Direct Imaging and Electronic Structure Modulation of Double Moir\'e Superlattices at the 2D/3D Interface

The atomic structure at the interface between a two-dimensional (2D) and a three-dimensional (3D) material influences properties such as contact resistance, photo-response, and high-frequency performance. Moire engineering has yet to be explored for tailoring this 2D/3D interface, despite its success in enabling correlated physics at 2D/2D twisted van der Waals interfaces. Using epitaxially aligned MoS$_2$ /Au{111} as a model system, we apply a geometric convolution technique and four-dimensional scanning transmission electron microscopy (4D STEM) to show that the 3D nature of the Au structure generates two coexisting moire periods (18 Angstroms and 32 Angstroms) at the 2D/3D interface that are otherwise hidden in conventional electron microscopy imaging. We show, via ab initio electronic structure calculations, that charge density is modulated with the longer of these moire periods, illustrating the potential for (opto-)electronic modulation via moire engineering at the 2D/3D interface.