表面化学吸附对氧化物异质结界面二维电子气的调控

The hetrojunction metal oxide structure LaAlO3(LAO)/SrTiO3(STO) has attracted a lot of interest because of the 2D free electron gas at the interface, which has been found to have attrative properties like: metal-insulator transistion, superconducting, ferromagnetic, et.al. People have tried to use different methods to realize the quantum control of the 2D electron gas. We propose to investigate the interaction between the 2D interfacial electron gas with the chemical adsorption using first principles calculations. The proposed research includes: 1. Investigate how the chemical adsorption induced charge transfer and polar distortion affect the 2D electron gas, and try to understand the general mechanism of the chemical adsorption effects. 2. Investigate how the adsorption pattern affect the pattern of the 2D electron gas. 3. Investigate how the 2D electron gas affect the chemical adsorption and the chemical reaction on the surface. 4. Investigate how the O vacancies affect the surface chemical adsorption.Through our investigation, we wish we could understand the role of chemical adsorption on the quantum control of 2D interfacial electron gas in LAO/STO hetrojunction, and put some insights into the applications of LAO/STO hetrojunction in chemical science.

氧化物异质结体系LaAlO3（LAO）/SrTiO3（STO）的界面二维自由电子气存在金属-绝缘体相变、超导、铁磁等一系列新奇的量子性质，人们也尝试用各种手段调控该体系的界面二维自由电子气。申请人计划利用第一性计算原理研究化学吸附对LAO/STO界面二维自由电子气的调控，并对界面二维自由电子气对表面化学吸附及化学反应的影响作出探索。研究内容包括：1、研究电荷转移及极性形变效应对界面二维自由电子气的影响，理解化学吸附对界面二维电子气作用的机理；2、表面分子/原子有序排列对界面二维自由电子气的调控；3、界面二维自由电子气对表面吸附及化学反应的影响；4、O缺陷对LAO/STO体系表面吸附的影响。我们期待通过我们的研究理解化学吸附对LAO/STO界面二维电子气的影响，从理论上给出利用化学吸附调控界面二维自由电子气的依据，为LAO/STO体系在化学领域的应用做出探索。

本项目的主要研究围绕极性-非极性氧化物异质结LaAlO3/SrTiO3（LAO/STO）进行，采用第一性原理计算方法进行了系统的研究。首先利用STO/LAO/STO异质结体系设计了新型的光催化材料，可以提高光吸收效率，并同时有效分离载流子；其次，我们探讨了该异质结在应力作用下的铁电性质，并通过这种铁电性质可以有效调控异质结界面的二维电子气；随后，我们研究了该异质结内内建电场对表面吸附H2O分子的湿电子态的调控。除此之外，我们还将研究对象扩展到其他异质结体系，如MoS2/WS2体系，研究了激发态载流子的超快动力学过程。在本项目的支持下共发表SCI 论文10 篇，其中Nat. Commun. 1篇，Nano Lett. 1篇，J. Phys. Chem. Lett. 1篇，Phys. Rev. B 1篇，Nanoscale 2 篇, 在国际上取得了一定的学术影响。