- 學位論文
利用氮氣快速熱退火處理促進P型氮化鎵基板上氧化鋅奈米柱之成長
Using Nitrogen Rapid Thermal Annealing to Enhance The Growth of Zinc Oxide Nanorods on p-GaN Substrate
摘要
為克服p-GaN與ZnO約1.8%的晶格不匹配，多數文獻中會以一層薄薄的ZnO當作晶種層，但ZnO 晶種層如果品質不佳，將會影響整體的發光效率，導致發光效率降低，而本實驗利用快速熱退火克服了未使用晶種層便能夠成功成長高均向性一維氧化鋅奈米柱陣列。 本實驗利用快速熱退火克服p-GaN難以成長奈米柱之狀況後以水熱法(Hydrothermal)於p-GaN基板上合成出高均向性一維氧化鋅奈米柱陣列。以醋酸鋅(Zn(CH3COO)2‧H2O)與四氮六甲圜(C6H12N4)之混合溶液，固定其反應時間與溫度，以不同退火溫度及溶液濃度為改變參數合成氧化鋅奈米柱，探討p-GaN退火後之影響與奈米柱陣列的發光特性。 以掃描式電子顯微鏡(SEM)鑑定氧化鋅晶體結構與表面型態，光激螢光光譜(PL)顯示氧化鋅奈米柱具有紫外光和寬頻之可見光發光區域。經過實驗結果分析，可得知改變退火溫度對氧化鋅奈米柱成長的影響以及不同濃度之PL發光強度，而室溫下之PL量測主要由free exciton主導。
並列摘要
In order to overcome the lattice mismatch of about 1.8% between ZnO nanorods and GaN substrate, the use of a thin ZnO seed layer has been reported by the majority of the literature. The quality of ZnO seed layer certainly then affected the overall luminous efficiency of the ZnO nanorods prepared. In this study, we used a hydrothermal method to deposit ZnO nanorods on p-GaN subtrate without the ZnO seed layer but with an annealing treatment of the GaN substrate. Although it is difficult to directly deposit ZnO nanorods on GaN substrate, we found that the use of rapid thermal annealing (RTA) pretreatment of the GaN substrate could help to successfully deposit ZnO nanorods on p-GaN substrate. A mixed solution of different compositions of zinc acetate (Zn(CH3COO)2‧H2O) and hexamethylenetetramine (C6H12N4) was used to deposit ZnO nanorods. To find the optimal temperature for RTA, we varied the RTA temperature but fixed the deposition time and temperature and then compared the corresponding results obtained. A scanning electron microscope (SEM) was used to identify the crystal structure of zinc oxide and surface morphologies. Moreover, the photoluminescence (PL) spectroscopy showed both a sharp ultraviolet band dominated by the free exciton and a broad visible band originated from defects. The experimental results demonstrated that the RTA pretreatment of p-GaN subtrate is critical to achieve good quality ZnO nanorods on top. An RTA temperature of 500℃ could present a strong UV band with the visible band being suppressed.