基于应变二维晶体的新型同质结

Two-dimensional (2D) crystals represent a class of new quantum materials with extraordinary physical properties. Due to the remarkable stability under very large strain, their properties exhibit significant strain modulation effects. On the basis of our recent research results, we propose to investigate a novel type of homojunctions, named as 2D strain homojunctions. Different from the traditional semiconductor homojunctions obtained by doping, a 2D strain homojuction is formed by a 2D crystal with a strained part and non-strained part. Focusing on graphene, semiconducting 2D crystals of transition metal chalcogenides and phosphorene, we will use first-principles computational methods and bands-alignment theory to design the physical models of the 2D strain homojuctions and uncover the modulation effects of strain on the band structure, charge transfer, build-in electric field, spin distribution of the homojuctions. In addition, we will take the V2VI3 topological insulator film consisting of a few layers of 2D crystals as an example to investigate the modulation effects of strain in the homojunction on topological surface states by first-principles methods, broadening the applications of strain homojunctions. Because the 2D strain homojuction does not require doing and can perform reversible dynamic modulation, it will have more and important applications than the transitional homojunctions formed by doping.

二维晶体是一大类具有优异物理特性的新颖量子材料，由于其结构能在巨大的应变下保持稳定，其电子能带呈现出显著的应变调制效应。本项目拟在我们近期工作的基础上，研究一类新型同质结，即二维应变同质结。不同于由掺杂得到的传统半导体同质结，二维应变同质结由具有应变区和非应变区的同质二维晶体构成。我们将针对石墨烯、过渡金属二硫族化合物和磷烯二维半导体，以第一性原理计算方法与能带匹配理论相结合的方式，设计二维应变同质结的物理模型，揭示应变同质结中应变对能带结构、电荷转移、内建电场、自旋分布等的调控效应。同时，我们将研究由少数层二维晶体构成的V2VI3拓扑绝缘体薄膜，采用第一性原理计算方法探索应变同质结对拓扑表面态的调控效应，拓展其应用范围。由于二维应变同质结无需掺杂并能进行可逆动态调控，它将比二维掺杂同质结具有更为广泛和重要的应用前景。

二维晶体是一大类具有优异物理特性的新颖量子材料，由于其结构能在巨大的应变下保持稳定，其电子能带呈现出显著的应变调制效应。本项目针对过渡金属硫族化合物、石墨烯、磷烯等单元素二维晶体，主要采用第一性原理计算方法，设计多种二维晶体及其同质结的物理模型，研究了二维晶体以及二维晶体同质结的能带结构、电荷转移、内建电场、谷电子、拓扑表面态等电子性质以及应变调控效应；结合第一性原理计算方法，对气相沉积方法合成的MoTe2二维晶体同质结中界面处的电荷分布特征以及传导规律进行了深入探讨，发现并揭示了该同质结中界面欧姆接触的物理机制；实验上成功合成了多种过渡金属硫族化合物和单元素二维晶体，并对这些二维晶体在应变、在应变以及应变与温度耦合、应变与等离子耦合下的晶体结构与电子性质进行了探讨，积极拓展二维晶体在光电探测器件以及柔性光电子器件中的应用潜力。. 在本项目的资助下，在Physical Review B、Physical Review Applied、Science China Physics、Applied Physics Letters、Nano Research等知名学术期刊上发表SCI论文26篇，其中通讯作者论文17篇。指导研究生获湖南省优秀博士学位论文1篇，获宝钢优秀教师特等奖。研究成果将对发现光电性能优异的二维材料体系，阐明其中的新奇物理效应和机制具有重要的指导意义。