Growth and evolution of microstructure of epitaxial YBa2Cu3O7−x ultrathin and thin films on MgO

Savvides, N.; Katsaros, A.

doi:10.1016/0921-4534(94)90473-1

Cited by 47 publications

(29 citation statements)

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“…When the layer thickness reaches the critical value, part of this strain is relieved introducing screw and edge dislocations. Similar results are found for ultrathin YBCO films on MgO substrates, 21,22 but in this case the large lattice mismatch ͑9%, a sub ϭ4.2 Å͒ induces dislocations which appear immediately after the growth of the first monolayer. On the contrary, the smaller lattice mismatch for the YBCO/ STO structure, and the greater grain size involved by the deposition technique described in this work, delay the formation of the dislocations and the first monolayers result to be highly c-axis oriented and strained along the c axis and with a lower defect density.…”

Section: ͑1͒supporting

confidence: 84%

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Microstructural and morphological analysis of ultrathin YBa2Cu3O7−x films grown by modulated magnetron sputtering on SrTiO3 substrates

Vecchio

Riccardis

Tapfer

et al. 2000

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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The defect structure, the degree of crystalline perfection and the surface roughness of HTc superconductor films are affected by the initial layer configuration at the early stage of growth. In this work we report on structural and morphological investigations of ultrathin YBa2Cu3O7−x films grown on SrTiO3 substrate. The films are fabricated by inverted cylindrical magnetron sputtering with a modified deposition process based on the modulation of sputtering power. The modulated sputtering deposition promotes a higher in-plane grain connectivity and allows us to fabricate films with a lower defect density. The structural analyses of very thin films (thickness <25 nm) are performed by using low-angle x-ray specular reflectivity, double crystal diffraction, reciprocal space mapping and atomic force microscopy. The results indicate that a total relaxation of our films occurs at layer thickness larger than 25 nm. For thinner layers a tetragonal distortion of the unit cell and no twinning are observed. The low-angle measurements show distinct Kiessig fringes revealing a smooth surface and film/substrate interface. The off-specular reflectivity measurements indicate that the surface and interface roughness across the YBa2Cu3O7−x layer are uncorrelated.

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Section: ͑1͒supporting

confidence: 84%

“…21,22,25,26 In high-T c superconductors the supercurrent regime is strongly correlated to the thickness. In thicker films the interface morphology may play a minor role promoting a bulk regime, which is rather insensitive to the boundary conditions such as roughness and thickness fluctuations.…”

Section: ͑1͒mentioning

confidence: 99%

Microstructural and morphological analysis of ultrathin YBa2Cu3O7−x films grown by modulated magnetron sputtering on SrTiO3 substrates

Vecchio

Riccardis

Tapfer

et al. 2000

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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“…In magnetron sputtering, the adatoms arriving at the substrate surface have energies in the range of 1 eV to 100 eV (equivalent temperature 10 4 K to 10 6 K). 22 Often the reaction of the condensing species is further activated by heating the substrate. Advantageously, the temperature for this in situ synthesis of crystalline films and compounds is much lower than that for the formation at thermoelectric equilibrium, e.g., at atmospheric pressure.…”

Section: Methodsmentioning

confidence: 99%

“…growth22 with very small grain size. At the lower deposition temperatures (T s = 300°C to 400°C) the films show some surface roughness and a grain size of 20 nm to 40 nm.…”

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confidence: 99%

Magnetron Deposition of In Situ Thermoelectric Mg2Ge Thin Films

Chuang

Savvides

2009

Journal of Elec Materi

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Thin films of the semiconducting compound Mg 2 Ge were deposited by magnetron cosputtering from source targets of high-purity Mg and Ge onto glass substrates at temperatures T s = 300°C to 700°C. X-ray diffraction shows that the Mg 2 Ge compound begins to form at a substrate temperature T s % 300°C. Films deposited at T s = 400°C to 600°C are single-phase Mg 2 Ge and have strong x-ray peaks. At higher T s the films tend to be dominated by a Ge-rich phase primarily due to the loss of magnesium vapor from the condensing film. At optimum deposition temperatures, 550°C to 600°C, films have an electrical conductivity r 600 K = 20 X À1 cm À1 to 40 X À1 cm À1 and a Seebeck coefficient a = 300 lV K À1 to 450 lV K À1 over a broad temperature range of 200 K to 600 K.

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“…This 3D Volmer-Weber model initial growth is of course related to the unit-cell mismatch, as the substrate network cannot run continuously into the fllm [6]. However, at the interface, the Coulombic periodic potential of both the film and the substrate tends to be accorded, as far as possible.…”

Section: Graphoepetaxymentioning

confidence: 99%

Growth of Laser Ablated YBa₂Cu₃O₇Thin Films Epitaxied on (100)MgO: Influence of In-Plane Misorientations on Low and High Frequency Properties

1997

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Tle graphoepitaxial growth of c-axis YΒa2Cu3O7 laser ablated thin films on (100)MgO induces a competition between two main in-plane orientations due to the large lattice mismatch: (100) YΒa2Cu3O7 || (100) MgO, c10 notation or (I 10) YΒa2 Cu3O7 || (100) MgO, c145 notation. The ratio of c┴45 /c┴0 in-plane orientations (η), measured by X-ray diffraction φ scans, is ranging from 0.2% to 49.7% for the films reported here. Their crystalline qualities were compared on the basis of rocking curves (Δθ), electron channelinng patterns and reflection high energy electron diffraction diagrams. The coexistence of c┴ 0 a n d G 1 4 5 d o m a i n s c r e a t e s h i g h a n g l e g r a i n b o u n d a r i e s . N o degradation of Τc , residual resistance ratio (RRR) or ΔTc is observed when η increases. In contrast, a strong correlation between microwave losses characterized by surface resistance (Rs at 10 GHz and 77 K), inductive losses S(χ") (surface of the χ" peak obtained in a.c. susccptibility at 119 Hz) and η was clearly evidenced. A minimum of losses was found for η between 3 and 6% suggesting the necessity of a low quantity of high angle grain boundaries for films optimization. Finally, some specific processes carried out recently in order to try to efficiently control η, then Rs are discussed.PACS numbers: 68.55. Jk, 73.25.+i 1. Introduction The control of the growtl of ligl quality epitaxial thin fllms of HTSC materials opens the way to a number of applications, specially in the field of microwave devices. however, working at high frequencies implies additional requirements on the dielectric properties of the substrates and, in this aspect, (100)MgO single crystal is one of the most popular. Unfortnnately, this material presents an important misfit with HTSC, meaning severe limitations in the mechanism of heteroepitaxial growth. In this paper, we will focus on the growth of YΒa2Cu3O7 (YBCO) on (100)MgO using pulsed laser deposition, thc specific defects of such films and their implication on the surface resistance RS wlich is the pertinent parameter for any microwave applications.

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Growth and evolution of microstructure of epitaxial YBa2Cu3O7−x ultrathin and thin films on MgO

Cited by 47 publications

References 44 publications

Microstructural and morphological analysis of ultrathin YBa2Cu3O7−x films grown by modulated magnetron sputtering on SrTiO3 substrates

Microstructural and morphological analysis of ultrathin YBa2Cu3O7−x films grown by modulated magnetron sputtering on SrTiO3 substrates

Magnetron Deposition of In Situ Thermoelectric Mg2Ge Thin Films

Growth of Laser Ablated YBa₂Cu₃O₇Thin Films Epitaxied on (100)MgO: Influence of In-Plane Misorientations on Low and High Frequency Properties

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Growth and evolution of microstructure of epitaxial YBa2Cu3O7−x ultrathin and thin films on MgO

Cited by 47 publications

References 44 publications

Microstructural and morphological analysis of ultrathin YBa2Cu3O7−x films grown by modulated magnetron sputtering on SrTiO3 substrates

Microstructural and morphological analysis of ultrathin YBa2Cu3O7−x films grown by modulated magnetron sputtering on SrTiO3 substrates

Magnetron Deposition of In Situ Thermoelectric Mg2Ge Thin Films

Growth of Laser Ablated YBa2Cu3O7Thin Films Epitaxied on (100)MgO: Influence of In-Plane Misorientations on Low and High Frequency Properties

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Growth of Laser Ablated YBa₂Cu₃O₇Thin Films Epitaxied on (100)MgO: Influence of In-Plane Misorientations on Low and High Frequency Properties