Abstract
Vanadium oxide films amorphous, nonstoichiometric and highly absorbing in the optical region were deposited on ITO-coated glass and on silicon substrates, by the hot-filament metal oxide deposition technique (HFMOD) and oxidized by ex-situ annealing in a furnace at 200, 300, 400 and 500 oC, under an atmosphere of argon and rarefied oxygen. X-ray diffraction, Raman and Rutherford backscattering spectroscopy as well as optical transmission were employed to characterize the amorphous and annealed films. When annealed at 200 and 300 oC the as-deposited opaque films become transparent but still amorphous. Under treatments at 400 and 500 oC a crystalline nonstoichiometric V2O5 structure is formed. All the annealed films became semiconducting, with their optical absorption coefficients changing with the annealing temperature. An optical gap of 2.25 eV was measured for the films annealed at 400 and 500 oC. The annealing in rarefied oxygen atmosphere proved to be a useful and simple ex-situ method to modulate the structural and optical properties of vanadium oxide films deposited by HFMOD technique. This technique could be applied to other amorphous and non-absorbing oxide films, replacing the conventional and sometimes expensive method of modulate desirable film properties by controlling the film deposition parameters. Even more, the HFMOD technique can be an inexpensive alternative to deposit metal oxide films.
Highlights
Thin films of vanadium oxides find optical applications as an electroactive material for electrodes of electrochromic devices [1], as hole injection material in organic light-emitting diode (OLED) [2], in optical switching and optical memory devices [3], as antireflective coating [4], among others applications
In this paper we present the results of structural and optical characterizations of as-grown and posannealed thin films of vanadium oxide deposited by the hot-filament metal oxide deposition technique (HFMOD) technique on Indium tin oxide (ITO)-glass substrates
Indium tin oxide (ITO)-coated glass slides and (100) silicon slabs were used as substrates, and were placed 36 mm below the filament wire, on a water-cooled copper base
Summary
Thin films of vanadium oxides find optical applications as an electroactive material for electrodes of electrochromic devices [1], as hole injection material in organic light-emitting diode (OLED) [2], in optical switching and optical memory devices [3], as antireflective coating [4], among others applications. For these devices the vanadium oxide films are usually deposited on ITO-coated slabs, due to its optical transparency and electrical conductivity. The deposition of vanadium oxide films by the hot-filament metal oxide deposition technique (HFMOD) is scarcely reported
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