基于层数可控石墨烯的应变调控及其物性研究

Graphene has many promising properties, such as the metal conduction without electronical limitation, half-integer quantum Hall effect at room temperature, etc. Currently, the graphene physical properties exploration is still being in-depth carried out. Because graphene is only one atom to a few atom thick, it is highly susceptible to external influences, including the effects of mechanical deformation, which provides us with strains to regulate the physical properties of graphene at attractive prospect. There are already some studies reported that graphene has unique characteristics under condition of uniaxial deformation. We design specific graphene strain loading, so that the strain can be loaded along different crystallographic axes, thereby inducing a relatively strong gauge field, which can be equivalent to a uniform magnetic field of a few dozen to hundreds Teslas. We propose here a practical method to create quantum states in strained graphene, and to study the role of this pseudo-magnetic field on the properties of graphene. Further, we demonstrate graphene bandgap opening by promoting the superlattice structure via strains, which is useful to be applied in high-speed electronic devices. In this project we set out to research on the electron transport theory and the materials science and technology of the strain graphene with controlled layers, and the physical characteristics of the preparated materials. We will engaged in solve the key scientific problems encountered when preparating layer-controlled and strain- tailoring graphene, and exploring the unique physical properties under the pseudo- magnetic field and the enhancement mechanisms.

石墨烯具有许多特异的物理性质,如不受电子限制的金属性导电、室温半整数量子霍尔效应等，对它的特性进行深入探索仍然是当前的研究前沿。由于石墨烯只有一个至数个原子层厚，它极易受到外部影响，包括机械形变的影响，因此可以通过应变来调控石墨烯的物性。已经有一些研究报导了石墨烯在单轴形变作用下的物性。通过设计应变加载方式，使应变沿不同的晶轴方向，由此诱导出了比较强的规范场，可以等效为一个数十至数百特的均匀磁场。本项目提出切合实际的量子态创建方法，并研究这种赝磁场作用下石墨烯的物性。另外，也推广到通过应变超晶格结构来打开石墨烯能隙，使其在高速电子器件中得到应用。本项目以层数可控应变石墨烯电子输运理论、材料科学及制备技术、物理特性为主要研究内容，着重解决层数可控的石墨烯制备与应变剪裁、赝磁场下特异物性及增强机制等关键科学问题。

项目直接在实验上石墨烯的各向异性来自石墨烯晶格本身，是石墨亚原子结构在宏观上的反映，在实验上证实了未掺杂的单层石墨烯的确具有平面各向异性，具有两重对称性，对于器件的制作具有重要的启示和实际意义，制作特殊的光电子器件。通过理论模拟研究4H-SiC MOS界面的调控机理与迁移率影响机制，分别探讨了高场应力下表面粗糙度的散射机制加强，引起场效应迁移率随栅压的升高而降低；高温应力下，表面声子散射机制加强，场效应迁移率和有效迁移率随着栅压的变化趋于稳定；首次在沟槽型MOS电容器中获得其侧壁栅介质的界面态密度，在1250℃下NO退火1小时以上，SiO2/SiC的界面浅态和界面快态密度增大，因而不利于MOSFET沟道迁移率的提升。同时对于具有(112_0)面的侧壁MOS电容，其导带底以下0.3eV的界面态密度降低到1012 cm2•eV-1以下，这比平面型的MOS电容要小，表明SiC UMOSFET具有更高的应用潜力。