title: Work function of vanadium dioxide thin films across the metal-insulator transition and the role of surface nonstoichiometry.
abstract: Vanadium dioxide (VO(2)) undergoes a sharp metal-insulator transition (MIT) in the vicinity of room temperature and there is great interest in exploiting this effect in novel electronic and photonic devices. We have measured the work function of vanadium dioxide thin films across the phase transition using variable temperature Kelvin force microscopy (KFM). The work function is estimated to be ∼5.15 eV in the insulating phase and increases by ∼0.15 eV across the MIT. We further show that the work function change upon the phase transition is highly sensitive to near-surface stoichiometry studied by X-ray photoelectron spectroscopy. This change in work function is distinct from bulk resistance-versus temperature trends commonly used to evaluate synthesis protocols for such vanadium oxide films and optimize stoichiometry. The results are pertinent to understanding fundamental electronic properties of vanadium oxide as well as charge injection phenomena in solid-state devices incorporating complex oxides containing multivalence cations.
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States. cko@fas.harvard.edu
authors.forename: Changhyun
authors.initials: C
authors.lastname: Ko
authors.forename: Zheng
authors.initials: Z
authors.lastname: Yang
authors.forename: Shriram
authors.initials: S
authors.lastname: Ramanathan
mesh_terms: D008670:Metals / Q000737:chemistry; D018625:Microscopy, Atomic Force; D010087:Oxides / Q000737:chemistry*; D044367:Phase Transition; D056951:Photoelectron Spectroscopy; D013499:Surface Properties; D013696:Temperature; D017968:Vanadium Compounds / Q000737:chemistry*
chemical_list: D008670:Metals; D010087:Oxides; D017968:Vanadium Compounds