氧化鋅/碲化鋅 核殼奈米線陣列於透明氧化導電玻璃基板上成長與特性分析

Abstract

核殼奈米線陣列的堆疊異質接面近年來吸引了許多注意，因為它與一般的平面元件相比有較高的表面積跟體積比和較好的光捕捉性質。更重要的是因為它的能帶結構可使電子和電洞分離到不同的區域，藉此可以增加載子生命期。 此論文主要研究氧化鋅/碲化鋅的核殼奈米線成長和晶體結構、光學、電學等性質。藉由化學氣相沉積和有機金屬化學氣相沉積，氧化鋅/碲化鋅核殼奈米線陣列垂直成長於透明導電玻璃基板上。接著使用掃描式電子顯微鏡、穿透式電子顯微鏡和X光繞射儀了解晶體結構，再藉由光致螢光量測和穿透光譜了解光學性質。 利用氧化鋅/碲化鋅核殼奈米線陣列，製作一個光伏元件來研究它的光電特性。測量電流密度跟電壓的曲線圖和隨時變電流密度變化，結果顯示照光下的光電流會變大且反應時間也變快，由此可證明載子可在堆疊異質接面中分離。

Type Ⅱ heterojunction core-shell nanowire arrays have attracted much attention recently because they have advantages over conventional planar devices, such as higher surface-to-volume ratio and better light-trapping effect. Moreover, because of the type-II band alignment, electrons and holes are naturally separated into different spatial regions in these nanowire structures and thus the carrier lifetime is increased in these structures as compared with the normal devices. In this thesis, we report the growth and characterization of ZnO/ ZnTe core-shell nanostructure. Vertically aligned ZnO/ZnTe core/shell nanowire arrays on transparent conducting oxide glass substrates were fabricated by using chemical vapor deposition (CVD) to grow the ZnO core and metal organic chemical vapor deposition (MOCVD) was used to deposit the ZnTe shell. The morphology of ZnO/ZnTe core/shell nanowire arrays were studied by scanning electron microscope (SEM); the detailed atomic arrangement of the ZnO/ZnTe core/shell nanowire was investigated by transmission electron microscopy (TEM). The crystal structures of ZnO/ZnTe core/shell nanowires were characterized by X-ray diffraction (XRD). The optical properties of ZnO/ZnTe core/shell nanowire arrays were investigated by photoluminescence (PL) and transmission studies. The ZnO/ZnTe core/shell nanowires arrays were then used as the active layer and carrier transport medium to fabricate a photovoltaic device. The current density versus potential curve and time-dependent photocurrent density were measured for this device. The results showed the ZnO/ZnTe core/shell nanowire array has enhanced photocurrent and good photocurrent response under light illumination, indicating the nanowire arrays can be made into a good photovoltaic device.