Han Delong, Tang Wenlei, Sun Naizhang, Ye Han, Chai Hongyu, Wang Mingchao
Shandong Computer Science Center (National Supercomputer Center in Jinan), Qilu University of Technology (Shandong Academy of Sciences), Jinan 250014, China.
State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876, China.
Nanomaterials (Basel). 2023 May 25;13(11):1732. doi: 10.3390/nano13111732.
A core-shell nanowire heterostructure is an important building block for nanowire-based optoelectronic devices. In this paper, the shape and composition evolution induced by adatom diffusion is investigated by constructing a growth model for alloy core-shell nanowire heterostructures, taking diffusion, adsorption, desorption and incorporation of adatoms into consideration. With moving boundaries accounting for sidewall growth, the transient diffusion equations are numerically solved by the finite element method. The adatom diffusions introduce the position-dependent and time-dependent adatom concentrations of components A and B. The newly grown alloy nanowire shell depends on the incorporation rates, resulting in both shape and composition evolution during growth. The results show that the morphology of nanowire shell strongly depends on the flux impingement angle. With the increase in this impingement angle, the position of the largest shell thickness on sidewall moves down to the bottom of nanowire and meanwhile, the contact angle between shell and substrate increases to an obtuse angle. Coupled with the shell shapes, the composition profiles are shown as non-uniform along both the nanowire and the shell growth directions, which can be attributed to the adatom diffusion of components A and B. The impacts of parameters on the shape and composition evolution are systematically investigated, including diffusion length, adatom lifetime and corresponding ratios between components. This kinetic model is expected to interpret the contribution of adatom diffusion in growing alloy group-IV and group III-V core-shell nanowire heterostructures.
核壳纳米线异质结构是基于纳米线的光电器件的重要构建单元。本文通过构建合金核壳纳米线异质结构的生长模型，考虑吸附原子的扩散、吸附、脱附和掺入，研究了吸附原子扩散引起的形状和成分演变。通过移动边界考虑侧壁生长，用有限元方法对瞬态扩散方程进行了数值求解。吸附原子的扩散引入了组分A和B的位置和时间相关的吸附原子浓度。新生长的合金纳米线壳层取决于掺入率，导致生长过程中形状和成分的演变。结果表明，纳米线壳层的形态强烈依赖于通量入射角。随着该入射角的增加，侧壁上最大壳层厚度的位置向下移动到纳米线底部，同时，壳层与衬底之间的接触角增大到钝角。结合壳层形状，成分分布在纳米线和壳层生长方向上均表现为不均匀，这可归因于组分A和B的吸附原子扩散。系统研究了参数对形状和成分演变的影响，包括扩散长度、吸附原子寿命和组分之间的相应比例。该动力学模型有望解释吸附原子扩散在生长合金IV族和III-V族核壳纳米线异质结构中的作用。
