Strong hybridization of two-magnon scattering with phonons is observed in 2D antiferromagnet MnPSe 3 .

Abstract

Vanadium dioxide (VO 2 ) has been widely studied due to its metal-insulator phase transition at 68°C, below which it is a semiconducting monoclinic phase, P2 1 /c, and above it is a metallic tetragonal phase, P4 2 /mnm. Substituting vanadium with transition metals allows transition temperature tunability. An accelerated microwave-assisted synthesis for VO 2 and 5d tungsten-substituted VO 2 presented herein decreased synthesis time by three orders of magnitude while maintaining phase purity, particle size, and transition character. Tungsten substitution amount was determined using inductively coupled plasma-optical emission spectroscopy. Differential scanning calorimetry, superconducting quantum interference device measurements, and in situ heating and cooling experiments monitored through synchrotron X-ray diffraction (XRD) confirmed the transition temperature decreased with increased tungsten substitution. Scanning electron microscopy analyzed through the line-intercept method produced an average particle size of 3-5 μm. Average structure and local structure phase purity was determined through the Rietveld analysis of synchrotron XRD and the least-squares refinement of pair distribution function data.

We present vanadium dioxide (VO2) thin films having high resistivity contrast with silicon substrates through use of crystallized alumina (Al2O3) buffer layers, engineered for this purpose. We first optimized the process by depositing VO2 onto C-plane sapphire substrates prior to alumina thin films. The latter of which were grown via atomic layer deposition on silicon substrates. We then applied rapid thermal annealing (RTA) to crystallize the alumina films. Scanning electron microscopy results indicated a thickness of 107 nm for each VO2 film, which yielded hot–cold resistivity contrast ratios of 9.76 × 104, 1.46 × 104, and 3.66 × 103, when deposited on the C-plane sapphire, the annealed buffers, and the as-deposited alumina buffers, respectively. Atomic force microscopy of the film surface roughness of the VO2 films indicated root mean squared roughness (Rq) of 4.56 nm, 6.79 nm, and 3.30 nm, respectively, for the films grown on the C-plane sapphire, annealed buffers, and as-deposited buffers. Finally, x-ray diffraction (XRD) of the VO2 films indicated the desired composition and strong (0h0)/(00h) texturing, when deposited on both the C-plane sapphire and the annealed alumina buffer layers. XRD results indicated a series of peaks corresponding to the α-Al2O3/C-plane sapphire, and an XRD analysis of the buffers alone confirmed crystallization of the buffer layer via RTA. The process defined in this paper produced a series of highly textured VO2 films making them most valuable for the integration of VO2 with silicon-based devices.

No abstract