  Two-dimensional (2D) materials have received a lot of interest over the past
decade. Especially van der Waals (vdW) 2D materials, such as transition metal
dichalcogenides (TMDCs), and their heterostructures exhibit semiconducting
properties that make them highly suitable for novel device applications.
Controllable mixing and matching of the 2D materials with different properties
and a precise control of the in-plane twist angle in these heterostructures are
essential to achieve superior properties and need to be established through
large-scale device fabrication. To gain fundamental insight into the control of
these twist angles, 2D heterostructures of tungsten disulfide (WS2) and
graphene grown by bottom-up synthesis via metal-organic chemical vapor
deposition (MOCVD) are investigated using a scanning transmission electron
microscope (STEM). Specifically, the combination of conventional
high-resolution imaging with scanning nano beam diffraction (SNBD) using
advanced 4D STEM techniques is used to analyze moir\'e structures. The latter
technique is used to reveal the epitaxial alignment within the WS2/Gr
heterostructure, showing a direct influence of the underlying graphene layers
on the moir\'e formation in the subsequent WS2 layers. In particular, the
importance of grain boundaries within the underlying WS2 and Gr layers for the
formation of moir\'e patterns with rotation angles below 2{\deg} is discussed.
