探討硫化鉛奈米線是否為拓樸絕緣體

Abstract

我們利用兩點測量法觀察其電性傳輸性質，並量測在300 K - 80 K不同溫度下的電阻值與電流-電壓曲線，硫化鉛奈米線為半導體性質。其中我們利用二維變程跳躍模型來解釋PbS的傳輸性質，發現電子在表面進行傳輸。我們計算其侷域長度等相關性質對W/L (寬度/長度)作比較。接著我們利用背閘極偏壓觀察其在不同溫度下的場效應變化，發現在溫度越低下，其雙極性的行為越明顯。而完整的雙極性現象發生在約240 K-210 K之間。接著計算其ON/OFF Ratio對W/L作關係圖比較。透過照光實驗，觀察光反應的強度、光電流與溫度及照射光強度的關係變化。而在溫度225 K左右時光電流可以觀察到有轉折的變化，推測此溫度可能與硫化鉛的Debye temperature有關也與出現完整雙極性的現象有關係。

Topological insulators have attracted scientists’ attentions for years. It was proposed theoretically that the lead chalcogenides PbX (with X=S. Se, or Te) have a great potential to be topological insulators. In this work, we fabricate field effect transistors of lead sulfide nanowires by electron-beam lithography and thermal evaporation and we study electrical properties. We measured electron transport and field effect characteristics of lead sulfide nanowires at the temperature range from 300 to 80 K. The electron transport measurement shows the semiconducting behavior of lead sulfide nanowires. The model of two dimensional variable-range-hopping describes well the transport data of lead sulfide nanowires. It indicates that the electrons transport is confined on the surface. In addition, the device shows ambipolar gating behaviors at low temperature. Especially, the apparent ambipolar behavior appears at 225K. In the photoresponse measurement, we detected a transition in photoconductance at 225 K , and it could be associated with Debye temperature of PbS nanowires.