水熱法合成摻鋰氧化鋅奈米線之電子傳輸與壓電特性研究

Abstract

本實驗以醋酸鋅及六亞甲基四胺、醋酸鋰為先驅物，使用水熱法成長鋰參雜氧化鋅奈米線，並以多步驟水熱法成長，可有效增加奈米線長度及長寬比。利用X光繞射儀及穿透式電子顯微鏡進行結構鑑定，發現奈米線為單晶六方晶系結構，且以電子能量散失能譜儀確認裡摻雜於氧化鋅奈米線中。以變溫PL及分光光譜儀分析奈米線之光學性質，發現摻鋰將使氧化鋅奈米線產生次能隙，使能隙下降60 meV，並產生一淺層受體能階 93.6 meV。利用超導量子干涉儀發現此奈米線具有稀磁性，常溫下矯頑磁場約為166厄斯特(Oe)，飽和磁化率約為9.64 memu/g。可用於稀磁記憶體或電子自旋元件等諸多應用。 將合成摻鋰氧化鋅奈米線製成單根奈米線場效電晶體量測，得到奈米線電阻率約為0.025Ωcm，且當閘極通負偏壓時，汲極電流上升，明顯為p型半導體傳輸特性，經計算得到電洞遷移率為14.59 cm2/V．s，電洞濃度約為1.15 ×1017/cm3 。其次，以AFM進行壓電特性量測，發現單根摻鋰氧化鋅奈米線之輸出電流較純氧化鋅奈米線有明顯提升，可大幅提升氧化鋅奈米線的壓電效應。

Well-aligned Li-doped ZnO nanowires(NWs) were synthesized on Si substrates with GZO seed-layer by hydrothermal method , using Zn(CH3COO)2 ,HMTA, and Li(CH3COO) mixed solution as the precursor. By multiple-step growth, the length and aspect ratio of nanowires were increased with step of growth. HRTEM image and XRD spectrum clearly shows the wurzite ZnO is single-crystalline, and grown along the [0001] direction. EELS spectrum of Li K-edge peaks demonstrated the existence of lithium in the ZnO NWs. The acceptor energy level of the Li dopant was estimated to be 93.6 meV from the temperature-dependent photoluminescence spectra. UV-Vis spectrum also shows Li-doped ZnO nanowires produce sub-bandgap. By SQUID measurements, the coercivity and saturation magnetization of the Li-doped NWs at room-temperature were 166 Oe and 9.64 memu/g, respectively. Additionally, the electron transport property of Li-doped ZnO NWFET confirms that the NWs is p-type, which exhibited high carrier mobility of 14.59 cm2/V．s and an effective hole carrier concentration of 1.13×1017 cm-3. The piezoelectric response of the NWs was measured by AFM with a Pt-coated Si tip, which shows that the Li-doped ZnO NWs produce much higher piezoelectric output current than pure ZnO NWs