溫（0.3 K < T < 10 K）的範圍，電阻會隨著溫度降低而增大並呈現良好的自然對數依賴關係。從二維與三維弱局域與電子-電子交互作用對電導修正分析皆發現，其擬合值遠小於我們所量測電阻率。我們猜測可能存在近藤效應(Kondo effect)支配對數依賴關係，來自於電子與二能級系統散射所造成。 為研究二氧化釕二能級系統，我們關注在高溫區的低頻雜訊。我們利用五點法量測，且發現低頻功頻譜密度(Power spectrum density )符合Hooge公式中與樣品偏壓平方成正比的關係。在氧氣退火下我們發現雜訊強度會減小，然而在氬氣退火下雜訊會增加。我們認為是由於氧空缺在氬氣下退火所造成。本篇論文主要利用熱激發模型(Thermal activation model)解釋高溫量測雜訊與二能級系統能障分布的關係。

RuO2 is a metal oxide and has good electrical conductivity and thermal stability. From the previous RuO2 electrical measurement result, the conductance fluctuations would increase as the temperature decrease. We think that the conductance fluctuation result from mobile defect in the two-level-systems (TLSs). In this thesis, we fabricate ruthenium dioxide with different thickness films by magnetron sputtering and we take advantage of X-ray diffraction to confirm the existence of tetragonal rutile structure. From the electrical measurement, we found the rise of the resistance at low temperature (0.3 K < T < 10 K) and reveal strong lnT increment. From two or three dimensional weak localization and electron-electron interaction, we found the fitting value from conductance correction is considerately smaller than we had measured. We think that the existence of the Kondo effect dominates lnT dependence and it origins from the scattering between electron and two-level-systems. In order to study two-level-systems inside RuO2, we concentrated on low frequency noise measurement in high temperature region. We use five probes method to measure noise and found that our power spectrum density is proportional to in Hooge formula. Additionally, we found the noise magnitude would decrease in oxygen annealing, while the noise signal would increase in Argon annealing. We think the existence of oxygen vacancies result from the argon annealing. In this thesis, we mainly use thermal activation model to explain high temperature noise and the relation between TLSs energy distribution.