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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.
During droplet epitaxial growth, metal droplets bear the role of growth precursors and directly determine the density, size, position and other parameters of subsequent quantum rings, quantum dots and nanowires.In this paper, epitaxy, the frontal research on Ga-droplet is controlled by in-situ laser effect.At first, MBE was used to deposit 6 ML Ga atoms on GaAs (001) substrate to obtain a Ga-droplet density of 5.7 × 10 ~ (10) cm ~ (-2) surface, and then the single-pulse laser was introduced into the surface of the substrate in situ.The results show that under the laser irradiation (energy density greater than 10 m J / cm ~ 2), a significant and abundant migration was started to overcome the migration barrier in all directions, and the intensity of this migration had a strong positive correlation with the laser energy.With this migration, different Ga-droplets , The density and the size of the Ga-droplet will be strongly affected by the random fusion.The statistics show that when the laser energy is increased from 10 m J / cm 2 to 30 m J / cm 2, the density of the Ga-droplet will decrease rapidly To nearly one-third of the original, while the size is rapidly increasing , And the overall distribution from the traditional “narrow band ” to “broadband ” characteristics of the transition.Thus through the study of this paper, it is confirmed and found that there is extremely sensitive to the droplet surface "photo-migration A feature that can not only achieve the second modification of the overall size and density of the droplet, but also obtain some distribution features that are difficult to be achieved by the conventional droplet epitaxy. In the future, we will be fully expected to realize the droplet control by means of multi-beam interference. Artificially controlled droplet epitaxy technology, thereby greatly promoting the growth of the entire low-dimensional nano-semiconductor materials.