The Control of Transition Behavior of VO2 Film Deposited on Sapphire (0001) Substrate by the Organic Polymer‐Assisted Thermal Deposition

We present the effects of organic additives (sucrose, polyvinylalcohol [PVA], and polyvinylpyrrolidone [PVP]) on a precursor solution (VO2+ ion) to the physicochemical properties of the thermally deposited VO2 film on sapphire (0001) plane. All the VO2 films, which deposited with assistance of the organic chemicals, showed a sudden change in resistance measurement near 340 K, but the sudden change did not appear in the film which deposited without the organic additives. The X‐ray diffractometer patterns of the films show monoclinic type VO2 (M‐VO2) as main phase, which has preferred growing axis (020) and (−211), and V2O5 as impurity phase. The intensity of the impurity peaks was minimized in PVP‐assisted deposition and showed the best performance as a smart window, ~10% transmittance gap between low and high temperature phases at 1550 nm. The atomic ratio of oxygen/carbon in the organic additives (1:1 in sucrose –[CH2O]n–, 1:2 in PVA –[C2H4O]n–, and 1:6 in PVP –[C6H9NO]n–) seems an important condition to determine the performance of the smart window.