Structural and electrical properties of V₂O₃ thin films on c-plane Al₂O₃ fabricated by reactive-HiPIMS and dcMS techniques

Abstract

The study presents the synthesis of epitaxial V2O3 thin films on c-plane Al2O3 substrates by reactive high-power impulse (HiPIMS) and direct current (dcMS) magnetron sputtering. The results reveal that for fixed deposition conditions and discharge power, well defined epitaxial layers can be attained using both HiPIMS and dcMS. For dcMS we observe the formation of these epitaxial films down to flow rate values of 1.3 sccm while for HiPIMS we observe an extended operation window down to much lower oxygen flow of 0.5 sccm without sacrificing the structural quality of the films. Furthermore, the effect of varying HiPIMS discharge parameters i.e. repetition frequency and average power for fixed O2 flow setting, were explored in order to determine their effect on the structural quality and electrical characteristics of the films. The magnitude of the metal–insulator transition (MIT) and the transition temperature is correlated to the film stoichiometry which can be fine-tuned by mapping the HiPIMS discharge parameters, displaying a total change in resistance of ∼7 decades over the studied temperature range. The MIT temperature and magnitude obtained for films fabricated by HiPIMS, even for low O2 flow settings (down to 0.6–0.5 sccm), displayed superior characteristics compared to films fabricated by dcMS where a minimum O2 flow of 1.3 sccm was needed.

Reversible exchange bias in epitaxial V2O3/Ni hybrid magnetic heterostructures

“…The VSM hysteresis loops were recorded at the maximum applied field of 200 G while the MOKE magnetization loops were recorded at the maximum applied field of 400 G. [13,26]. This temperature range corresponds well to the transition temperature determined initially by electrical resistance measurements [23].…”

“…A detailed discussion of the fully strained component can be found elsewhere [16,22]. Ex situ atomic force microscopy (AFM) of the top V 2 O 3 interface was conducted by depositing a series of V 2 O 3 films, without depositing the subsequent Ni and capping Zr layers, with results presented in [23,24]. The RMS roughness of the films, determined from the AFM scans, was between 0.2-0.5 nm in agreement with values for the buried interface derived from the XRR and PNR fits described further below.…”

Reversible control of the metal-insulator transition in V2O3 thin films through plasma hydrogenation

“…The HiPIMS deposition was made at a pulse length of 100 μs and repetition frequency of 350 Hz, giving an average power of 200 W over the target area. Further details on the fabrication conditions and deposition parameters can be found in [8].…”

“…In this study we investigate the effect of incorporating hydrogen through plasma hydrogenation on the MIT characteristic of V 2 O 3 films without utilizing a metal catalyst on the surface as in studies [11,[18][19][20]. The structures are similar to structures already studied in our previous work [8] and are comprised of V 2 O 3 thin films (∼22 nm) deposited on to c-plane Al 2 O 3 .…”

“…For V 2 O 3 thin films grown on crystalline substrates, the MIT characteristics can be varied with the choice of substrate materials and surface orientations, deposition methods, discharge parameters, strain state and the doping level [7][8][9]. A continual interest has been on determining the effect of doping on the MIT characteristics of V 2 O 3 for instance utilizing titanium (Ti), tungsten(W), chromium (Cr) as well as vanadium vacancies.…”