分子束外延原位脉冲激光驱动金属Ga-droplet迁移的实现和研究  

Demonstration and study of Ga-droplet migrating propelled by in-situ laser based on MBE

作　　者：霍大云 石震武 徐超[1] 邓长威 陈晨[1] 张伟[1] 陈林森[1] 彭长四[1] HUO DaYun SHI ZhenWu XU Chao DENG ChangWei CHEN Chen ZHANG Wei CHEN LinSeng PENG ChangSi(School of Optoelectronics Information Science and Engineering, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China)

机构地区：[1]苏州大学光电信息科学与工程学院苏州纳米科技协同创新中心,苏州215006

出　　处：《科学通报》2017年第28期3379-3384,共6页Chinese Science Bulletin

基　　金：国家自然科学基金(11504251;51302179);江苏高校优势学科建设工程项目;科技部国际合作项目(2013DFG12210);江苏省高校自然科学研究重大项目(12KJA140001);江苏省普通高校研究生科研创新计划(KYLX15_1252)资助

摘　　要：在液滴外延生长过程中金属液滴承担着生长前驱体的角色,直接决定着后续量子环、量子点、纳米线等量子结构的密度、尺寸、位置等参数.本文开展了在MBE(molecular beam epitaxy)液滴外延过程中通过原位激光作用调控金属Ga-droplet的前沿研究.首先利用MBE在GaAs(001)衬底上(150℃)沉积6 ML Ga原子以获得Ga-droplet密度约为5.7×10^(10) cm^(-2)的表面,然后原位引入单脉冲单束激光辐照衬底表面.实验观察到:Ga-droplet在激光辐照(能量密度大于10 m J/cm^2)的条件下将开始克服表面各个方向的迁移势垒发生显著而丰富的迁移行为,且这种迁移的剧烈程度与激光能量具有强烈的正相关规律.伴随这种迁移,不同Ga-droplet之间将发生随机的融合,从而强烈影响其密度以及尺寸.统计表明:当激光能量从10 m J/cm^2提高至30 m J/cm^2时,Ga-droplet的密度将迅速减小到近原来的三分之一,同时尺寸则迅速地增大,且整体分布由传统的"窄带"向"宽带"特点过渡.故通过本文的研究,证实和发现了液滴存在着极为敏感的表面"光致迁移"特性.凭借这一特性,不仅可实现对液滴整体尺寸、密度的二次修饰,获得一些在传统液滴外延中难以实现的分布特点,而且在将来我们完全有望凭借多光束干涉图形化调控液滴,最终实现人为可控的液滴外延技术,从而极大地推动整个低维纳米半导体材料的生长.In droplet epitaxy, as is well known that the metallic droplets would closely determine the density, size and site of the following quantum structures such as quantum dot/ring, nano wire and son on because they usually act as the precursors. Recently, to search for the method of effectively manipulating the droplets shows great significance. In this paper, we have conducted a pioneering study of in-situ laser manipulating droplets in the droplet epitaxy basing MBE. A layer of Ga-droplets （density： 5.7×10^10 cm^-2） on GaAs （001） was first prepared by MBE deposition of 6ML Ga at the temperature of 150℃ with a growth rate of 0.18 ML/s and an interrupt of as flux. Then a single pulse of mono-beamed laser （355 nm/10 ns） was in-situ introduced to shoot on it and the morphology evolution was carefully studied by AFM and the mechanism was also discussed simply. It is observed： As （laser） energy density reached above 10 mJ cm-2, the Ga droplet was able to escape from the surface potential trap in all-direction and began to migrate randomly and even in a very small area of several hundred nanometers various migrations （along different surface orientations） could been seen. This was explained as： since the Ga droplets are disorderly locating on the GaAs surface, even for two closest neighbor droplets within a typical distance of hundred nanometers, the surrounding situations for them might be distinctly non-equivalent in the terms of the droplet size （height/diameter）, density and the inter-droplet relative position. So when the laser pulse heated the surface, such disorder will cause a chaotic fluctuation in surface local thermal field. Then as a consequence, the droplets will move around with the diffusion force under the gradient of temperature. Accompanying with the migration, coalescence （among different droplets） might take places during the collision which could remarkably modify the Ga-droplet morphology. And this kind of modifying strongly depended on laser energy density. Stati

关 键 词：Ga—droplet 分子束外延 原位激光 光致迁移 

分 类 号：TN304[电子电信—物理电子学]