溶胶-凝胶-蒸镀法制备高性能FTO薄膜

以SnCl_4·5H_2O为锡源,SnF_2为氟源,采用溶胶-凝胶-蒸镀法制备F掺杂的SnO_2透明导电氧化物薄膜(FTO薄膜).通过正交实验研究确定最佳反应温度、反应时间和蒸镀温度等制备条件.主要研究元素F的掺杂和膜的结构对FTO薄膜性能的影响,并采用傅里叶变换红外光谱仪、热重-差热分析、X射线衍射、高分辨透射电子显微镜和扫描电子显微镜等进行样品的性能表征.研究结果表明,当反应温度50?C、反应时间5 h、烧结(蒸镀)温度600?C、镀膜次数1次、而F/Sn=14 mol%时,FTO薄膜性能指数ΦTC最大,综合光电性能最优,表面电阻为14.7?·cm-1,平均透光率为74.4%.FTO薄膜内颗粒的平均粒径为20 nm,呈四方金红石型结构,F的掺入替代了部分的O,形成了SnO_(2-x)F_x晶体结构.F的掺杂量是影响FTO薄膜的主要因素,F过多或过少均不利于SnO_(2-x)F_x晶体的生长;FTO薄膜的结构、颗粒形状、大小等三维信息也是影响薄膜性能的因素,主要表现为分形维数越小,薄膜表面越平整,势垒越低,导电性能越好.

The preparation of high-performance FTO thin film by Sol-Gel-evaporation method

The purpose of this work is to prepare the high-performance transparent conductive thin films of fluorine-doped tin oxide (FTO) by using a simple technological process. The FTO thin films are formed in the period of calcination process combined with the advantages of sol-gel method and chemical vapor deposition method, which not only avoids the shortcomings of film cracking in sol-gel coating process, but also reduces the cumbersome traditional dip-coating method and spin-coating method on glass substrates, largely simplifying process and cutting costs. The FTO thin films are deposited onto glass substrates by the sol-gel-evaporation method with SnCl₄·5H₂O as a tin source, and SnF₂ as a fluorine source. The effects of F-doping content and the structure of the film on the properties of FTO film are mainly studied. The prepared films are characterized by IR, DTA-TG, XRD, TEM, SEM, etc. The results show that the maximum performance index (Φ_TC) of the FTO film, the lowest surface resistance of 14.7 Ω·cm^-1, and the average light transmittance of 74.4% when F/Sn=14 mol% are achieved under the conditions of the reaction temperature of 50 ℃, the reaction time of 5 h, sintering or evaporation temperature of 600 ℃ for 2 h. It is indicated that part of O is replaced by F, and SnO_2-xF_x crystal structure is formed. It reveals that the crystal structure is polycrystalline and has a preferential orientation along the (110) direction and the spacing between the lattice fringes is about 0.33 nm in the FTO film. And the particles in the FTO film present a tetragonal rutile phase with an average size of 20 nm and a film thickness of 1.22 μm. Fractal dimension of image by dealing with SEM image of FTO film shows that the surface resistance decreases with the decreasing of fractal dimension, which in fact critically demonstrates the lower barrier. The lower the barrier, the smoother the surface of the thin films is. So the fluorine concentration is the main factor affecting the properties of FTO thin film. Too much or too less fluorine is not conducive to the growths of SnO_2-xF_x crystals. And then the three-dimensional information such as structure, particle shape and size of the FTO thin film is also the factor influencing the FTO film properties. The analysis of SEM shows that the surface morphology of the thin film is in the pyramid-shaped structure, which is beneficial to improving the utilization of photons, and well used in the optoelectronic devices.