MICROSTRUCTURE OF ULTRATHIN FILMS OF YBA2CU3O7-DELTA ON MGO. STREIFFER, S., LAIRSON, B., EOM, C., CLEMENS, B., BRAVMAN, J., & GEBALLE, T. PHYSICAL REVIEW B, 43(16, A):13007-13018, JUN 1, 1991.
doi  abstract   bibtex   
The microstructure of ultrathin films of YBa2Cu3O7-delta on MgO has been studied for film thicknesses from 1.2 to 12 nm. For thicknesses of 1.2, 2.4, and 7.2 nm, the films appear to be in the tetragonal modification and consist of interconnected, low-aspect-ratio (thickness to diameter ratio less-than-or-equal-to 0.1) nuclei. The dominant growth mechanism is propagation in the a-b plane of one-unit-cell-high ledges by attachment onto the ledge face, resulting in a large difference between the c- and a-direction growth rates and forcing a two-dimensional appearance in the initial deposition. The 12-nm films are also tetragonal but provide complete coverage of the substrate. Their microstructure has passed the initial nucleation and growth stage and is similar to that of standard (thickness greater-than-or-equal-to 100 nm) films. By analysis of the free energy of the tetragonal-to-orthorhombic transition occurring upon cooling from the deposition temperature, we note a film-thickness dependence of the energy available for the transition. We postulate this as an explanation for the lack of orthorhombicity in ultrathin films.
@article{ ISI:A1991FP63100039,
Author = {STREIFFER, SK and LAIRSON, BM and EOM, CB and CLEMENS, BM and BRAVMAN,
   JC and GEBALLE, TH},
Title = {{MICROSTRUCTURE OF ULTRATHIN FILMS OF YBA2CU3O7-DELTA ON MGO}},
Journal = {{PHYSICAL REVIEW B}},
Year = {{1991}},
Volume = {{43}},
Number = {{16, A}},
Pages = {{13007-13018}},
Month = {{JUN 1}},
Abstract = {{The microstructure of ultrathin films of YBa2Cu3O7-delta on MgO has been
   studied for film thicknesses from 1.2 to 12 nm. For thicknesses of 1.2,
   2.4, and 7.2 nm, the films appear to be in the tetragonal modification
   and consist of interconnected, low-aspect-ratio (thickness to diameter
   ratio less-than-or-equal-to 0.1) nuclei. The dominant growth mechanism
   is propagation in the a-b plane of one-unit-cell-high ledges by
   attachment onto the ledge face, resulting in a large difference between
   the c- and a-direction growth rates and forcing a two-dimensional
   appearance in the initial deposition. The 12-nm films are also
   tetragonal but provide complete coverage of the substrate. Their
   microstructure has passed the initial nucleation and growth stage and is
   similar to that of standard (thickness greater-than-or-equal-to 100 nm)
   films. By analysis of the free energy of the tetragonal-to-orthorhombic
   transition occurring upon cooling from the deposition temperature, we
   note a film-thickness dependence of the energy available for the
   transition. We postulate this as an explanation for the lack of
   orthorhombicity in ultrathin films.}},
DOI = {{10.1103/PhysRevB.43.13007}},
ISSN = {{0163-1829}},
ResearcherID-Numbers = {{Streiffer, Stephen/A-1756-2009
   Eom, Chang-Beom/I-5567-2014}},
Unique-ID = {{ISI:A1991FP63100039}},
}

Downloads: 0