Improvement of functionality of sol-gel-derived silica glass thin films by tailoring their nanostructure at low heat-treatment temperature.

目前，人们越来越强烈地要求在低于500 ℃的温度下，以低成本和不复杂的工艺在半导体、塑料和金属基底上制备二氧化硅玻璃薄膜涂层。溶胶-凝胶法已被开发用于该目的，但仍需要在600-800 ℃下热处理以将二氧化硅凝胶膜转化为致密的玻璃膜。通过X-射线衍射分析方法对烷氧基衍生的硅胶在加热时的纳米结构变化的检测，我们发现，在凝胶中占主导地位的是4重硅氧烷环单元，并且在600-800 ℃下的热处理对于将凝胶转变为玻璃是必不可少的。然后，我们发明了获得由6重硅氧烷环组成的硅胶的方法。然而，由此获得的玻璃涂层膜在500 ℃以下仍然是多孔的。通过在空气中在450 ℃下热处理，全氢聚硅氮烷（PHPS）得到致密的二氧化硅玻璃涂层膜。在本研究中发现，Si-H键保持高达450 ℃使玻璃化温度难以降低。在此基础上，我们又合成了Si-H键在450 ℃以下容易脱除的新型PHPS，得到了SiO2玻璃薄膜，但原料价格昂贵，最后我们尝试将两种方法联合收割机结合起来。以烷氧基衍生的六重环硅氧烷低聚物与PHPS按9：1的比例混合作为原料制备二氧化硅玻璃涂层，是一种非常有前景的低成本、简便地制备450 ℃以下的二氧化硅玻璃涂层的方法。

Establishment of technique to produce silica glass thin film coating on semiconductor, plastics and metal substrates at temperatures below 500ﾟC in low cost and without complicated processes is nowadays more and more strongly demanded.The sol-gel method has been developed for that purpose, but the heat-treatment at 600-800ﾟC is still required for transforming silica gel films to dense glass films, In the present study, we found through the examination of nano-structure change of the alkoxy-derived silica gels on heating by X-ray diffraction analysis method that 4-fold sioxane ring units are prevailing in the gels, and the heat-treatment at 600-800ﾟC is indispensable for changing gels to glasses. Then we invented the method by which silica gels consisting of 6-fold siloxane rings are obtainable. The glass coating films thus obtained, however, were still porous below 500ﾟC.Perhydropolysilazane (PHPS) gives dense silica glass coating film by the heat-treatment at 450ﾟC in the air. It was found in the present study that Si-H bonds remaining up to 450ﾟC make difficult the lowering of glassification temperature. Then novel PHPS from which Si-H bonds are easily removed on heating was synthesized to obtain silica glass films below 450ﾟC.However, the raw materials are still expensive.Finally we tried to combine above two methods. The combination, namely the preparation of silica glass coating by using the mixture of alkoxy-derived sioxane oligomers consisting of 6-fold rings and PHPS as raw materials in the ratio of 9 to 1 was found to be very prospective for making silica glass coatings below 450ﾟC in low cost and with ease.