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Your search keyword '"Grazul, John L."' showing total 14 results
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14 results on '"Grazul, John L."'

2. Atomic-scale imaging of nanoengineered oxygen vacancy profiles in SrTiO3

Author

Muller, David A., Nakagawa, Naoyuki, Ohtomo, Akira, Grazul, John L., and Hwang, Harold Y.

Subjects
Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Author(s): David A. Muller (corresponding author) [1, 2]; Naoyuki Nakagawa [1, 3]; Akira Ohtomo [1, 4]; John L. Grazul [1, 2]; Harold Y. Hwang [1, 3, 5] At the heart [...]

Published
2004
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7. High-mobility electrons in SrTiO_3_ heterostructures

Author

Hwang, Harold Y., Ohtomo, Akira, Nakagawa, Naoyuki, Muller, David A., and Grazul, John L.

Subjects
Materials science, Condensed matter physics, business.industry, Delta doping, Oxide, Heterojunction, Electron, Condensed Matter Physics, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Electron transport chain, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, chemistry.chemical_compound, Condensed Matter::Materials Science, chemistry, Modulation, Condensed Matter::Superconductivity, Optoelectronics, business, Deposition (law), Perovskite (structure)
Abstract

Recent advances in thin-film deposition techniques have enabled the growth of perovskite oxide heterostructures with near-atomic precision. We have been exploring the feasibility of creating two-dimensional electron gases in SrTiO 3 heterostructures. Three different approaches are presented here: atomic-scale delta doping, direct modulation of the oxygen stoichiometry, and mobile charge arising at a polar/non-polar heterointerface.

Published
2004

8. Artificial charge-modulationin atomic-scale perovskite titanate superlattices

Author

Ohtomo, Akira, Muller, David A., Grazul, John L., and Hwang, Harold Y.

Subjects
Length scale, Physics, Condensed Matter::Materials Science, Charge ordering, Multidisciplinary, Condensed matter physics, Hall effect, Superlattice, Nanotechnology, Heterojunction, Electronic structure, Titanate, Perovskite (structure)
Abstract

The nature and length scales of charge screening in complex oxides are fundamental to a wide range of systems, spanning ceramic voltage-dependent resistors (varistors), oxide tunnel junctions and charge ordering in mixed-valence compounds(1-6). There are wide variations in the degree of charge disproportionation, length scale, and orientation in the mixed-valence compounds: these have been the subject of intense theoretical study(7-11), but little is known about the microscopic electronic structure. Here we have fabricated an idealized structure to examine these issues by growing atomically abrupt layers of LaTi3+O3 embedded in SrTi4+O3. Using an atomic-scale electron beam, we have observed the spatial distribution of the extra electron on the titanium sites. This distribution results in metallic conductivity, even though the superlattice structure is based on two insulators. Despite the chemical abruptness of the interfaces, we find that a minimum thickness of five LaTiO3 layers is required for the centre titanium site to recover bulk-like electronic properties. This represents a framework within which the short-length-scale electronic response can be probed and incorporated in thin-film oxide heterostructures.

Published
2002

13. Atomic-scale imaging of nanoengineered oxygen vacancy profiles in SrTiO3.

Author

Muller, David A., Nakagawa, Naoyuki, Ohtomo, Akira, Grazul, John L., and Hwang, Harold Y.

Subjects
STOICHIOMETRY, PHYSICAL & theoretical chemistry, FERROELECTRICITY, POLARIZATION (Electricity), ELECTRIC properties of crystals, DIELECTRICS
Abstract

At the heart of modern oxide chemistry lies the recognition that beneficial (as well as deleterious) materials properties can be obtained by deliberate deviations of oxygen atom occupancy from the ideal stoichiometry. Conversely, the capability to control and confine oxygen vacancies will be important to realize the full potential of perovskite ferroelectric materials, varistors and field-effect devices. In transition metal oxides, oxygen vacancies are generally electron donors, and in strontium titanate (SrTiO3) thin films, oxygen vacancies (unlike impurity dopants) are particularly important because they tend to retain high carrier mobilities, even at high carrier densities. Here we report the successful fabrication, using a pulsed laser deposition technique, of SrTiO3 superlattice films with oxygen doping profiles that exhibit subnanometre abruptness. We profile the vacancy concentrations on an atomic scale using annular-dark-field electron microscopy and core-level spectroscopy, and demonstrate absolute detection sensitivities of one to four oxygen vacancies. Our findings open a pathway to the microscopic study of individual vacancies and their clustering, not only in oxides, but in crystalline materials more generally. [ABSTRACT FROM AUTHOR]

Published
2004
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14. Atomic-scale imaging of nanoengineered oxygen vacancy profiles in SrTiO3.

Author

Muller, David A., Nakagawa, Naoyuki, Ohtomo, Akira, Grazul, John L., and Hwang, Harold Y.

Subjects
*STOICHIOMETRY, *PHYSICAL & theoretical chemistry, *FERROELECTRICITY, *POLARIZATION (Electricity), *ELECTRIC properties of crystals, *DIELECTRICS
Abstract

At the heart of modern oxide chemistry lies the recognition that beneficial (as well as deleterious) materials properties can be obtained by deliberate deviations of oxygen atom occupancy from the ideal stoichiometry. Conversely, the capability to control and confine oxygen vacancies will be important to realize the full potential of perovskite ferroelectric materials, varistors and field-effect devices. In transition metal oxides, oxygen vacancies are generally electron donors, and in strontium titanate (SrTiO3) thin films, oxygen vacancies (unlike impurity dopants) are particularly important because they tend to retain high carrier mobilities, even at high carrier densities. Here we report the successful fabrication, using a pulsed laser deposition technique, of SrTiO3 superlattice films with oxygen doping profiles that exhibit subnanometre abruptness. We profile the vacancy concentrations on an atomic scale using annular-dark-field electron microscopy and core-level spectroscopy, and demonstrate absolute detection sensitivities of one to four oxygen vacancies. Our findings open a pathway to the microscopic study of individual vacancies and their clustering, not only in oxides, but in crystalline materials more generally. [ABSTRACT FROM AUTHOR]

Published
2004
Full Text
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