潘毅  (教授)

2D Materials: WSe2 homojunctions and quantum dots

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发布时间：2019-01-18

发布时间：2019-01-18

文章标题：2D Materials: WSe2 homojunctions and quantum dots

内容：

Our  paper:

WSe₂ homojunctions and quantum dots created by patterned hydrogenation of epitaxial graphene substrates

has been published on 2D Materials.

http://iopscience.iop.org/article/10.1088/2053-1583/aaf58c/meta

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.

The abrupt lateral p-n junction:

The mechanism:

 Y.P., S.F, and R.M.F. carried out the STM experiments, and they wrote the paper with inputs from other authors. Y.N. performed the first-principles computations under the supervision of K.C.  Y.C.L. and  B.J.prepared the samples, under the supervision of J.A.R.