V. A. Mikhalevsky

Influence of the conditions of pulsed laser deposition on the structural, electrical, and optical properties of VO2 thin films

The technique of pulse laser deposition with the separation of plume drops is used to produce VO2 thin films on sapphire(0001) and silicon(111) substrates. It is established that the energy density at the target and the oxygen pressure influence the structural and electrical properties of the films. All of the VO2 crystal films exhibit semiconductor-metal transitions with a substantial change in the resistance (by 2–5 orders of magnitude). The transmittance in the range 200–800 nm and reflectance in the range 400–700 nm are studied in the temperature range from 20 to 100°C. The transmittance of the films at wavelengths from 300 to 800 nm shows a jump and hysteresis upon heating and cooling. It is for the first time established that the changes in the transmittance of the film are different in character at different wavelengths and the shape of the temperature hysteresis loop for optical transmittance in the visible and near-ultraviolet regions does not in all areas replicate the shape of the hysteresis loop for the resistivity of the VO2 films. The difference in the behavior of the hysteresis curves for the transmittance and resistance is attributed to variations in the absorption of the films under variations in temperature.

Luminescence Properties of Cd x Zn 1 – x O Thin Films

Thin CdxZn1 – xO films with a Cd content in the range from zero to 35 at % are synthesized by pulsed laser deposition. A record-breaking solubility limit of 30 at % of Cd in wurtzite-structured CdxZn1 – xO thin films is attained. Apart from the exciton peak, additional peaks associated with an inhomogeneous distribution of Cd in the samples are observed in the low-temperature (10 K) photoluminescence spectra of Cd0.15Zn0.85O and Cd0.3Zn0.7O films. An unsteady (S-like) temperature dependence of the spectral position of the exciton photoluminescence peak in CdxZn1 – xO films is observed. Such a dependence is associated with the effect of the localization of charge carriers.

Influence of Oxygen Vacancies on the Magnetic Properties of Zn 1 – x Co x O y Films

Thin films of Zn1 – xCoxOy (х = 0–0.3) with a temperature of the ferromagnetic transition of ТС > 300 K are obtained from ZnO–Co3O4 ceramic targets. The electron concentration in the films is found to decrease exponentially with increasing cobalt content. It is revealed that the magnetization of the films obtained under oxygen deficiency conditions varies in a nonmonotonous way as the cobalt concentration increases. This is caused by the oxidation of metallic nanoclusters of cobalt due to an increase in the oxygen content in the targets. Investigation of the transmission spectra of Zn1 – xCoxOy films revealed extrema in the visible region of the spectrum and near the edge of the fundamental absorption band, associated with electron states introduced by cobalt.

Vanadium- and Titanium Dioxide-Based Memristors Fabricated via Pulsed Laser Deposition

Thin TiOx and VO2 – x films are fabricated via pulsed laser deposition from metal targets with the help of mask technologies. Their memristive properties are investigated using Au/TiOx1/TiOx2/Au and Au/VO2/VO2 – x/Au thin-film structures, and the possible mechanisms of resistive switching are discussed. The structures are obtained at room temperature in an oxygen atmosphere.