【作者】 周艳军；

【导师】 王玉林；

【作者基本信息】 天津大学 ， 材料学， 2010， 博士

【摘要】 TiO₂作为一种廉价、无毒、化学性质稳定的半导体,目前已成为研究最为广泛的太阳能电池用材料之一。但TiO₂禁带宽度较宽,对太阳能的利用率很低,限制了其在太阳能领域的实际应用。因此对TiO₂进行各种掺杂,以提高其对太阳光的利用率。本文分别采用溶胶-凝胶法和磁控溅射法制备了纯TiO₂薄膜,并采用溶胶-凝胶法和离子注入技术对TiO₂薄膜进行改性研究。在溶胶-凝胶法制备TiO₂薄膜过程中将Ge掺入TiO₂薄膜;在溶胶-凝胶法制备的TiO₂薄膜中,用离子注入技术进行了Fe、Cr的单独注入以及复合注入;在磁控溅射法制备的TiO₂薄膜中,分别进行Ge、Si的单独和复合注入。考察了掺杂方式和掺杂离子对薄膜表面形貌、结晶、表面化学态和光学性能的影响,结果如下。XRD及XPS的研究结果表明,溶胶凝胶法和磁控溅射制备的TiO₂薄膜为锐钛矿型;但薄膜的表面化学态及价键状态有所不同,最终导致两者光性能的差异。溶胶的配比对薄膜质量有影响。采用溶胶-凝胶法对TiO₂进行Ge掺杂及还原处理,薄膜产生了一定红移,掺杂Ge:Ti = 3:7的薄膜红移显著,同时聚乙二醇的加入有利于薄膜红移。溶胶凝胶法在不同室温下制备薄膜结晶性、Ge存在方式、紫外-可见吸收不同。室温22℃条件下制备的薄膜及其中Ge的结晶性很好;XPS分析表明,Ge大部分以单质形式存在;18℃条件下掺杂薄膜结晶性差,Ge主要以氧化锗形式存在。Fe、Cr离子复合注入后,薄膜的结晶性变差;XPS分析结果显示,Fe、Cr分别以单质和氧化物形式存在;光学性能较单独注入Fe的有所下降。分析表明,两种离子的相互作用最终使得薄膜中有效离子浓度降低,Cr的存在使Fe得红移效果降低。与Fe、Cr离子复合注入不同,在磁控溅射法制备的TiO₂薄膜中,Si、Ge复合注入使得薄膜的红移效果显著,但结晶性变差;XPS分析Ge、Si表明;Si以氧化态存在,Ge以单质存在,两种离子的相互作用,使复合注入的薄膜光学性能有大幅度提高。以上研究结果为促进制备对可见光敏感的TiO₂薄膜的研究提供了有价值的参考依据。更多还原

【Abstract】 As a low-cost, non-toxic and chemically stable semiconductor, TiO₂ has been regarded as one of the most extensively investigated materials in the filed of solar cells. However, the inactivity in the visible light region limits the practical applications of TiO₂. Therefore, different elements were doped into TiO₂ to improve the inherently low efficiency of TiO₂ in harvesting sun light by shifting its spectral response into visible light range.In this thesis, pristine TiO₂ thin films were synthesized by sol-gel method and magnetron sputtering systems. Modification of the films was performed by sol-gel and ion implantation methods respectively. Ge was doped into films of TiO₂ by sol-gel method. Fe, Cr ions were implanted into the films by sol-gel method. Fe, Cr were implanted separately and then co-implanted. Ge, Si implantation were carried out on the films deposited by middle frequency magnetron sputtering system. The effect of the doping methods and different ions were investigated on the surface morphology, crystallization, surface chemical states and optical characterization.According to XRD and XPS, TiO₂ films obtained by sol-gel method and magnetron sputtering systems were anatase, and the different optical properties resulted from the difference of surface chemical states and bonds of these two kinds of films. The proportion of sol materials affected the quality of films.Certain optical property improvement was achieved by Ge doped TiO₂ films synthesized by sol-gel method and deoxidization. In comparison to the pristine TiO₂ films, the absorption edge of the doped films （Ge: Ti = 3: 7） had distinct red shife, and the same result appeared on account of polyethyleneglycol joined. The doped films had high crystallinity at atmosphere temperature of 22℃, and the majority of Ge was element based on XPS spectra. In contrast the doped films had low crystallinity at atmosphere temperature of 18℃, and Ge existed mostly in the form of oxides based on XPS spectra.Fe/Cr co-implanted films showed lower crystallinity than the pure TiO₂ films, and in the co-doped films Fe and Cr existed in the form of element and oxides based on XPS spectra. After the implantation of Fe and Cr, optical property of the film was worse than when Fe was doped. The interaction between these two kinds of ions decreased the efficient implanted ions, which made the absorption of the co-implanted films worse than when Fe doped because of the existence of Cr.Unlike the Fe/Cr co-implanted films, optical property of the Ge/Si co-implanted films was improved significantly. Ge and Si ions could promote the optical behavior of the films. However, crystallinity of the flims was destroyed because of the implantation. Si existed in the form of oxides, and Ge existed in the form of element and oxides based on XPS spectra. The interaction between Ge and Si was beneficial to improve the optical property of TiO₂ films.These results provide a valuable reference for the further investigation of visible light sensitive TiO₂ thin films.更多还原