InSb(111)衬底上外延生长二维拓扑绝缘体锡烯/铋烯的差异性研究

Comparative study on epitaxial growth of stanene and bismuthene on InSb(111)substrate

近些年,人们对拓扑材料体系的认知得到了飞速发展.随着量子信息科学与技术成为当下科学研究的热点,具有大能隙高稳定性的低维拓扑材料有从基础研究向应用探索的趋势发展.如何实现高质量、大面积的单晶生长是影响拓扑材料走向实用化的重要一步.本文报道了在具有Sb原子终止面的InSb(111)衬底上利用分子束外延技术生长低维拓扑绝缘体锡烯与铋烯的实验结果.实验中发现,无论是锡烯还是铋烯,起始外延阶段都会在衬底上形成单层的浸润层.由于锡原子之间的相互作用远强于其与衬底的表面结合力,因此浸润层呈岛状生长,晶畴岛与岛合并的过程中边界效应明显,导致薄膜实际上由大量小晶畴拼接而成,畴壁处的缺陷难以避免.而浸润层的晶体学质量又限制了后续锡烯薄膜的外延行为,因此实验发现难以实现高质量且层数准确可控的单晶锡烯薄膜生长.而铋原子与衬底表面的结合能强于原子之间的相互作用,能够在较高温度下实现浸润层的单层层状生长,高质量的浸润层为后续铋烯的生长提供了良好的外延过渡层,因此发现实验中更容易得到大面积的铋烯薄膜.本文实验结果及相关理解对于利用半导体衬底生长低维拓扑晶体薄膜具有指导意义.

Two-dimensional topological insulator(2DTI)with a large bandgap is prerequisite for potentially observing quantum spin Hall and other quantum phenomena at room-temperature.At present,the synthesis of such materials possesses formidable challenge.In this work,we report our experimental results on synthesis of largegap 2DTI stanene and bismuthene on B-faced InSb(111)substrate by using molecular beam epitaxy technology.We find that both the stanene and bismuthene can be synthesized by following the forming of a wetting layer on InSb(111)substrate,but with different prospects.On the one hand,it is found that the binding energy between Sn and the substrate is not strong enough to compete the binding force between Sn atoms during the post annealing,thus resulting in a wetting layer composed of many small domains.It significantly restricts the quality of the stanene epilayers.On the other hand,the Bi atoms on InSb(111)are found more stable than the Sn atoms on InSb(111),resulting in a uniform wetting layer which can be optimized by adjusting substrate temperature and post-annealing conditions.Large size and single crystal bismuthene domains have been observed under the STM measurement,which also indicates a bulk gap of~0.15 eV and metallic edge states.