基于石墨烯衬底van der Waals薄膜气-液-固外延生长的高质量氧化锌制备

Due to the lattice mismatch and difference of coefficient of thermal expansion between epilayer and substrate, the epitaxial films suffered from strains, resulting in the formation of high concentration of defects, which greatly hindered the development of semiconductor doping and the improvement of devices performance. In this research project, van der Waals epitaxy was proposed to grow high-quality defect-free ZnO films. It was found that only a weak van der Waals interaction exists at the ZnO/substrate interface that cannot cause the mismatch-induced strain in the van der Waals epitaxy, which helped lower the formation of dislocations and point defects in the ZnO epilayers. Owing to its superior properties, graphene was used as substrate in the experimental. Before growth, zinc and polycrystalline layers were pre-deposited in sequence to prevent graphene layer being destroyed by oxygen and to facilitate two dimensional growth. This research project will explore the mechanism of the initial nucleation and the film formation, and the growth kinetics with the assistance of first principle calculations. Our goal is to obtain high-quality strain-free ZnO epilayers with ultralow concentration of dislocations and point defects. With these solid cornerstones, stable and reproducible p-type ZnO materials, and furthermore, development of flexible graphene-based semiconductor microelectronic and optoelectronic devices, will have more chance.

常规外延生长模式中由于晶格失配和热失配作用，导致外延薄膜出现应变并因此形成大量缺陷，严重制约半导体掺杂技术和光电器件性能的提升。本项目提出采用新型van der Waals外延生长模式（范式生长）制备高质量ZnO薄膜。范式生长中ZnO与衬底界面处只存在范德瓦耳斯力作用，这种弱作用力不会造成薄膜内出现由失配引起的应变，有效减少缺陷的形成。我们选择石墨烯作为衬底材料，采用薄膜气-液-固生长方法克服石墨烯材料在氧气气氛下易被破坏难题，并通过预沉积覆盖层保证ZnO以二维薄膜形态生长。本项目将结合第一性原理计算，探索ZnO薄膜材料在石墨烯表面的成核机理和成膜机制，弄清ZnO薄膜生长的动力学过程，并在此基础上优化生长工艺参数，制备出高质量无应变、低缺陷密度的ZnO单晶薄膜。研究结果将为解决p型ZnO材料难题、提升光电器件工作性能提供前提条件，同时为发展石墨烯基柔性微电子、光电子器件技术打下坚实的基础。

常规外延生长模式中由于晶格失配和热失配作用，导致外延薄膜出现应变并因此形成大量缺陷，严重制约半导体掺杂技术和光电器件性能的提升。本项目提出采用新型van der Waals外延生长模式，利用石墨烯材独特的表面性质，避免和消除外延生长这ZnO/石墨烯界面的热应力，制备高质量ZnO薄膜。本项目研究内容包括探索ZnO薄膜材料在石墨烯表面的成核机理和成膜机制，弄清ZnO薄膜生长的动力学过程，在此基础上优化生长工艺参数，制备出高质量无应变、低缺陷密度的ZnO材料。研究发现，在石墨烯表面形成较强的C-O键及O在石墨烯表面可以进行无势垒的迁移，是ZnO成核的基础。同时，研究还发现在石墨烯表面形成的C-O-Zn结构可以转换为热力学更加稳定的graphene/ZnO结构，是形成范德瓦尔斯外延生长获得高质量ZnO的前提。利用CVD方法，获得了高质量的ZnO微米线阵列。本项目研究成果为发展高质量半导体薄膜材料的外延生长提供借鉴，为发展石墨烯基微电子、柔性光电子器件技术打下坚实的基础。在本项目的资助下，项目负责人及成员还开展了钙钛矿材料微纳激光器件、氮掺杂石墨烯材料等制备及应用等方面的研究工作。在本项目的资助下，发表SCI学术论文6篇。