High misfit epitaxial growth: Superconducting YBa2Cu3O7−x thin films on (100)BaF2 substrates

Abstract

In situ epitaxial growth of YBa2Cu3O7−x superconducting thin films on (100)BaF2 substrates has been successful by an off-axis dc planar magnetron sputtering method. The zero-resistance temperatures of these thin films are about 81–84 K with transition width of 1.5 K. The characteristics of the films were examined by x-ray diffraction, reflection high energy electron diffraction, Rutherford backscattering spectroscopy ion channeling techniques, and scanning electron microscopy. The experimental results suggest that BaF2 is a promising material as substrates or buffer layers for the epitaxial growth of high Tc superconducting thin films, especially in high frequency applications. Discussions on the heteroepitaxy of the YBCO/BaF2 system are propounded.

Ferromagnetic ground state in La 0.5 Ca 0.5 MnO 3 thin films

“…These distortions are relatively very large as compared with the usual thermal contraction in such a narrow temperature range (cf. the thermal expansion coefficient of LaAlO 3 substrate is β = 0.98 × 10 −5 K −1 at room temperature [10], which is close to the value β ≈ 0.8 × 10 −5 K −1 for La 0.67 Ca 0.33 MnO 3 at T > T c [11]).…”

Improving the optical absorption of BiFeO3 for photovoltaic applications via uniaxial compression or biaxial tension

“…4 But it is within experimental limit to achieve 13% lattice mismatch using an appropriate substrate whose lattice constant is larger than that of MgO, for example, BaPaO 3 , BaThO 3 , RbCaF 3 , RbHgF 3 . 29 Experimentally, large lattice misfit has been demonstrated for other materials, for example, Wang et al 30 showed that the epitaxial YBa 2 Cu 3 O 7 films deposited on BaF 2 and Y-ZrO 2 substrates are under misfit strain of À13% and 9%, respectively.…”

Multi-beam pulsed laser deposition for advanced thin-film optical waveguides

“…Growth of thin films where there are mismatches in both lattice constants and thermal expansion coefficients between film and substrate presents a problem. While epitaxial film growth for techniques such as liquid phase epitaxy can occur for relatively large values of lattice mismatch, with values of up to 5% reported [17], for PLD growth where bonding is weaker, and epitaxy can also occur via island growth, a larger lattice mismatch of >13% has been reported [18]. On cooling from a growth temperature as high as ∼1000 • C, films may experience strain due to differing thermal expansion, resulting in bending of the structure.…”