Surface roughness and height-height correlations dependence on thickness of YBaCuO thin films

Abstract

For high T, superconducting multilayer applications, smooth interfaces between the individual layers are required. However, in general, e.g., YBaCuO grows in a 3D screw-dislocation or island nucleation growth mode, introducing a surface roughness, in this contribution we stud) the surface layer roughness as a function of different deposition techniques as well as deposition parameters. Special attention will be paid to the increase in film roughness with increasing film thickness. For these studies we used scanning probe microscopy. From the~ experiments, we obtained an island density decreasing with a square root dependence on the film thickness. Furthermore, height-height correlations indicate that the film growth can be described by a ballistic growth process, with very limited effective surface diffusion. The correlation lengths ~: are on the order of the island size, inferring that the island size forms the mean diffusion barrier. This results in a representation of non-correlated islands, which can be considered as autonomous systems.

Temperature dependence of the surface morphology of sputtered YBa2Cu3O7films

“…This is clearly not what is observed on YBa 2 Cu 3 O 7 films where up to 15 or more different growth layers are often observed. Furthermore, studies of the surface roughness of YBa 2 Cu 3 O 7 films show that the surface roughness increases as a function of thickness [22]. These observations are in agreement with the 'rough multilayer growth' described by Trofimov et al [21] in the presence of a finite ES barrier.…”

Natural strong pinning sites in laser-ablatedYBa2Cu3O7Huijbregtse1, Dam2, Geest3 et al. 2000Phys. Rev. B943580View full textAdd to dashboardCite

“…This may also explain the fact that some authors observe an increase of the island size with the film thickness. 37…”

Secondary Phases in (001)RBa2Cu3O7-δ Epitaxial Thin Films

“…Off-stoichiometry components can be incorporated into the structure of growing RBa 2 Cu 3 O 7 - δ films as structural defects, provided the kinetics of the phase formation is slow in comparison with the deposition rate . For example, the formation of cubic perovskite (Y,Ba)CuO 3 - x with a significant cation disorder in the Y and Ba crystallographic positions and/or Y for Ba substitution was observed by XRD, if the film growth was carried out at reduced deposition temperatures. − Too high deposition temperatures and/or too low deposition p (O 2 ) values may also be the reason for R/Ba cation disorder as well as related crystallographic vacancies, mainly in the apical oxygen site. , In this case, p (O 2 )− T deposition conditions approach the instability border of RBa 2 Cu 3 O 7 - δ , or even lie outside the area of thermodynamic stability. , Apart from point defects and substitution, off-stoichiometry cations may also be incorporated into the film structure due to the formation of extended defects, such as Y 2 Ba 4 Cu 7 O 15 - δ or YBa 2 Cu 4 O 8 structural fragments, anti-phase boundaries, and stacking faults. − The optimal p (O 2 )− T growth conditions, with respect to the films' structural quality and superconducting properties, have often been reported to be located near the equilibrium line between CuO and Cu 2 O oxides. , …”