化學氣相沉積氧化鋅磊晶薄膜於YSZ基板之研究

Abstract

本論文主要研究方向在使用化學氣相沉積法製作氧化鋅磊晶薄膜，包含金屬有機化學氣相沉積(metalorganic chemical vapor deposition, MOCVD)及原子層化學氣相沉積(atomic layer deposition, ALD)兩部分，並以高溫退火處理，嘗試增進其發光特性。在MOCVD部分以Si及YSZ做為基板在不同溫度成長氧化鋅，並嘗試以兩階段成長改善表面粗糙度。ALD部分以Si、YSZ、康寧玻璃為基板，在300 oC成長氧化鋅，測試ALD在磊晶方面之效果。分析部分以SEM、AFM觀察其表面形貌，XRD、TEM分析其結構，PL量測發光特性，SIMS分析鍍膜過程是否有雜質進入薄膜。 MOCVD實驗結果方面，以Si為基板成長溫度由低溫至高溫，氧化鋅由二維方向成長轉變為三維方向成長，發光特性亦由UV emission為主轉變為green emission漸強的趨勢。YSZ基板則皆為氧化鋅磊晶薄膜，磊晶關係(0002)ZnO∥(111)YSZ，在低溫有較佳結晶品質，但出現二次成核成長晶粒，採用兩階段成長則可成功避免二次成核，獲得高度均勻平坦氧化鋅磊晶薄膜，發光特性與Si基板部分相似在高溫成長時green emission訊號逐漸變強，使用氧氣氛爐管高溫退火則使UV emission減弱、green emission增強，快速升溫退火則有相反趨勢UV emission增強、green emission減弱。SIMS分析結果則顯示氧化鋅內部沒有前驅物分子團殘留，是純度極高的氧化鋅薄膜。 ALD部分僅YSZ基板部分可獲得磊晶薄膜，磊晶關係(0002)ZnO∥(111)YSZ，發光特性部分UV emission與green emission訊號強度幾乎一樣，快速升溫退火對其發光性質略有改善，但效果不大。

In this study, epitaxial ZnO thin films were deposited by mtealorganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD). High temperature annealing was used to enhance optical property. ZnO films on Si and YSZ were deposited by MOCVD at various temperatures. Two-step growth was used to improve the surface roughness. Besides, ZnO films on Si, YSZ and glass were deposited by ALD at 300 oC. The structural properties of ZnO thin films were characterized by XRD and TEM, the surface morphology was characterized by SEM and AFM, the optical property was characterized by PL, the impurities were characterized by SIMS. For the ZnO deposited on Si by MOCVD, as the growth temperature increased, ZnO has been found to be from 2D growth change to 3D growth, and the intensity of green emission were increased. For the ZnO deposited on YSZ by MOCVD, all samples showed the epitaxial relationships between the film and substrate were (0001)ZnO||(111)YSZ. ZnO grown at lower temperatures had better crystal quality, however, second nucleation grains appeared on the surface. Flat ZnO tnin films were deposited by MOCVD in two-step growth. The optical property were similar to the ZnO on Si substrate. After annealing treatment in oxygen ambient, intensity of UV emission decreased while the intensity of green emission increased. However, after RTA treatment in nitrogen ambient, intensity of green emission decreased while the intensity of UV emission increased. The result of SIMS analysis showed that the purity of ZnO was high because of no precursor remained in the film. For the ZnO deposited by ALD,epitaxial ZnO might grow on YSZ and the epitaxial relationship between the film and substrate was (0001)ZnO||(111)YSZ. The intensities of UV emission and green emission were almost equal. The optical properity only had a little improvement by RTA treatment, but its effect was not good.