Abstract
Scanning tunneling microscopy (STM) at 5 K is used to study WSe2 layers grown on epitaxial graphene which is formed on Si-terminated SiC(0 0 0 1). Specifically, a partial hydrogenation process is applied to intercalate hydrogen at the SiC–graphene interface, yielding areas of quasi-free-standing bilayer graphene coexisting with bare monolayer graphene. We find that an abrupt and structurally perfect homojunction (band-edge offset ~0.25 eV) is formed when WSe2 overgrows a lateral junction between adjacent monolayer and quasi-free-standing bilayer areas in the graphene. The band structure modulation in the WSe2 overlayer arises from the varying work function (electrostatic potential) of the graphene beneath. Scanning tunneling spectroscopy measurements reveal that this effect can be also utilized to create WSe2 quantum dots that confine either valence or conduction band states, in agreement with first-principles band structure calculations.
Highlights
Two-dimensional (2D) transition metal dichal cogenides (TMDs) [1] are atomically thin semiconductors that have great potential for future electronic and optoelectronic devices [2, 3]
In this Letter, we demonstrate an alternative path for creating lateral TMD homojunctions by utilizing patterned hydrogenation of the epitaxial graphene (EG) that the WSe2 layer resides on
It is shown that this approach enables one to create WSe2 quantum dots that confine either valence band (VB) or conduction band (CB) states, paving the way for tailoring TMD-based quantum materials
Summary
Yi Pan1,2,7 , Stefan Fölsch1,7 ,Yu-Chuan Lin , Bhakti Jariwala , Joshua A Robinson3 ,Yifan Nie , Kyeongjae Cho and Randall M Feenstra.
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