Modification of the Properties of Vanadium Oxide Thin Films by Plasma-Immersion Ion Implantation

Abstract

The paper describes the effect of doping with hydrogen and tungsten by means of plasma-immersion ion implantation (PIII) on the properties of vanadium dioxide and hydrated vanadium pentoxide films. It is shown that the parameters of the metal-insulator phase transition in VO 2 thin films depend on the hydrogen implantation dose. Next, we explore the effect of PIII on composition, optical properties, and the internal electrochromic effect (IECE) in V 2 O 5 ⋅nH 2 O films. The variations in the composition and structure caused by the hydrogen insertion, as well as those caused by the electrochromic effect, are studied by nuclear magnetic resonance, thermogravimetry, Raman spectroscopy, and X-ray structural analysis. It is shown that the ion implantation-induced hydrogenation can substantially enhance the manifestation and performance of the IECE in V 2 O 5 xerogel films. Finally, the effect of PIII-assisted doping with W on the parameters of electrical switching in Au/V 2 O 5 ⋅nH 2 O/Au sandwich structures is examined. It is shown that implanting small tungsten doses improves the switching parameters after forming. When implanting large doses, switching is observed without electroforming, and if electroforming is applied, the switching effect, on the contrary, disappears.

Metal Insulator Transition in Vanadium Dioxide Hydrated by Means of the Plasma-Immersion Ion Implantation Method

“…The implantation of hydrogen into the VO 2 films was carried out in the PIII setup described in [12] under the following conditions the discharge current was 9.5 A, discharge voltage -65.9 V, cathode heating current -65 A, pressure -4 Pa, and the gas flow was 0.0018…”

“…One of the effective ways to change the transition parameters and study its physical mechanism is doping with various elements, including hydrogen [3][4][5][6][7][8][9][10]. Previously we have reported [11,12] on the change in the properties of vanadium dioxide films and in the MIT parameters at hydrogenation by the method of plasma-immersion ion implantation (PIII). It has been found that the introduction of hydrogen by the PIII method into vanadium dioxide films with a relatively low hydrogen concentration (less than 10 at.%) leads to a decrease in the conductivity jump, i.e.…”

“…As a result of the implantation of hydrogen ions, which play the role of electron donor centers, it is possible to create a metastable VO 2 phase with metallic conductivity at a temperature below the temperature of the equilibrium phase transition for the undoped material. In addition, by varying the implantation dose, one can change the conduction jump and the phase transition temperature, which is important for practical applications [11,12].…”

“…The method of hydration proposed in this work for VO 2 using PIII [11][12][13] is fundamentally new as compared to the above. The PIII method [14], first used in the present work (and in our previous works [11][12][13]) for doping vanadium oxide thin films, possesses a number of advantages. At the PIII treatment, the sample is placed directly into the low-temperature plasma, and the implantation is carried out immediately over the entire surface of the sample.…”

“…This leads to a uniform implantation over a large area with a rapid gaining the necessary dose (and, hence, the dopant concentration), while the treatment process is low-temperature. The doping homogeneity depends only on the plasma uniformity above the sample surface, and the energy of the implanted ions can be varied from unities to hundreds of keV [12].…”