Thin-film stabilization of metastable phases in the Sm[sub 1-x]Sr[sub x]CuO[sub y] system
- Thomas J. Watson Research Center, Yorktown Heights, NY (United States)
- Universite de Caen (France)
The pulsed laser deposition (PLD) technique has been utilized for thin film synthesis of new metastable phases in the Sm[sub 1-x]Sr[sub x]CuO[sub y] (y = 2.5-0.5x + [delta]) system. The films are grown epitaxially on (100)-oriented SrTiO[sub 3] substrates in a low-pressure oxygen ambient with in situ monitoring using reflection high-energy electron diffraction (RHEED). X-ray diffraction and transmission electron microscopy are used for structural characterization of the films. Although the synthesis of SmCuO[sub 3-[delta]]-the structural analogue of the defect perovskites LaCuO[sub 3-[delta]] (0 [le] [delta] [le] 0.5) - have not been successful, perovskite-type phases have been stabilized with Sr substitution over a relatively wide composition range (0.4 [le] x [le] 0.66). With further increase in the Sr content, an ordered 2[radical]2a[sub p] x 2[radical]2a[sub p] x a[sub p] structure with mixed copper valence has been synthesized for x [approximately] 0.75. Finally, for terminal Sr concentrations (x [ge] 0.9), the doped infinite-layer-type SrCuO[sub 2] phases are obtained. The transport properties of the Sm[sub 1-x]Sr[sub x]CuO[sub y] films are sensitive to the oxygen concentration used during deposition and subsequent cooldown. For films cooled in 760 Torr of O[sub 2], a systematic decrease in the resistivity is observed as a function of Sr content, with the lowest resistivity and metallic temperature dependence being observed for the ordered structure. However, films with higher Sr concentrations, with the infinite-layer structure, exhibit relatively high resistivity under these annealing conditions. A significant decrease in the resistivity, along with semimetallic temperature dependence, is observed for these (Sm-doped) films when they are vacuum annealed prior to cooldown. No evidence of superconductivity has been detected in any of the Sm[sub 1-x]Sr[sub x]CuO[sub y] films down to 5 K. 19 refs., 6 figs.
- OSTI ID:
- 6768535
- Journal Information:
- Chemistry of Materials; (United States), Journal Name: Chemistry of Materials; (United States) Vol. 6:7; ISSN CMATEX; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
ANNEALING
CHALCOGENIDES
CHEMICAL PREPARATION
COHERENT SCATTERING
COPPER COMPOUNDS
CUPRATES
DIFFRACTION
ELECTRON DIFFRACTION
ELECTRON MICROSCOPY
EPITAXY
FILMS
HEAT TREATMENTS
MICROSCOPY
OXIDES
OXYGEN COMPOUNDS
RADICALS
RARE EARTH COMPOUNDS
SAMARIUM COMPOUNDS
SAMARIUM OXIDES
SCATTERING
STOICHIOMETRY
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SYNTHESIS
THIN FILMS
TRANSITION ELEMENT COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION