利用氣液固相法成長硫族合金鍺碲單晶奈米線

Abstract

本研究利用氣液固相法（Vapor-Liquid-Solid，VLS），以金（Au）奈米粒子為催化劑及95%氬氣（Ar）與5%氫氣（H2）混合氣體為載流氣體，成長鍺碲（GeTe）硫族合金（Chalcogenide）單晶奈米線（Nanowire，NW）。以濺鍍法將約4 nm厚之Au薄膜鍍於矽（Si）基板上，再施予600C、1分鐘之退火處理，利用降低總表面能的原理形成Au奈米粒子。之後將覆有Au奈米粒子的Si基板置於已載有鍺碲（GeTe）粉體源的三溫區高溫爐中，調變基板溫度、爐管壓力及載流氣體流量以長成GeTe NW。描式電子顯微鏡、能量散佈分析儀及X光繞射儀之分析顯示，GeTe NW可於爐管壓力為1 torr，載流氣體流量/基板溫度為0 sccm/425C、50 sccm/425至450C、100 sccm/425至475C、1000 sccm/400至450C之條件下長成，NW的直徑約在 200至300 nm，長度可達30 m，且實驗結果顯示GeTe NW數量隨著載流氣體流量增大而增加。穿透式電子顯微鏡分析顯示NW沿著菱方晶 軸向成長，且其Ge與Te之化學劑量比約以1：1之比例均勻分布於NW中。

This study investigates the synthesis of single-crystalline germanium telluride (GeTe) chalcogenide nanowire (NW) by vapor-liquid-solid (VLS) method. First, the 4-nm thick gold (Au) film was deposited on (Si) substrate via sputtering method and the annealing at 600C for 1 min was carried out to form the Au nanoparticles which serve as the catalyst for subsequent NW growth. Afterward, the Si substrate clad with Au nanoparticles was transferred to a three-zone furnace containing GeTe powder source in order to facilitate the growth of NWs at various temperatures, pressures and carrier gas flow rates. With the analytical results of scanning electron microscopy, energy dispersive spectroscopy and x-ray diffraction, it was found that, at the pressure of 1 torr, the GeTe NWs with the diameter in range of 200-300 nm and the length up to 30 m can be achieved at the flow rate/temperature conditions of: 0 sccm/425C, 50 sccm/425-450C, 100 sccm/425-475C and 1000 sccm/400-450C. Moreover, an increasing number of NW was observed when the carrier gas flow rate was increased. Transmission electron microscopy characterization indicated the GeTe NWs grow along the -axis direction of the rhombohedral lattice and the Ge and Te elements uniformly distribute along NWs with the stoichiometric ratio of 1:1.