Evidence of a Pressure-Induced Metallization Process in Monoclinic VO2"

Raman and combined infrared transmission and reflectivity measurementswere carried out at room temperature (RT) on monoclinic VO2 over the 0 ¬19GPa and 0 ¬14 GPa pressure ranges. Both lattice dynamics and optical gapshow a remarkable stability up to P*~ 10 GPa whereas subtle modificationsof V ion arrangements within the monoclinic lattice, together with theonset of a metallization process via band gap filling, are observed for P> P*. Differently from P = 0, where the VO2 metallic phase is found onlyin conjunction with the rutile structure above 340 K, a new RT metallicphase within a monoclinic structure appears accessible in the highpressure regime