Graphene Encapsulated Growth of 2D Materials

非技术描述：该项目探索了使用石墨烯封装生长来形成单层(也称为二维)的传统三维材料，特别关注在紫外线范围内发射光的材料。石墨烯包裹生长过程最初被证明是为了合成二维氮化镓，它涉及生长物种在碳化硅上形成的石墨烯下面的超薄空间内的扩散和反应。这项研究结合了实验研究和分子模拟，旨在加深对合成过程的基本了解，旨在实现更好的控制和可扩展性，并将该技术扩展到其他二维氮化物和氧化物的合成。大面积、均匀和可重复的二维氮化物和氧化物薄膜的实现对量子通信和计算、紫外线发射器和探测器以及高频/高功率电子学等一系列技术产生了影响。这些活动为一名研究生、一名博士后学者和几名本科生提供了合作研究的机会，也吸引了来自代表性不足和经济困难背景的高中生。技术描述：研究重点是在金属有机化学气相沉积环境中通过石墨烯包裹生长合成二维氮化物和氧化物薄膜的缺陷和生长化学的基础研究。实验研究的重点是控制石墨烯层中缺陷的类型和密度，以了解它们对表面化学分析所评估的镓和氮前体的吸附和反应的影响。合作研究使用原子分辨率表征技术，包括扫描隧道显微镜和具有化学分析的像差校正扫描电子显微镜，以提供关于缺陷以及合成材料的结构和化学的详细见解。这些实验得到了原子尺度模拟的支持，这些模拟用于研究前体在石墨烯表面的热分解和吸附，物种在石墨烯层上和通过石墨烯层的传输，以及导致氮化镓形成的亚表面反应。为了实现这些模拟，研究小组将现有的ReaxFF参数集扩展到镓/石墨烯系统，并将这些参数集与分子动力学和蒙特卡罗技术结合使用，以研究化学和扩散事件。这些研究还将该技术扩展到研究其他二维氮化物和氧化物的合成。该项目的总体目标是开发石墨烯封装生长作为合成新型二维材料的通用平台。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical description: The project explores the use of graphene encapsulated growth for the formation of single layer (also known as two dimensional) of traditionally three dimensional materials with a specific focus on materials that emit light in the ultraviolet range. The graphene encapsulated growth process, which was initially demonstrated for the synthesis of two dimensional gallium nitride, involves the diffusion and reaction of growth species within the ultrathin space that is present beneath graphene formed on silicon carbide. The research, which combines both experimental studies and molecular simulations, is aimed at developing a fundamental understanding of the synthesis process, aiming to achieve improved control and scalability, as well as to expand the technique to the synthesis of other two dimensional nitrides and oxides. The realization of large area, uniform and reproducible two dimensional nitride and oxide films impacts a range of technologies including quantum communication and computing, ultraviolet emitters and detectors and high frequency/high power electronics. The activities provide collaborative research opportunities for a graduate student, a postdoctoral scholar and several undergraduate students and also engages high school students from underrepresented groups and economically disadvantaged backgrounds.Technical description: The research focuses on fundamental studies of defects and growth chemistry relevant to the synthesis of two dimensional nitride and oxide films via graphene encapsulated growth within a metalorganic chemical vapor deposition environment. Experimental studies focus on controlling the type and density of defects in the graphene layer in order to understand their impact on the adsorption and reaction of gallium and nitrogen precursors as assessed by surface chemical analysis. Collaborative research employs atomic resolution characterization techniques including scanning tunneling microscopy and aberration-corrected scanning transmission electron microscopy with chemical analysis to provide detailed insights on defects and the structure and chemistry of synthesized materials. The experiments are supported by atomistic-scale simulations, which are used to study precursor thermal decomposition and adsorption on the graphene surface, species transport on and through the graphene layer and sub-surface reactions that lead to gallium nitride formation. To enable these simulations, the research team extends existing ReaxFF parameter sets to gallium/graphene systems and uses these, in conjunction with molecular dynamics and Monte Carlo techniques, to study chemical and diffusion events. The studies also extend the technique to investigate the synthesis of other two dimensional nitrides and oxides. The overall goal of the project is the development of graphene encapsulated growth as a general platform for the synthesis of novel two dimensional materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.