  Vanadium diselenide (VSe2) has intriguing physical properties such as
unexpected ferromagnetism at the two-dimensional limit. However, the
experimental results for room temperature ferromagnetism are still
controversial and depend on the detailed crystal structure and stoichiometry.
Here we introduce crystal truncation rod (CTR) analysis to investigate the
atomic arrangement of bilayer VSe2 and bilayer graphene (BLG) hetero-structures
grown on a 6H-SiC(0001) substrate. Using non-destructive CTR analysis, we were
able to obtain electron density profiles and detailed crystal structure of the
VSe2/BLG heterostructures. Specifically, the out-of-plane lattice parameters of
each VSe2 layer were modulated by the interface compared to that of the bulk
VSe2 1T phase. The atomic arrangement of the VSe2/BLG heterostructure provides
deeper understanding and insight for elucidating the magnetic properties of the
van der Waals heterostructure.
