Anisotropy, band-to-band transitions, phonon modes, and oxidation properties of cobalt-oxide core-shell slanted columnar thin films

Mock, A.; Korlacki, Rafał; Briley, Chad; Sekora, Derek; Hofmann, Tino; Wilson, Peter M.; Sinitskii, Alexander; Schubert, Eva; Schubert, Mathias

doi:10.1063/1.4941399

Cited by 13 publications

(7 citation statements)

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“…There was no significant evidence of anisotropy in the variable angle spectroscopic ellipsometry (VASE) data. Spectroscopic ellipsometry is an indirect measurement technique, which utilizes changes in polarization of light reflected off or transmitted through a sample [37,38]. An appropriate physical model is necessary to accurately describe the optical properties of the material.…”

Section: Resultsmentioning

confidence: 99%

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Electrical and material properties of hydrothermally grown single crystal (111) UO2

et al. 2018

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The semiconductor and optical properties of UO2 are investigated. The very long drift carrier lifetimes, obtained from current-voltage I(V) and capacitance-voltage C(V) measurements, along with the well-defined optical properties provide little evidence of an abundance of material defects away from the surface region. Schottky barrier formation may be possible, but very much dependent on the choice of contact and surface stoichiometry and we find that Ohmic contacts are in fact favored. Depth resolved photoemission provided evidence of a chemical shift at the surface. Density functional theory, with the Heyd-Scuseria-Ernzerhof (HSE) functional, indicates a band gap of a 2.19 eV and an anti-ferromagnetic ground state. Ellipsometry measurements indicates at UO2 is relatively isotropic with a band gap of approximately 2.0 eV band gap, consistent with theoretical expectations.

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Section: Resultsmentioning

confidence: 99%

“…with best-match parameters of amplitude, A, center energy, E n , and broadening, B r [37]. The real part, ε 1 , is obtained from Kramers-Kronig transformation such that:…”

Section: Resultsmentioning

confidence: 99%

Electrical and material properties of hydrothermally grown single crystal (111) UO2

et al. 2018

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“…Previous analysis reports from single-material SCTFs, core-shell SCTFs 41,43 and SCHTFs 44 introduced the homogeneous biaxial layer approach (HBLA) 38 . The HBLA method assumes that the linear optical response of SC(H)TFs can be described by a single homogeneous layer permitting line-shape function independent wavelength-by-wavelength determination of effective major dielectric functions along three major dielectric polarizability axes, N a , N b , and N c (Fig.…”

Section: Methodsmentioning

confidence: 99%

“…It was observed that the Au nanoparticles increased the anisotropy of the SCTFs 39,40 . Composites of multiple materials can be achieved, for example, by fabrication of core-shell SCTFs using atomic layer deposition 41 , chemical vapor deposition 42 , or post-growth oxidation 43 . Alternatively, in a rather new approach, slanted columnar heterostructure thin films (SCHTFs) can be fabricated by subsequent change of the source material during the GLAD growth (Fig.…”

Section: Introductionmentioning

confidence: 99%

Tunable plasmonic resonances in Si-Au slanted columnar heterostructure thin films

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Mock

Feder

et al. 2019

Sci Rep

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We report on fabrication of spatially-coherent columnar plasmonic nanostructure superlattice-type thin films with high porosity and strong optical anisotropy using glancing angle deposition. Subsequent and repeated depositions of silicon and gold lead to nanometer-dimension subcolumns with controlled lengths. We perform generalized spectroscopic ellipsometry measurements and finite element method computations to elucidate the strongly anisotropic optical properties of the highly-porous Si-Au slanted columnar heterostructures. The occurrence of a strongly localized plasmonic mode with displacement pattern reminiscent of a dark quadrupole mode is observed in the vicinity of the gold subcolumns. We demonstrate tuning of this quadrupole-like mode frequency within the near-infrared spectral range by varying the geometry of Si-Au slanted columnar heterostructures. In addition, coupled-plasmon-like and inter-band transition-like modes occur in the visible and ultra-violet spectral regions, respectively. We elucidate an example for the potential use of Si-Au slanted columnar heterostructures as a highly porous plasmonic sensor with optical read out sensitivity to few parts-per-million solvent levels in water.

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“…36 For example, monoclinic β-Ga 2 O 3 , which has gained attention for high power solid state transistor and switch applications, has been analyzed from the terahertz to the vacuum ultra violet spectral regions for its complete phonon mode and free charge carrier properties, [37][38][39][40] and electronic band-to-band transitions as well as its static and highfrequency dielectric constants, indices of refraction, and extinction coefficients. [41][42][43][44][45] A similar analysis procedure resulted in complete sets of phonon modes for monoclinic scintillator material cadmium tungstate (CdWO 4 ) 46 and YSO. 47 To date, the only generalized spectroscopic ellipsometry investigation of LSO was reported by Jellison et al, and the four real-valued dielectric function tensor spectra were obtained in the spectral range from 200 nm to 850 nm.…”

Section: Introductionmentioning

confidence: 99%

Infrared active phonons in monoclinic lutetium oxyorthosilicate

Stokey

Mock

Korlacki

et al. 2020

Journal of Applied Physics

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A combined generalized spectroscopic ellipsometry measurement and density functional theory calculation analysis is performed to obtain the complete set of infrared active phonon modes in Lu2SiO5 with monoclinic crystal structure. Two different crystals, each cut perpendicular to a different crystal axis are investigated. Ellipsometry measurements from 40 -1200 cm −1 are used to determine the frequency dependent dielectric function tensor elements. The eigendielectric displacement vector summation approach and eigendielectric displacement loss vector summation approach both augmented with anharmonic lattice broadening parameters proposed recently for low-symmetry crystal structures [A. Mock et al., Phys. Rev. B 95, 165202 (2017)] are applied for our ellipsometry data analysis. All measured and model calculated dielectric function tensor and inverse dielectric function tensor elements match excellently. 23 Au symmetry and 22 Bu symmetry infrared active transverse and longitudinal optical modes are found. We also determine the directional limiting modes and the order of the phonon modes within the monoclinic plane. Results from density functional theory and ellipsometry measurements are compared and nearly perfect agreement is observed. We further compare our results to those obtained recently for the monoclinic crystal Y2SiO5, which is isostructural to Lu2SiO5 [A. Mock et al., Phys. Rev. B 97, 165203 (2018)]. We find that the lattice mode behavior of monoclinic Lu2SiO5 is qualitatively identical with Y2SiO5, and differs only quantitatively. We anticipate that members of the isostructural group of monoclinic symmetry oxyorthosilicates such as Dy2SiO5 or Yb2SiO5 will likely behave very similar in their phonon mode properties as reported here for Lu2SiO5.

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Anisotropy, band-to-band transitions, phonon modes, and oxidation properties of cobalt-oxide core-shell slanted columnar thin films

Abstract: , band-to-band transitions, phonon modes, and oxidation properties of cobalt-oxide core-shell slanted columnar thin films" (2016). Faculty Publications from the Department of Electrical and Computer Engineering. 349.

Cited by 13 publications

References 43 publications

Electrical and material properties of hydrothermally grown single crystal (111) UO2

Electrical and material properties of hydrothermally grown single crystal (111) UO2

Tunable plasmonic resonances in Si-Au slanted columnar heterostructure thin films

Infrared active phonons in monoclinic lutetium oxyorthosilicate

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