- 學位論文
以射頻濺鍍系統沉積製備摻鋁氧化鋅薄膜特性分析
Properties of AZO films fabricated by radio frequency sputtering
摘要
在本論文中，我們描述利用利用射頻濺鍍系統製備氧化鋅鋁(AZO)薄膜，並使用純度99.99%摻雜2wt%氧化鋁的混合氧化鋅鋁靶材，進行結構、表面形態、光電特性之分析。首先，於玻璃基板上成長氧化鋅鋁薄膜，並藉由改變濺鍍功率(150W-500W) 來探討其薄膜特性。由x-ray 繞射與掃描式電子顯微鏡量測，發現薄膜的從優取向皆為(002)面及(004)面。隨著瓦數提高，沉積速率越快，氧化鋅鋁薄膜的厚度也增加。在霍爾電性量測下，氧化鋅鋁薄膜在濺鍍功率為500W 有較好的品質。 接下來，我們在固定的濺鍍功率下(500W)成長於玻璃基板上，沉積溫度從室溫至250℃，來探討其薄膜特性。在x-ray 繞射量測中，皆呈現的c軸的從優取向。原子力顯微鏡及掃描式電子顯微鏡結果可得150℃沉積的圓柱型態氧化鋅鋁薄膜有最均勻平坦的表面結構，且在霍爾電性量測下得到最低電阻率3.60×10-4 Ω cm、最高遷移率28 cm2/V s及最高電子濃度為6.22×1020 cm-3。此外，由室溫光激螢光量測顯示，當沉積溫度從室溫增加到150℃，主要的發光波段有藍位移現象(3.15 to 3.18 eV)，其發光來源為中性施體束縛的束縛態激子。而沉積溫度250度之氧化鋅鋁薄膜，其主要發光峰值略為下降至3.17eV並發現有受體缺陷鋅空缺(V Zn )所致的發光。由室溫光激螢光量測峰值的結果可發現與光吸收能隙的改變相互印證。穿透特性方面，氧化鋅鋁薄膜穿透率皆達80%至85%。
並列摘要
This thesis, focuses on the characterizations of Aluminum-doped ZnO (AZO) semiconductors fabricated by radio frequency sputtering system. A sintered ceramic target with a mixture of ZnO (purity: 99.99%) and Al2O3 (purity: 99.99%) was used. The percentage of Al2O3 in the AZO target was 2 wt%. The structural, surface morphology and electrical properties of AZO films were examined. First, AZO films on glass substrate prepared at various RF powers ranging from 150 to 500W were examined and compared. X-ray diffraction analyses and scanning electron microscopy images indicated that the preferred grain orientation of all AZO films was (002) and (004). The deposition rate and thickness of AZO films increases with increase in RF power. Hall measurement at room temperature demonstrated a good-quality film could be obtained with RF power of 500W. Next, we examined properties of AZO films deposited on glass substrates at various substrate temperatures ranging from room temperature to 250℃. X-ray diffraction patterns demonstrated that all the films were grown with a preferential orientation of c-axis. Atomic force microscopy and scanning electron microscopy images showed a uniform grain structure with smooth surface for the film deposited at 150℃. This film also revealed the highest Hall mobility of 28 cm2/Vs, the lowest resistivity of 3.60×10-4 Ω cm with the electron concentration of about 6.22×1020 cm-3. Moreover, the RT-PL spectrum demonstrated the blue shift of dominated emission line from 3.15 to 3.18 eV as the deposition temperature increased from RT to 150℃. The dominated emission is ascribed to the recombination of neutral donor-bound excitons (D0X). Otherwise, as the specimen fabricated at 250℃, the dominated peak exhibited a slight decrease to 3.17 eV, accompanied by transition of 3.06 eV due to Zn vacancy (VZn) acceptor defect. The variation tendencies in the RT-PL peaks described above are found to be in accordance with those of the optical band gap energy of the films estimated from the absorption spectra. All the AZO films fabricated showed good optical transmittance (80%–85%) in the visible spectrum.