Computational design and fabrication of novel functional materials based on tin oxide

采用理论和实验相结合的方法，探索了二氧化锡(SnO2)的新型气敏和p型导电特性。将基于第一性原理投影增广波方法的声子计算、团簇展开技术和蒙特卡罗模拟相结合，发展了一种预测给定气压和温度下的性质的计算方法。结果表明，用这种方法可以很好地再现二元和三元氧化物体系的相变行为和相界。应用于分子在SnO_2表面的吸附，发现吸附能显著地依赖于表面平面和原子结构。它对周围的大气和温度也有很强的依赖性。在此基础上，提出了设计具有优良传感性能的表面结构的指导思想，并对SnO_2中的各种掺杂进行了计算，以考察其潜在的p型电导。大量掺杂与锡有较大尺寸失配的杂质会导致在带隙中形成杂质诱导带。提出了通过控制杂质带来改变电导率的方法。在理论预测的基础上，进行了掺杂SnO_2薄膜的脉冲激光沉积。

Novel gas sensing and p-type conducting properties of tin dioxide (SnO_2) have been explored using a combined theoretical and experimental approach. A computational method to predict the properties under a given gas pressure and temperature has been developed, by combining phonon calculation based on first-principles projector augmented wave method, cluster expansion technique, and Monte Carlo simulation. It is demonstrated that using this approach phase transition behaviors and phase boundaries are well reproduced for binary and ternary oxide systems. Appling to molecule adsorption on SnO_2 surfaces, adsorption energy is shown to significantly depend on surface planes and atomic structures. It also has a strong dependence on ambient atmosphere and temperature. Based on the results, a guideline for the design of surface structures with superb sensing properties is suggested.Calculations have been conducted as well for various dopants in SnO_2 in order to examine its potential p-type conductivity. A heavy doping of impurities having a large size mismatch with Sn results in the formation of impurity-induced bands in the band gap. It is suggested that the conductivity can be altered by controlling the impurity bands. Pulsed laser deposition of doped SnO_2 films has been made on the basis of the theoretical prediction.