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Tyson C. Back

Publications and source records attributed to Tyson C. Back.

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Real-time Observation of Thermal Surface Recovery in $SrVO_3$

$SrVO_3$ (SVO), a model correlated metal and a promising transparent conducting oxide, develops a several-nanometer-thick near-surface region (NSR), rich in $V^{5+}$ species under ambient conditions. This oxidized layer obscures the intrinsic correlated-metallic $V^{4+}$ character and limits both fundamental studies of the physics and the material's integration into electronic devices. Here, we demonstrate a direct and controllable approach for recovering the metallic SVO surface by thermally reducing the NSR under ultra-high vacuum. Real-time in-situ X-ray photoelectron spectroscopy (XPS) reveals a sharp transformation from a $V^{5+}$-dominated surface to mixed valence states, dominated by $V^{4+}$, and a recovery of its metallic character. Ex-situ X-ray diffraction (XRD), atomic force microscopy (AFM), and high-resolution scanning electron microscopy (HR-SEM) suggest that this transformation is accompanied by mass redistribution and partial oxygen loss, leading to nanoscale surface reorganization and modest lattice expansion. While thermodynamic considerations motivate evaluation of a $V_2O_5$ volatilization pathway, the combined experimental evidence instead points toward a predominantly structural surface reorganization. These findings establish a practical method for obtaining predominantly $V^{4+}$ SVO surfaces without protective capping layers, a capability that expands the utility of SVO for advanced spectroscopies, interface engineering, and oxide-electronics device integration.

cond-mat.mtrl-sci

Work Function Characterization of the Directionally Solidified LaB6 VB2 Eutectic

With its low work function and high mechanical strength, the LaB6/VB2 eutectic system is an interesting candidate for high performance thermionic emitters. For the development of device applications, it is important to understand the origin, value, and spatial distribution of the work function in this system. Here we combine thermal emission electron microscopy and low energy electron microscopy with Auger electron spectroscopy and physical vapour deposition of the constituent elements to explore physical and chemical conditions governing the work function of these surfaces. Our results include the observation that work function is lower (and emission intensity is higher) on VB2 inclusions than on the LaB6 matrix. We also observe that the deposition of atomic monolayer doses of vanadium results in surprisingly significant lowering of the work function with values as low as 1.1 eV.

cond-mat.mtrl-sci