利用連續流動型反應進行蜂巢狀圖案化氧化鋅側向磊晶成長之研究

Aqueous lateral exitaxial overgrowth of ZnO layers on honeycomb patterned buffer layers through a Continuous Flow Reactor

楊舒涵

氧化鋅 ； 圖案化製程 ； 水熱法 ； 側向磊晶成長 ； 晶體缺陷 ； ZnO ； lateral epitaxial overgrowth ； hydrothermal growth ； crystal defects ； patterning process

義守大學材料科學與工程學系學位論文

2017年

碩士

陳厚光

繁體中文

由於成長高品質氧化鋅磊晶膜層一直是致力想達成的目標。欲進一步降低磊晶膜層中差排密度，可以在製程中搭配圖案化製程進行側向磊晶成長(Lateral epitaxial overgrowth, LEO)。在前期研究透過 “線陣列”圖案化緩衝層陣列輔助，並搭配低溫水熱法製程在藍寶石基板上進行氧化鋅無遮罩式側向磊晶成長，並獲得低差排密度癒合氧化鋅膜層。然而磊晶膜層中仍存在著Wing tilt效應(約0.1o)；為了改善wing tilt效應，在前期研究中提出六角形點陣列緩衝層，搭配“連續流動型反應器”，以進行長時間側向磊晶成長，可以獲得wing-tilt-free的磊晶膜層。 在本實驗中，將嘗試在藍寶石基板上製作另一種六重對稱圖案ZnAl2O4緩衝層結構─六角蜂巢圖案，再透過水熱法成長來進行ZnO側向磊晶成長。其中將嘗試採用兩種不同蜂巢圖案開口及圖案間距圖案尺寸來製作圖案ZnAl2O4緩衝層結構；此外，也分別嘗試利用傳統封閉式水熱法及連續流動型反應器來進行氧化鋅側向磊晶成長。其中透過傳統封閉式水熱法需要經常中斷晶體成長並更換水溶液來進行側向磊晶成長，由於經常中斷緣故，導致在側向成長最後階段，在蜂巢結構中心之未癒合孔洞上會發生氣泡會附著，進而導致蜂巢結構孔洞無法癒合，而且從橫截面觀察，可以發現在孔洞內為一個未癒合中空的孔穴。而透過連續流動反應槽來進行長時間氧化鋅側向磊晶成長，經過96小時以上成長，可以獲得完全連續癒合的膜層。證實可以透過採用連續流動反應槽來改善傳統水熱法更換溶液的問題。從XRC分析結果在蜂巢狀陣列上進行LEO成長之氧化鋅膜層幾乎完全沒有Wing tilt效應。薄膜整體平均差排密度為108 pitting/cm2。在癒合LEO膜層不同部位之顯微結構，分別透過穿透式電子顯微鏡及微區光激發螢光譜量測來進行探討。

In this study, the growth of high quality zinc oxide (ZnO) epitaxial layer is the major objective. To further reduce dislocation density, lateral epitaxial overgrowth (LEO) integrating with patterning processing had been proposed. In previous study, maskless LEO of ZnO on sapphire substrate in low temperature aqueous solution, through the assistance of line-patterned buffer layer, was reported. Although the dislocation density had been reduced, the effect of wing-tilt(a tilt angle of 0.1o) remained in the LEO ZnO layer. To suppress the wing-tilt effect, in our previous work, lateral epitaxial overgrowth of ZnO layer on hexagonal-patterned ZnAl2O4 buffer layers, with continuous flow reactors to conduct long duration epitaxial growth (>24h), can almost prevent the impact of wing-tilt effect. In this work, another pattern design with hexagonal symmetry, honeycomb pattern, was used to fabricated patterned ZnAl2O4 buffer layers on sapphire substrates. In this study, two different size of honeycomb patterned buffer layer was adopted to perform LEO. Aqueous lateral exitaxial overgrowth of ZnO layer was implemented on honeycomb patterned buffer layer through a conventional autoclave vessel or a continuous flow reactor, respectively. For conventional autoclave vessel, the crystal growth always needs to be interrupted to refresh the growth solution; meanwhile, the formation of the bubble on the center of honeycomb pattern obstruct the growth of ZnO in lateral directions; as a result, the fully coalesced ZnO layer cannot be achieved by the hydrothermal processing with conventional autoclave vessel. In contrast, for aqueous lateral exitaxial overgrowth of ZnO layer through the continuous flow reactor to implement long-duration hydrothermal growth, after LEO growth for 96h, the film was fully coalesced. It is evident that the LEO of ZnO through a continuous flow reactor can prevent the impact of gas bubbles. Based on X-ray diffraction rocking curve measurement, the wing-tilt was almost absent. The average dislocation density in the coalesced LEO layer was about 108 pitting/cm2. The microstructures and optical properties of coalesced ZnO film was implemented by transmission electron microscope and micro photoluminescence measurement.

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