Study on the stress generation during gel/ceramic thin film conversion

1.采用溶胶-凝胶法在硅片上制备了二氧化硅和二氧化钛凝胶膜。在高达800℃的红外炉中恒速加热凝胶膜，并用光学显微镜进行原位观察。发现裂纹发生在升温阶段，且裂纹起始温度低于结晶温度。结果表明，BaTiO_3薄膜的开裂起始温度随初始膜厚的增加和升温速率的降低而降低。2.以含聚乙烯吡咯烷酮(PVP)的醇盐溶液为镀膜液，采用溶胶-凝胶浸渍镀膜法在石英玻璃和氧化镁单晶衬底上制备了BaTiO_3薄膜。扫描电子显微镜观察表明，沉积在石英玻璃衬底上的薄膜具有沿晶界扩展的微裂纹。另一方面，在氧化镁单晶衬底上沉积的薄膜没有发现微裂纹，微裂纹观察到了…更多的二氧化钛薄膜是由薄膜中的拉应力形成的，这被认为是薄膜与衬底之间热膨胀系数失配的结果。3以含有二乙醇胺、乙酰丙酮或醋酸的醇盐溶液为络合剂，采用溶胶凝胶法在石英玻璃衬底上沉积了二氧化钛薄膜。通过测量衬底弯曲来测量烧结膜中的应力，以及络合剂对应力的影响。应力是拉伸的，按醋酸、乙酰丙酮和二乙醇胺的顺序递增。通过薄膜致密化程度的不同来解释络合剂对应力的影响。4以醇盐或含PVP的金属盐溶液为镀膜液，在石英玻璃衬底上制备了BaTiO_3、Fe_2O_3和PZT薄膜。在溶液中加入PVP，BaTiO_3、Fe_2O_3和PZT薄膜的最大摩尔比分别为PVP/Ti(OC_3H_7^I)_4=0.5，PVP/Fe(NO_3)_3=O和PVP/(Ti(OC_3H_7^I)_4+Zr(OC_3H_7^n)_4)。较少

1 Silica and titania gel films were deposited on silicon wafers by sol-gel method using alkoxide-derived sols as the coating solutions. The gel films were heated at constant rates in an infrared furnace up to 800℃, and in situ observation was made using an optical microscope. The cracking was found to occur during the heating-up stage, and the cracking onset temperature was lower than that of crystallization. The cracking onset temperatures were found to decrease with increasing initial film thickness and with decreasing heating rate.2 BaTiO_3 thin films were deposited on silica glass and MgO single crystal substrates by sol-gel dip-coating using an alkoxide solutions containing polyvinylpyrrolidone (PVP) as the coating solution. SEM observation revealed that the fihns deposited on the silica glass substrates have microcracks propagating along grain boundaries. On the other hand, no microcracks were found on the films deposited on the MgO single crystal substrates, The microcracks obse … More ived are supposed to be formed by tensile stress in films, which is thought to be generated as a result of the thermal expansion coefficient mismatch between the film and the substrates.3 Titania thin fihns were deposited on silica glass substrates by sol-gel method using alkoxide solutions containing diethanolamine, acetylacetone or acetic acid as the chelating agents. The stress in the fired films were measured by measuring the substrate bending, and the effect of the chelating agent on the stress. The stress was tensile, increasing in the order of acetic acid < acetylacetone < diethanolarnine. The effect of the chelating agent on the stress was interpreted in terms of the difference in the degree of film densification.4 BaTiO_3, Fe_2O_3 and PZT thin films were deposited on silica glass substrates using alkoxide or metal salt solutions containing PVP as the coating solutions. The critical thickness, the maximum thickness achievable without cracking via single-step deposition was found to increase by incorporating PVP in solutions, showing maximum around mole ratios of PVP/Ti(OC_3H_7^i)_4 = 0.5, PVP/Fe(N0_3)_3 = O and PVP/ (Ti(OC_3H_7^i)_4 + Zr(OC_3H_7^n)_4) for BaTiO_3, Fe_2O_3 and PZT films, respectively. Less