二维层状纳米材料表面与界面的太赫兹辐射机理和调控研究

Two-dimensional (2D) layered nanomaterials have rich surface and interface atoms and demonstrate novel optoelectronic properties at the surface and interface. The inter-discipline research of the terahertz (THz) technology and 2D materials has become a new hot research topic in recent years. Our previous studies have found that the THz radiation from the 2D materials are sensitive to the surface and interface properties and the radiation mechanism is different from the traditional materials. Therefore, understanding the mechanism and regulation of THz radiation is the key issue to the development of a new type of THz source in this field. This project intends to construct Van Der Waals surface and interface with steep potential gradient. A new type of THz emission spectroscopy technique with transmission, reflection, polarization, and angle measurement is established. The parameters such as amplitude, phase, and polarization of the THz radiation pulse at the surface and interface of the two dimensional materials will be measured by this technique. Based on the analysis of these measured parameters and the quantum effect etc., we will construct the THz radiation model from 2D materials and clarify the new mechanism of THz radiation. Then, we will study the relationship between the intrinsic stacking, doping, adsorption, external electric and magnetic fields and the THz radiation parameters such as amplitude, phase, polarization, spectral width. From this relationship, a new method for the regulation of THz radiation from the surface and interface of 2D nanomaterials is established. Using this method, the dynamic processes of the carriers, dipoles etc. at the surface and interface of the 2D materials are regulated to achieve the enhancement of new type of 2D THz radiation source. .. This project is the inter-discipline of THz science and nanotechnology. The results from the project are expected to promote the using of THz technology for the study of surface and interface physics of materials and deepen the understanding of the optical physics processes in 2D materials. The output will also provide technical and theoretical support for the development of new-type THz sources and 2D devices based on 2D materials.

二维材料,具有丰富的表界面并展现出新奇的光电特性，它与太赫兹（THz）的交叉研究近年来成为一个新兴的热点。我们前期研究发现其THz辐射对表界面敏感，机理不同于传统材料，所以阐明其THz辐射机理及调控规律是发展新型二维THz源的关键。本项目拟构建具有陡峭势场梯度的新型范德瓦尔斯表界面，建立具备透反射、偏振、角度测量的新型THz发射光谱技术，测定二维材料表界面THz辐射脉冲的振幅、相位、偏振等参数，分析以上参数并考虑量子效应等构建THz辐射物理模型，阐明辐射的机理；研究内在的叠层、掺杂、吸附，外在的电、磁场等调控方法与THz辐射的振幅、相位、偏振、谱宽、辐射角等参数之间的关系，建立调控表界面THz辐射的新方法，进而调控光生载流子、偶极子等动力学过程，以实现提高二维材料THz辐射性能的目标。该研究将促进THz技术用于表界面物理的研究，加深对二维材料光物理过程的理解并推动二维THz源和器件的发展。

二维材料由于层与层之间是范德瓦尔斯相互作用，因此具有陡峭的势场梯度，能够构建新型的范德瓦尔斯表面和界面。太赫兹技术可以对二维材料的表面和界面进行无损表征，同时相辅相成，对于二维材料的研究也可以促进太赫兹功能器件的发展，这些是目前太赫兹和光电功能材料研究的新兴交叉领域。项目首先发展了化学气相和物理气相沉积法制备二维材料及其异质结，其次，自主搭建了具备透射-反射、偏振、角度测量的新型太赫兹发射光谱技术。再次，利用这样的技术，我们发展了二维材料表面和界面太赫兹辐射参数的提取方法，构建了相关的二维材料表面和界面太赫兹发射的物理模型，阐明了二维材料表面和界面太赫兹辐射的机理。研究了光场和偏振等调控方法对于太赫兹表面和界面辐射的调控作用，建立了表面和界面太赫兹辐射的调控新方法，发展了基于二维材料及其异质结的太赫兹发射器和调制器。研究了二维材料中多种新型的物理效应：位移电流效应，注入电流效应，表面场效应、隐藏的自旋极化效应、光牵引效应等。率先提出范德华异质结界面信息提取方法以及异质结非线性光学增强机制，提出双光子吸收引起的高阶位移电流理论。提出太赫兹界面技术和界面物理，获得认可，受邀撰写两篇长篇文章：Terahertz Surface and Interface Emission Spectroscopy For Advanced Materials; Terahertz Interface Physics: From Terahertz Wave Propagation to Terahertz Wave Generation。这些研究成果从理论上和实验上加深了对于二维材料表面和界面处太赫兹辐射规律的认识，为构建基于二维材料的太赫兹器件奠定了基础。项目实施过程中获陕西省自然科学一等奖1次，发表标注基金项目资助号的SCI论文62篇，其中一区论文20篇，二区论文42篇，申请国家发明专利6项，4项授权。应邀为Taylor & Francis出版社撰写书目章节1篇，受邀做国内外学术会议报告30余次，邀请国内外专家到访指导10次，与国内外同行进行了深入的学术交流。项目培养硕士和博士毕业研究生9人，1人获校优秀博士学位论文，9人获国家奖学金，1人获陕西省第五届研究生创新成果理科一等奖。