鋅-氧化鋅奈米晶體之熱還原成長製程與物理特性研究

Abstract

本研究利用熱蒸發與沉積的製程，成功地在矽基板上生長出六方結構的鋅-氧化鋅特殊多面體奈米結構。一般而言，結晶相與成核的種子的控制，對於奈米晶體在成長開始時的本質形狀是很重要的，因此在實驗中，將含有金屬鋅離子的有機溶液先塗佈在基板上，並以此作為成核的種子。再利用熱蒸氣傳輸製程以氧化鋅粉末為成長源，並通入純氬氣，而在基板溫度為250℃下即可成長。結果發現，未作任何後段處理的鋅-氧化鋅多面體奈米結構其實是由六方結構的金屬鋅與外層氧化後的氧化鋅薄膜所組成。並且隨著根據不同的成長溫度與反應氣氛，發現鋅-氧化鋅多面體奈米結構會有形貌上的變化。同時進一步施予不同的熱處理來觀察此鋅-氧化鋅多面體奈米結構的形貌與結晶性。可以確定其成長機制應該是由金屬鋅與氧化鋅間無機的架橋機制而來。另外，這些特殊多面體奈米結構在光激發光光譜中顯示出微弱的紫外光發光特性，但是可以藉由後段的氣氛處理來改善其光激發光特性與結晶性。

Novel hierarchical polygon prismatic nano-structures of wurtzite Zn-ZnO have been successfully grown on silicon by thermal vapor transport and condensation method. Generally, the crystalline phase and control of the seeds at the nucleating stage are critical for directing the intrinsic shapes of nanocrystals at the initial time. Thus, in this work, the organic solvent with zinc chemical compound was first coated and used as seeds on the patterned substrate. Subsequently, it was grown by thermal vapor transport with ZnO powder at 250°C (substrate) in Ar atmosphere. The samples were characterized using X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence spectroscopy. The as-synthesized Zn-ZnO polygon prismatic nano-structure consisted of hexagonal metallic nuclei (Zn) covered with an oxidation outer thin film (ZnO). Depending on different working temperature and reaction atmosphere, Zn- ZnO polygon prismatic structure having various morphologies can be developed. In order to recognize the growth mechanism of Zn-ZnO polygon prismatic structure and temperature effect, different heat-treatment were designed to observe the morphology and crystallization of Zn-ZnO polygon prismatic structure. The possible formation mechanism for the Zn-ZnO polygon prismatic crystal structure is identified and proposed as the Zn-ZnO mineral bridge mechanism. The non-perfect Zn-ZnO polygon prismatic structure shows weakly UV emission and strongly deep-level emission. However, the PL properties and crystallization of Zn-ZnO polygon prismatic nanocrystals could be improved by suitable post-treatment.