  The metal-insulator transition (MIT) observed in vanadium dioxide (VO2) has
been a topic of great research interest for past decades, with the underlying
physics yet not fully understood due to the complex electron interactions and
structures involved. The ability to understand and tune the MIT behaviour is of
vital importance from the perspective of both underlying fundamental science as
well as potential applications. In this work, we use scanning transmission
electron microscopy (STEM) to investigate cross-section lamella of the VO2
films deposited using pulsed laser deposition (PLD) on three substrates: c-cut
sapphire, TiO2(101) and TiO2(001). Advanced STEM imaging is performed in which
also the oxygen atom columns are resolved. We link the overall film quality and
structures on atomic and nanoscale to the electrical transition
characteristics. We observe poor MIT characteristics on c-sapphire due to the
presence of very small domains with six orientation variants, and on TiO2 (001)
due to the presence of cracks induced by stress relaxation. However, the MIT on
TiO2 (101) behaves favourably, despite similar stress relaxation which,
however, only lead to domain boundaries but no cracks.
