- 學位論文
以熱處理與低溫雷射處理溶膠凝膠法製備之ITO透明導電膜特性分析及研究
Characterization of Thermally Cured and Laser Cured Sol-gel ITO Thin Films
摘要
本論文探討高溫熱處理與雷射處理之透明導電ITO薄膜的特性。ITO薄膜以溶膠凝膠(sol-gel)法所製備，實驗使用無水氯化銦與四氯化錫做為前驅物，無水氯化銦溶於乙醯丙酮中，並於迴流裝置下加熱至70度持溫3小時，摻雜適量氯化錫溶於酒精溶劑中，並與氯化銦溶液待室溫下均勻混合，完成溶膠凝膠前驅液(precursor solution)的製備。藉由改善製程熱處理的條件，諸如延長前驅膜的加熱乾燥時間、氮氣還原退火、紫外光處理，可得到熱處理的ITO膜最佳電阻率為7.88×10-3Ω-cm及對應的最大載子濃度6.836×1020 cm-3；在可見光波段的平均穿透率達88%。 本論文亦利用UV固態雷射(波長355 nm)退火技術為首要的嘗試。9.09 at.%錫摻雜濃度的前驅液以浸沾法鍍在玻璃基板上，之後置於烘箱中乾燥持溫260度5小時，重複以上浸沾乾燥過程3次，以完成前驅膜的製作。以900 mJ/cm2強度雷射處理的ITO膜呈現最低電阻率5.37×10-2Ω-cm及其對應的最大載子濃度為6×1019 cm-3；在可見光波段的平均穿透率達78%以上。高比例的錫含量(34.3~19.4 at.%)被發現在雷射處理的ITO膜中，然而熱處理的ITO膜僅7.1 at.%錫含量，過高的錫含量會形成不利於導電的錫類複合物。經計算，雷射處理的ITO膜中性散射中心濃度(1.679×1021 cm-3 ~5.925×1021 cm-3)遠大於熱處理ITO膜的結果(5.748×1020 cm-3)。
並列摘要
ITO thin films were deposited on Corning Eagle 2000 glass substrates using anhydrous indium trichloride dissolved in acetylacetone, followed by a refluxing process at 70 ºC for 3 hours and then mixed with tin chloride dissolved in ethanol. By modifying the thermal processes such as prolong preheating duration, introducing post-annealing in reduced atmosphere or ultraviolet illumination, ITO thin films with a minimum resistivity of 7.88×10-3Ω-cm and the corresponding maximum concentration of 6.836×1020 cm-3 by single spin coating were obtained. The average transmittance of thermally cured ITO thin films in the visible light range was above 88%. This study also demonstrated the feasibility of an ultra low temperature (260 oC) ITO sol-gel process by 355 nm solid-state UV lasers. With the 9.09 at.% Sn dopant precursor solution, the optimized process was to preheat the triple dip-coated films at 260 oC for 5 hours, followed by laser irradiation with the fluence of 900 mJ/cm2. The minimum resistivity was 5.37×10-2Ω-cm with activated carrier concentrations of 6×1019 cm-3. The optical transmittances were comparable to those of sol-gel derived ITO thin films by thermal curing (average ~78 %; cf. the thermally cured film 79 %). An extraordinarily high tin element compositions, decreased from 34.3 to 19.4 at.% as laser fluences increased from 700 mJ/cm2 to 1000 mJ/cm2, were presented in the laser cured ITO thin films. In 500 oC thermally cured ITO thin films, only 7.1 at.% tin ratio was detected. Excess Sn ions would form complex defects by Sn (Ⅳ) and Sn (Ⅱ) which were unfavorable to electrical conduction. The calculated density of neutral scattering centers Nn ranged between 1.679×1021 cm-3 and 5.925×1021 cm-3 was nearly one order of magnitude lager than 5.748×1020 cm-3 with thermally cured ones.