新型二维原子晶体材料的生长及光电器件研究

Two-dimensional atomic crystal is a new kind of material which is found in recent years. The crystal and energy band structures are unique with rich and novel physical and chemical properties. So this kind of materials has broad applications in the fields of electronics, optics, mechanics and thermophysics. In this proposal, we aims to solve one of the most challenging problems in the field, namely controllable materials growth, impurity doping and 2-D flexible optoelectronic devices. We will use the molecular beam epitaxy to produce wafer-scale high-quality 2D crystals of WSe2, MoSe2 and ReSe2. Combining with in situ observations, we will explore the nucleation mechanism and the relationship between thickness and energy band structure under the ultra high vacuum environment. And based on this, we will further carry out a series of P type and N type doping in experiments and precisely control the carrier concentration, mobility and resistivity. By mixing W and Mo, it is possible to realize the controllability of the bandgap energy. Finally, the growth of atomic layer thickness of homojunction and heterojunction on a transparent substrate will be conducted to achieve high efficiency of transparent flexible optoelectronic devices, including light-emitting diodes and high-anisotropy photodetectors. The results of this research will lead to the exciting inventions of new-type optoelectronic products based on the two-dimensional atomic crystals, thus providing a solid experimental basis and invaluable experience.

二维原子晶体是近年来发现的一类新材料，晶体和能带结构较为独特，蕴含了丰富而新奇的物理化学性质。因此在电子、光学、机械和热物理学等领域具有广阔的应用前景和研究价值。本课题拟解决二维原子晶体材料领域所关注的焦点和难点问题，即材料的可控生长、掺杂以及二维柔性光电器件。本课题将采用分子束外延技术生长高质量二维晶体WSe2、MoSe2和ReSe2。利用超高真空环境、可控生长、可掺杂性等诸多优点，结合原位观察探索二维原子晶体的形核机理及厚度与能带结构的关系，实现大尺度的原子层生长。并在此基础上，开展一系列P型和N型掺杂，精确控制载流子浓度、迁移率以及电阻率。利用W和Mo的混合生长，实现禁带宽度的可控性。最终，本课题将在透明柔性衬底生长原子层厚度的同质和异质结结构，实现高效率的透明柔性光电器件，包括发光二极管和各向异性光探测器。本课题的成果也将为实现令人激动的下一代基于二维原子晶体的新型光电产品提供基础

伴随着石墨烯的巨大研究热潮，新型的二维层状化合物引起了物理、化学、材料、电子等众多领域研究人员的广泛关注。这些化合物包括过渡金属硫化物、硒化物等所形成的二维材料。由于其不同的成分、晶体结构和能带结构，这些二维晶体材料拥有石墨烯所不具备的物理、化学特性，为新物理现象的发现提供了广阔的空间。项目负责人在该项目的支持下，实现了二维原子晶体的分子束外延生长和光电器件的制备,在二维光电探测器研究中取得一定进展：1）研制出一种基于二维范德华异质PN结16×1阵列探测器，并对阵列探测器进行了双波段（可见和短波红外）成像演示，展示了这种双波段二维异质PN结光电探测器具有智能识别目标的能力；2）利用分子束外延生长了大量宽波段二维材料，包括硒化镓、碲化镓、硒碲化镓合金、硒化铟薄膜，样品室温迁移率为30-110 cm2/Vs，对样品进行了0.4-3微米波段的探测和吸收谱测量。利用化学气相沉积法在二氧化硅衬底上外延生长了高质量的新型二维材料二硒化铼（ReSe2）；样品迁移率室温约为10-30 cm2/Vs。实现两英寸二维原子晶体薄膜砷化镉的制备,室温迁移率达到9607 cm2/Vs, 低温迁移率达到12875 cm2/Vs，本征载流子浓度1×1011cm-2；3）利用分子束外延生长了PtSe2与GaN的异质结,并测试了其光电特性，该器件对可见光、红外都有很好的响应。探索了碲化银二维材料，发现其具有超高的迁移率，数值可以达到30万，是目前所有拓扑绝缘体体系中最高的，并且发现了很强的圆偏振光伏效应。在国际重要期刊Nature, Nature Materials, Nature Communications，Advanced Materials, ACS Photonics上发表10篇论文（通讯作者）。在二维光电领域产生了一定的影响力，为二维材料在光电探测领域的进一步发展奠定了基础。