氧化鋅/碲化鋅核殼奈米線及摻雜銻元素P型氧化鋅陣列光學與電學性質之研究

Abstract

氧化鋅奈米結構具有極優的光電性質與化學特性，使得近年來在氧化鋅奈米結構在透明電極、致動、感測、和光電應用上，吸引許多科學家的研究。而我也在氧化鋅奈米線的成長與光電性質上也有所研究。在此論文中，我們研究分為兩個部分，一是氧化鋅/碲化鋅核殼奈米線成長及光電性質分析、一是摻雜銻元素P型氧化鋅陣列的光學性質分析。 在氧化鋅/碲化鋅核殼奈米線部分，我們利用化學氣相沉積法及有機金屬汽相沉積法成長氧化鋅/碲化鋅核殼奈米線陣列，因氧化鋅奈米線陣列具有高的光吸收率及抗反射率，加上氧化鋅/碲化鋅異質結構為一個良好的P-N接面，因此，此結構可廣泛應用於太陽能電池，光偵測器及任何相關的光伏元件。 在另一方面，我們也利用電鍍法成長出摻銻元素P型氧化鋅陣列。我們也利用許多儀器去分析，發現用此方式可以成長出良好的晶體，而樣品也同時展現出良好的光學與電學性質，並在室溫光激螢光實驗下呈現紫色螢光，此現象可廣泛應用於短波長發光元件上。而相較於其他製程設備的昂貴價格，製程簡單的電鍍法也許在未來發展成為一個低成本、商業化製程的方法。

Zinc Oxide (ZnO) nanostructures have recently attracted much attention in various research topics. Its direct wide band gap of 3.37eV and relatively large exciton binding energy are promising on the applications such as ultraviolet detection and emission, respectively. In addition, a high surface-to-volume ratio of ZnO structures has an excellent light trapping efficiency, so it can be utilized on the photovoltaic devices. In this study, we report the growth and characterizations of ZnO/ZnTe core/shell nanowires array on the indium tin oxide. Properties of the ZnTe layer coated on well-aligned vertical ZnO nanowires has been demonstrated by scanning electron microscope, tunneling electron microscope, X-ray diffraction pattern, photoluminescence, and transmission studies. The ZnO/ZnTe core/shell nanowires array was then used as the active layer and carrier transport medium to fabricate a photovoltaic device. The enhanced photocurrent and faster response observed in ZnO/ZnTe, together with the quenching of the UV emission in the PL spectra, indicate that carrier separation in this structure plays an important role in determining their optical response. The results also indicate that core/shell structure can be integrated into useful photovoltaic devices. On the other hand, Sb-doped ZnO microrods array was fabricated on Al-doped ZnO thin film by electrodeposition. A strong violet luminescence, dominated by the free electron to acceptor level transitions, was revealed by temperature-dependent photoluminescence measurements. This acceptor-related transition was attributed to the formation of the SbZn-2VZn complex due to substitution of Sb dopants for Zn sites, instead of O sites, to form a complex with two Zn vacancies (VZn). This SbZn-2VZn complex has a lower formation energy and acts as a shallow acceptor which can induce a strong violet luminescence. The photo-responsivity of ZnO homojunction device at a negative bias demonstrated a nearly 40-fold current gain, illustrating that our device is potentially an excellent candidate for photodetector applications in the ultraviolet wavelength region.