利用超音波輔助霧化化學氣相沉積法進行功能性氧化物磊晶薄膜成長之研究

The Study on the Epitaxial Growth of Functional Oxide Films by Ultrasonic Assisted Mist Chemical Vapor Deposition

葉同倫(Tung-Lun Yeh)

指導教授 ： 陳厚光

義守大學/理工學院/材料科學與工程學系/碩士(2021年)

摘要

為了發展全氧化物電子元件，其中p-n接面是電子技術中許多元件的基礎，由於本實驗室已經成功生長n型ZnO磊晶薄膜，為了挑選與ZnO結構上匹配的材料，因此選用尖晶石結構之p型氧化物半導體Co3O4與ZnCo2O4。
霧化化學氣相沉積法(Mist-CVD)為設備簡單、常壓製程、低成本、低環境負擔需求之製程，有別於有機金屬化學氣相沉積(MOCVD)所採用的易燃、易揮發、昂貴、高毒性的有機金屬前驅物。因此本研究採用Mist-CVD製程，且目前尚未有人發表利用Mist-CVD生長鈷系氧化物磊晶薄膜相關研究。
本論文分成兩部分，第一部分為生長CoO及Co3O4薄膜。探討腔體溫度、攜帶氣體、載台及基板對磊晶薄膜成長的影響。結果顯示，腔體溫度在450°C、氮氣作為攜帶氣體，將有利於單相CoO成長，此外同時將試片水平放置在玻璃基板上，將可以成長均勻且平坦CoO磊晶薄膜；腔體溫度為500°C，並採用氧氣作為攜帶氣體，將有利於單相Co3O4磊晶薄膜成長，此外需要同時採用試片傾斜45˚擺放之三角石英載台，為Co3O4薄膜較佳生長條件。XRD φ-scan分析實驗結果顯示CoO及Co3O4可以分別在a-及c-plane藍寶石與雲母基板上呈現六重對稱繞射特徵，顯示可以成功透過常壓超音波霧化化學氣相沉積製程在各種基板上進行CoO及Co3O4磊晶薄膜成長。接著透過退火比較前後電學性質差異，結果顯示，CoO在氧氣氛中650 oC退火，將會轉變成Co3O4相。退火過後試片其電阻率: 1.42×101 Ω-cm、載子濃度:4.37×1016 cm-3並呈現p型半導體電性。
第二部分為生長ZnCo2O4磊晶薄膜。同樣嘗試在不同基板上生長，透過XRD φ-scan分析，在a-plane藍寶石基板上ZnCo2O4出現晶體旋轉30o晶域結構，而在c-plane藍寶石基板、雲母基板則是呈現單一磊晶方位取向。為了改善在a-plane藍寶石基板上成長ZnCo2O4磊晶膜層中30°旋轉晶域，將嘗試利用與ZnCo2O4結構相同之Co3O4及ZnAl2O4作為緩衝層來進行單一磊晶方位取向ZnCo2O4薄膜成長。結果顯示採用Co3O4及ZnAl2O4緩衝層皆為可以成功在a-plane藍寶石基板上成長單一晶域之ZnCo2O4薄膜。接著再探討退火處理對ZnCo2O4薄膜電學性質影響，結果顯示，退火後電阻率為6.01×101 Ω-cm、載子濃度為6.43×1015 cm-3，為p型ZnCo2O4薄膜最佳電學性質。

關鍵字

氧化鈷 ； 氧化鋅鈷 ； 霧化化學氣相沉積 ； 磊晶

並列摘要

To develop all-oxide electronic devices, the p-n junction is the basis of many components in electronic technology. In our laboratory, epitaxial growth of n-type ZnO films has been successfully performed, in order to match the lattice structure of ZnO for epitaxial growth, the Co3O4 and ZnCo2O4 that had spinel stracture were selected as p-type oxide semiconductor.
Mist chemical vapor deposition (Mist-CVD) is a simple system configuration, non-vacuum, low-cast, and low environmental load process, in contrast to metal-organic chemical vapor deposition (MOCVD) which used a flammable, volatile, expensive, and highly toxic metal-organic precursors. Therefore, Mist-CVD process was adpoted to implement the epitaxial growth of cobalt oxide films in this work. Remarkably, the limited study of cobalt oxide epitaxial fims grown by Mist-CVD have been reported.
This thesis divides into two parts. The first part is the growth of CoO and Co3O4 films. The influence of temperature, carrier gas, holder, and substrate on the epitaxial growth of cabalt oxide thin films was investigated. The results show that the single phase CoO thin films were favorably grown at the growth temperature of 450 oC and the use of nitrogen as carrier gas; in addition, uniform and flat CoO epitaxial films can be obtained by horizontally placing substrates on a glass slides. The use of oxygen as carrier gas at the temperature of 500 oC was more favorable for epitaxial growth of single phase Co3O4 films grown; besides, the growth of Co3O4 films with uniform morphology were achieved by using a 45o-inclined quartz holder. The XRD -scans of the CoO and Co3O4 films grown on a-, c-plane sapphire, and mica substrates, respectively, revealed six-fold symmetry, indicating that the epitaxial growth of CoO and Co3O4 films were successfully performed on various substrates by an atmospheric pressure Mist-CVD process. Moreovre, the effect of annealing treatment on the electrical properties of cobalt oxide films were studied. The results show that the CoO phase converted into Co3O4 phase after annealing at 650 oC in oxygen ambient, and the annealed sample exhibited p-type semiconducting properties with electrical resistivity of 1.42×101 Ω-cm and the carrier concentration of 4.37×1016 cm-3.
The second part of the thesis is the growth of ZnCo2O4 films on different substrates. The XRD φ-scan analysis shows that the 30o-rotated domains was present in the ZnCo2O4 film grown on a-plane sapphire substrate; in contrast, ZnCo2O4 films with single domain were epitaxially grown on the c-plane sapphire and mica substrate. In order to eliminate the 30°-rotated domain in ZnCo2O4 layer grown on a-plane sapphire, Co3O4 and ZnAl2O4, which have same lattice structure as ZnCo2O4, were used as the buffer layer for the epitaxial growth of ZnCo2O4. The results show single domain ZnCo2O4 epitaxial films can be grown on a-plane sapphire substrates by using Co3O4 and ZnAl2O4 buffer layers, respectively. Moreover, the effect of annealing treatment on the electrical properties of ZnCo2O4 films were investigated. The results show that the annealed sample exhibited p-type semiconducting properties with electrical resistivity of 6.01×101 Ω-cm and the carrier concentration of 6.43×1015 cm-3.

並列關鍵字

CoO ； Co3O4 ； ZnCo2O4 ； Mist-CVD ； Epitaxial growth

參考文獻

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