initio-based scanning Seebeck microscopy simulation of epitaxial graphene on 6H-SiC

Heat, diffusive and incoherent phenomena, has not been considered as surface scanning means. In spite of those characteristics of heat, the local variation of charge carrier was shown by using coherent electron transport via the temperature difference between tip and sample which is so-called scanning thermoelectric microscopy (SThM). It successfully measured atomic-scale local majority carriers variation at room temperature.

We conducted first-principle scanning Seebeck microscopy (SSM) simulation in order to explain heat-based SThM images. The SSM simulation of freestanding monolayer graphene could successively reproduce the experimental thermoelectric contrast between carbon and void sites at the atomic scale. More importantly, SThM for the supported graphene showed the unique oblique slope of the thermoelectric voltage between A and B sites in graphene unit cell stem from the difference of local charge carrier environment.

Here, SSM simulations for free-standing bilayer graphene and supported monolayer graphene on 6H-SiC are numerically demonstrated. The Seebeck profile of both cases was able to show the opposite results of A and B sites depending on the Fermi energy, and the oblique slope of the previous study could not be explained.