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  1. Abstract

    The presence of inclusions, twinning, and low-angle grain boundaries, demanded to exist by the third law of thermodynamics, drive the behavior of quantum materials. Identification and quantification of these structural complexities often requires destructive techniques. X-ray micro-computed tomography (µCT) uses high-energy X-rays to non-destructively generate 3D representations of a material with micron/nanometer precision, taking advantage of various contrast mechanisms to enable the quantification of the types and number of inhomogeneities. We present case studies of µCT informing materials design of electronic and quantum materials, and the benefits to characterizing inclusions, twinning, and low-angle grain boundaries as well as optimizing crystal growth processes. We discuss recent improvements in µCT instrumentation that enable elemental analysis and orientation to be obtained on crystalline samples. The benefits of µCT as a non-destructive tool to analyze bulk samples should encourage the community to adapt this technology into everyday use for quantum materials discovery.

  2. ScSI, a missing member of the rare earth sulfoiodide (RESI) family of materials, has been synthesized for the first time. ScSI crystallizes in the FeOCl structure type, space group Pmmn (No. 59), a = 3.8904(2), b = 5.0732(9), c = 8.9574(6) Å. Both hyperspectral reflectance measurements and ab initio calculations support the presence of an indirect optical band gap of 2.0 eV. The bulk crystal is found to be readily exfoliatable, enabling its use as an optical component in novel heterostructures. The impact of lithium intercalation on its electronic band structure is also explored. A broader correlation is drawn between the observed structural trends in all known 1:1:1 sulfoiodide phases, cationic proportions, and electronic considerations. The realization of this phase both fills a significant synthetic gap in the literature and presents a novel exfoliatable phase for use as an optical component in next-generation heterostructure devices.
    Free, publicly-accessible full text available July 1, 2023
  3. Free, publicly-accessible full text available August 17, 2023
  4. Rutile compounds have exotic functional properties that can be applied for various electronic applications; however, the limited availability of epitaxial substrates has restricted the study of rutile thin films to a limited range of lattice parameters. Here, rutile GeO 2 is demonstrated as a new rutile substrate with lattice parameters of [Formula: see text] and [Formula: see text]. Rutile GeO 2 single crystals up to 4 mm in size are grown by the flux method. X-ray diffraction reveals high crystallinity with a rocking curve having a full width half-maximum of 0.0572°. After mechanical polishing, a surface roughness of less than 0.1 nm was obtained, and reflection high-energy electron diffraction shows a crystalline surface. Finally, epitaxial growth of (110)-oriented TiO 2 thin films on GeO 2 substrates was demonstrated using molecular beam epitaxy. Templated by rutile GeO 2 substrates, our findings open the possibility of stabilizing new rutile thin films and strain states for the tuning of physical properties.
    Free, publicly-accessible full text available September 1, 2023