Vacancy-induced electronic states in substoichiometric V2 −x Mo x O3 ±y thin films and powders—A soft X-ray emission study

Abstract

Vanadium oxide as well as molybdenum oxide thin films have been found to show electrochromism and metal insulator transitions. Incorporation of vanadium ion into molybdenum oxide lattice not only changes the lattice parameters but also shows prominent spectral changes in X-ray emission spectra. K~l-3 emission spectra of vanadium in different alloy films of V2Os-MoO3 system have been studied here and these have been compared with the X-ray emission spectra of similar composition of V2Os-MoO3 powders. For K~_3 emission, the difference in values of asymmetry indices of thin films and powders is marginal, although considerable tailing towards high energy is observed in thin films. By curve fitting procedure, the K/~_3 emission spectra have been resolved to several gaussian peaks, and these have been explained on the basis of vacancy-induced electronic states, crossover transitions advocated in molecular orbital theory and plasmon oscillation.

Molybdenum x‐ray emission spectroscopic study of vacancy‐induced electronic states in V2O5–MoO3 thin films and powders

“…Various compositions of V 2 O 5 and MoO 3 composite powders and thin films deposited over borosilicate glass plates were prepared according to the procedure reported previously. 13 The samples were characterized by x-ray diffraction before being subjected to an x-ray emission study. X-ray emission spectra of the samples were recorded with a Philips PW-1400 wavelength-dispersive spectrometer system having a scandium x-ray tube operating at 50 kV and 60 mA.…”

“…5 -7 Studies on the density of states and electronic properties of Mo and Nb have been carried out by Papaconstantopoulos et al 8,9 Although x-ray photoelectron spectroscopy work on oxides of vanadium and molybdenum has been reported, 10 -12 studies on powders and thin films of varying V 2 O 5 -MoO 3 compositions have only recently been reported. 13 Like many transition metal oxides, V 2 O 5 and MoO 3 find extensive use in catalysts, intercalation compounds, electrochromic applications and cathodic material for lithium batteries. 14 -17 The electrochromic behaviour of V 2 O 5 and MoO 3 thin films deposited by various methods has been reported to be highly structure dependent and the metal-insulator transition in VO x is very much complicated owing to crystallographic changes taking place at transition.…”