Abstract
During growth of two-dimensional (2D) materials, abrupt growth of multilayers is practically unavoidable even in the case of well-controlled growth. In epitaxial growth of a quintuple-layered {{rm{Bi}}}_{2}{{rm{Se}}}_{3} film, we observe that the multilayer growth pattern deduced from in situ x-ray diffraction implies nontrivial interlayer diffusion process. Here we find that an intriguing diffusion process occurs at step edges where a slowly downward-diffusing Se adatom having a high step-edge barrier interacts with a Bi adatom pre-existing at step edges. The Se–Bi interaction lowers the high step-edge barrier of Se adatoms. This drastic reduction of the overall step-edge barrier and hence increased interlayer diffusion modifies the overall growth significantly. Thus, a step-edge barrier reduction mechanism assisted by hetero adatom–adatom interaction could be fairly general in multilayer growth of 2D heteroatomic materials.
Highlights
Two-dimensional (2D) layered materials generally have weak van der Waals interactions between layers.[1,2,3,4] These systems possess strong anisotropic properties that are exploited to tailor optoelectronic, spintronic, and thermoelectric devices to meet practical requirements.[5,6] Sizable growth of 2D atomic layers in high quality is required for application and it will be enabled by optimizing the growth kinetic parameters
The overall patterns of simple epitaxial growth have been explained with growth parameters such as interlayer diffusion, terrace diffusion, and 2D
The transition energy barrier of the Bi adatom from the metastable to the most stable configuration is as small as 0.10 eV from the nudged elastic band (NEB) method calculation.[25]
Summary
Two-dimensional (2D) layered materials generally have weak van der Waals (vdW) interactions between layers.[1,2,3,4] These systems possess strong anisotropic properties that are exploited to tailor optoelectronic, spintronic, and thermoelectric devices to meet practical requirements.[5,6] Sizable growth of 2D atomic layers in high quality is required for application and it will be enabled by optimizing the growth kinetic parameters. The overall patterns of simple epitaxial growth have been explained with growth parameters such as interlayer diffusion, terrace diffusion, and 2D nucleation within the framework of the standard kinetic multilayer growth model.[7,8,9] During complex layered-material growth, density of mobile atoms is enhanced on the dimensionally reduced surface, especially near steps that occur at the lateralgrowth-front of islands on surface. In this situation, a simple hopping model of free adatoms may fail to describe the interlayer diffusion process. As a model system of the vdW epitaxial growth, we study
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