Stoichiometry Engineering of Monoclinic to Rutile Phase Transition in Suspended Single Crystalline Vanadium Dioxide Nanobeams

Coexisting monoclinic M-1 (insulating) and rutile (metallic) domains were observed in free-standing vanadium dioxide nanobeams at room temperature. Similar domain structures have been attributed to interfacial strain, which was not present here. Annealing under reducing conditions indicated that a deficiency of oxygen stabilizes the rutile phase to temperatures as low as 103 K, which represents an unprecedented suppression of the phase trasition by 238 K. In a complementary manner, oxygen-rich growth conditions stabilize the metastable monoclinic M-2 and triclinic T (or M-3) phases. A pseudophase diagram with dimensions of temperature and stoichiometry is established that hightlights the accessibility of new phases in the nanobeam geometry.