Exploration of photonic electronic magnetic and their mutual functionalities in non-equilibrium and transparent oxide thin films accelerated by parallel epitaxy

自高温超导体发现以来，外延氧化物薄膜的研究得到了迅速发展，其研究领域扩展到铁电、磁性和光子等多功能材料。晶体生长过程的原子尺度控制和异质结构探索了氧化物电子学，其中氧化物半导体在实现常规半导体无法实现的应用方面发挥着重要作用。在本研究计画中，我们将透过平行合成的方法，来研究透明半导体材料如氧化锌和二氧化钛，以提供新颖的光、电、磁功能。这类器件的原型已经被证实为ZnO紫外发光二极管、高迁移率ZnO隐形晶体管、（TiCo）_2磁性隧道结。以下是输出的示例。光子功能1.温度梯度法作为平行外延方法之一，优化了生长条件，制备出世界上最好的本征ZnO.首次采用反复温度调制技术制备了P型ZnO，以促进氮作为受主的掺入和活化.在ZnO pn结中实现了紫外LED。电子功能4.利用模拟器对多晶沟道ZnO薄膜晶体管进行了理论计算，并阐明了影响器件性能的限制因素.在单晶ZnO TFT中实现了200cm2Ns的场效应迁移率。首次在氧化物中观察到量子霍尔效应。磁性功能7.磁光效应和反常霍尔效应证实了TiO_2：Co中载流子的自旋极化性质.第一个以TiO_2：Co为磁性隧道结的宽带隙磁致伸缩器为例进行了自旋注入器件的研究.用第一性原理计算方法研究了TiO_2：Co的电子结构。

After the discovery of high Tc superconductors, the research on epitaxial oxide thin films has been rapidly advanced to extend its research area to versatile functionalities such as ferroelectric, magnetic, and photonic ones. Atomic scale control of crystal growth process and heterostructures explore oxide electronics, among which oxide semiconductors play important role to realize applications that cannot be achieved by conventional semiconductors. In this research program, transparent semiconductors such as ZnO and TiO_2, are examined to donate novel photonic, electronic and magnetic functionalities through efficient parallel synthesis method. Such prototypical devices have been demonstrated as ZnO ultraviolet light emitting diodes, high mobility ZnO invisible transistors, magnetic tunnel junctions of (TiCo)_2. The followings are examples of the output. Photonic Functionality1. Temperature gradient method was developed as one of the parallel epitaxy method to optimize the growth conditions for making world-best intrinsic ZnO.2. P-type ZnO was produced for the first time by developing repeated temperature modulation technique to facilitate the incorporation and activation of nitrogen as acceptors.3. Ultraviolet LED was demonstrated in ZnO pn-junctions. Electronic Functionality4. Polycrystalline channel ZnO thin film transistors were formulated by a simulator and limiting factors of device performance were clarified.5. A field effect mobility of 200cm2Ns was achieved in single crystalline ZnO TFT.6. Quantum Hall effect was observed in oxide for the first time. Magnetic Functionality7. Spin polarized nature of charge carriers in TiO_2: Co was confirmed by magneto-optic and anomalous Hall effects.8. Magnetic tunnel junctions of TiO_2: Co was demonstrated as a first example of spin injection device of wide bandgap magnetic semiconductors.9. Electronic structure of TiO_2: Co was studied by first principle calculation.