單一摻鈷氧化鋅奈米柱低溫強磁之電子傳輸行為研究

Abstract

本篇論文研究摻鈷氧化鋅奈米柱在低溫強磁的環境中電阻隨磁場變化的機制，磁場範圍為-5 Tesla到7 Tesla，並利用電子束微影、介電湧動法及聚焦離子顯微鏡製作單根氧化鋅的量測元件，在各個不同的溫度下所得到的I-V曲線皆為接近線性及對稱，摻鈷氧化鋅奈米柱不論是在5K或室溫都可觀察到磁滯曲線，也可看到其殘磁隨著鈷摻雜量提高而上升，鈷摻雜的氧化鋅在提供外加磁場的情況下電阻會有些微的上升，約佔整體電阻的1%，因為鈷摻雜會造成傳導帶的能接分裂而磁場造成電子的重新分佈，造成電阻的上升。而無摻雜鈷的氧化鋅在磁場下電阻則是會有明顯的下降，其原因則歸於外加磁場破壞了弱局域效應造成電阻的下降。

This study examined carrier transport in single cobalt-doped ZnO nanorod under magnetic field of -5 Tesla to 7 Tesla at low temperature. Measurements were taken on single nanorods deposited on a Si template, where two point metallic contacts were previously made using e-beam lithography, dielectrophoresis, and focused ion beam. In two probe measurements, the current-voltage curves were clearly linear and symmetrical with respect to both axes in temperatures ranging from 1.4 K to 300 K. The Co-doped nanorods exhibited ferromagnetic behavior from room temperature to 5 K and the remanence permanent magnet of the nanorods increased with increasing Co concentrations. When applied magnetic field, the electrical resistance of Co-doped ZnO increases about 1%. We attribute the increase of resistance in the Co-doped ZnO nanorod to the splitting of conduction band and the re-distribution of electrons under magnetic field. On the contrary, the magnetoresistance of pure ZnO nanorods was decreased because of the breakdown of the weak localization under magnetic field.