探索準一維氧化鋅奈米線電性傳輸

Abstract

熱蒸鍍鈦金電極時由於真空條件影響，鈦金接面處有氧化鈦產生，而氧化鈦為一種半導體材料，與金的功函數不匹配，所以此類元件接點為蕭特基接觸。然而蕭特基接面處具有一個空乏區，空乏區內的電場會壓縮氧化鋅奈米線通道，使得電性傳輸別於氧化鋅奈米線本質特性。 本實驗為了研究本質與電場壓縮下氧化鋅奈米線元件，我們製成三種元件：typeⅠ元件電極為雙邊歐姆接觸，用來研究本質氧化鋅奈米線電性傳輸；typeⅡ元件是在熱蒸鍍電極時，通入氧氣使接點為蕭特基接觸；typeⅢ元件先製作一個歐姆接觸的氧化鋅奈米線元件，利用第二次製成在源極與汲極中間蓋上一個鉑電極，製成一個電場壓縮氧化鋅奈米線通道元件。利用typeⅠ元件確定本質氧化鋅奈米線電性傳輸，電性傳輸可以完全由熱活化傳輸與三維變程跳躍傳輸電導疊加模型解釋。利用typeⅡ元件與typeⅢ元件來確定電場壓縮奈米線通道的電性傳輸，此類電場壓縮奈米線通道元件電性傳輸遵循拉廷格液體理論特性：電阻與溫度、電流與電壓呈現冪次關係，即 與 ，以及實驗數據以I/T1+α與eV/kBT作圖會崩潰至同一曲線上，即歸一曲線。分析此類電場壓縮奈米線通道元件的室溫電阻與拉廷格參數 、 與 關係圖時，發現typeⅡ元件趨勢並不符合理論預測，因此我們推論電場壓縮下氧化鋅奈米線元件電性傳輸並非單純由拉廷格液體所貢獻，typeⅡ元件電性傳輸由接點電阻串聯準一維奈米線主導。此外，typeⅢ元件電性傳輸特性符合拉廷格液體理論，且藉由拉廷格液體所擬合參數與室溫電阻趨勢也符合理論預測，由此推論此類元件為準一維奈米線電性傳輸所主導。

When a metal makes contact with a semiconductor, depletion is shall form spontaneously at this metal/semiconductor (M/S) interface, resulting in a Schottky barrier. In this study, we attempted to utilize M/S contact to build up an electrical field and to deplete the conducting channel in survey of quasi-one-dimensional electron transport in a single ZnO nanowire. High quality ZnO nanowires with a small deviation and an average diameter of ~50 nm are selected for fabrication of three type nanodevices. For Type I devices, the Ti electrodes make an Ohmic contact directly on the nanowire and these devices expose intrinsic nanowire behaviors. Electron transport of Type I devices exhibited thermally activated transport and three-dimensional Mott variable range hopping at high and low temperatures, respectively. For Type II devices, two-Schottky contacts of TiOx/Au electrodes are deposited on nanowires in formation of an electrical depletion field, compressing nanowire channel to form a quasi-one-dimensional conducting path. For Type III devices, two-Ohmic contacts are made at the end of individual ZnO nanowires, taken as source and drain electrodes. Pt electrode was then patterned in the middle of the nanowire, acting as a floating electrode. Due to the high work function of Pt, we expect to develop a Schottky contact which depletes the nanowire conducting channel. We have observed that, in both Type II and III devices, the resistance and the current-voltage characteristics follow the power law with α~ 2 - 6 and with β~ 3 - 7. Both R(T) and I(V) reveal the features of the Luttinger liquid system. Moreover, all I-V curves at different temperatures for Type II and III devices can collapse onto a single universal curve in the plot of I/T1+α versus eV/kBT, coinciding with the prediction of transport in the one-dimensional Luttinger liquid system.