ITO透明导电薄膜的溶胶凝胶法制备及工艺研究

【作者】 李晶；

【导师】 陈世柱；

【作者基本信息】 中南大学 ， 材料学， 2004， 硕士

【摘要】 本研究以五水硝酸铟为源物质，以乙酰丙酮为溶剂，以无水氯化锡为掺杂剂，采用溶胶凝胶工艺，用提拉法在普通玻璃和石英玻璃基体上制备了ITO透明导电薄膜。本试验采用XRD、SEM、FT-IR、四探针电阻率仪、紫外分光光度计等仪器对ITO透明导电薄膜的物相、表面结构、微区形貌和物理性能进行了测定；通过DTA-TG对薄膜从凝胶态向结晶态的转化过程进行了测定和分析；此外本试验重点研究了在ITO透明导电薄膜的溶胶凝胶法制备过程中，不同试验条件（提拉次数、提拉速度、热处理温度、冷却速度、不同玻璃基体）对薄膜的基本性质（导电性能和透光率）的影响；分析了试验现象，优化了试验条件。 本研究结果表明：以五水硝酸铟为源物质，以乙酰丙酮为溶剂，以无水氯化锡为掺杂剂、采用溶胶凝胶工艺在玻璃基体上或在石英基体上制备ITO透明导电薄膜是完全可行的。所制备的ITO薄膜的晶体结构为立方锰铁矿结构，[111]为明显的择优取向，掺杂的Sn已完全溶解在In₂O₃的晶格中，看不到SnO或SnO₂的特征谱线；ITO薄膜在热处理过程中脱去结晶水和有机组份，由凝胶态转化为结晶态，当温度超过530℃时，转化基本完成。 在石英基体上经5次镀膜后的ITO薄膜厚度小于150nm，与基体结合良好，表面无空洞、气泡等宏观缺陷。ITO薄膜的微观结构呈现为由尺寸为几十个纳米的球形颗粒堆积而成的多孔结构。不同热处理制度可以明显改变ITO薄膜的微观形貌，包括颗粒和孔隙的尺寸以及第二相的种类与分布。经5次镀膜后的ITO薄膜方电阻可达110Ω／□，电阻率为1.65×10^-2Ω·cm。在330nm-1000nm范围内，最大可见光透过率达90％以上。 试验表明：ITO薄膜的方电阻开始随In³⁺的增加而降低，达到特定值后逐渐升高，当In³⁺过量时会加速溶胶的水解过程，降低透光率。ITO薄膜的方电阻随Sn掺杂量的增加逐渐达到最小值，再增加Sn掺杂量薄膜的方电阻略有上升的趋势。ITO薄膜的方电阻随提拉次数的增加而降低，在3-21cm·min^-1的提拉速度范围内，薄膜提拉速度对薄膜导电性能影响不大。ITO薄膜的方电阻随热处理温度升高而降低，在600℃左右达到最小值；当对ITO薄膜进行快速冷却时，薄膜的方电阻显著下降。不同玻璃基体对薄膜方电阻的影响较大，但当镀层数增加时，这种影响逐渐变小。 ITO薄膜的透光率随镀膜层数的增加而减少，薄膜随厚度的增加对光的吸收逐渐增加。当ITO薄膜处于干凝胶状态时具有最高的透光率，在薄膜从凝胶态向结晶态转变后透光率有所降低，并且在热处理过程中随热处理温度的增加而缓第一章文献综述慢增加。Sn掺杂量对薄膜透光率的影响不大，随Sn掺杂量增加薄膜的透光率呈缓慢降低的趋势。ITO薄膜在进行快速冷却后具有较低的透光率，该现象在热处理温度较高和较低时表现的都不明显。产生该现象的原因是由于不同冷却速度影响了薄膜的晶粒度和表面粗糙度。更多还原

【Abstract】 In this experiment ,Indium tin oxide (ITO)film which is highly conductive and transparent to visible light has been prepared by sol-gel dip-coating technique and In(NO3) was chose as raw material, acetylacetone as solvent, SnCl4 was chose as dopant. The structure properties and the physical properties (electrical resistance and transmittance) of the film were investigated by XRD, SEM , IR four-probe method and UV-VIS spectrometer. The process that the film was transformed from amorphous state to the polycrystalline structure has been determined by the DTA-TG technique. In addition, The influence of different technological conditions (dipping times and speed, annealing temperature, cooling speed and matrix materials) on the film properties have been investigated in detail .The experimental results is discussed and the experimental conditions i s optimized.The experimental results indicate the possibility to prepare ITO conductive and transparent film by the sol -gel dipping method .ITO film have the polycrystalline cubic bixbyite In2O3 structure, but the result that no XRD pattern of Sn compound (SnO or SnO2) has been determined shows the fact that a solution of Sn in In2O3 was formed .the transformation from the amorphous state to the polycrystalline state was finished completely at 600℃.The thickness after 5 times dip coating is less than 150nm,the desirable connection with matrix can be determined .Meanwhile ,few macro defects such as holes can be observed .The micro structure of this film is the porous structure which is accumulated by many spherical particles .the micro structure of film ,including the size and distribution of second phase, is obviously changed by different annealing techniques .The minimum of sheet resistance is about 110 Ω□,the minimum specific resistance of can reach 1.65 X 10-2 Ω·cm. When the wavelength of visible light rang from 400nm to l000nm, the 90% maximum of transmittance can be reached.,The experimental results indicates: At the beginning, the sheet resistance of ITO film decreased with the increase of [ In.] But it increased when the certain point of [In] has been surpassed. Superfluous [In] may contribute the process of hydrolysis and reduce the transmittance of the film .The maximum of the sheet resistance can be reached.The doping speed has little influence on the conductivity of film and the sheet resistance decreased with the increase of annealing temperature, and the minimum ofresistance of ITO film can be abtained when the rapid cooling process is conducted .In the experiment. The different properties of matrix have obvious influence on the sheet resistance of ITO film .But such influence may decrease with the increase of coating layers.With the increase of coating times and the thickness of film ,its transmittance reduced because of the increase of the absorption to visible light .When ITO film remains amorphous state ,It has the maximum of transmittance .the transformation from the amorphous state to the polycrystalline may lead to the decrease of transmittance ,but with the increase of annealing temperature ,the transmittance of the film may increase slowly. Doped [Sn] show little influence on the transmittance of ITO film. And it can be found that the increase of [Sn] may lead the slight decline of transmittance of film. After the process of rapid cooling, ITO film shows the relative low transmittance ,but such phenomenon is not very obvious when the annealing temperature is relative high or low, the decrease of transmittance is due to the fact that the different cooling speeds changed the grain size and the rough state of ITO film.更多还原