B. O. Wells

Suppression of superconductivity in FeSe films under tensile strain

We have studied the effect of tensile strain on the superconductivity in FeSe films. 50, 100, and 200 nm FeSe films were grown on MgO, SrTiO3, and LaAlO3 substrates by using a pulsed laser deposition technique. X-ray diffraction analysis showed that the tetragonal phase is dominant in all of our FeSe films. The 50 nm FeSe films on MgO and SrTiO3 are under tensile strain, while the 50 nm FeSe film on LaAlO3 and the other thick FeSe films are unstrained. Superconducting transitions have been observed in unstrained FeSe films with Tonset≈8 K, which is close to the bulk value. However, no sign of superconductivity has been observed in FeSe films under tensile strain down to 5 K. This is evidence to show that tensile strain suppresses superconductivity in FeSe films.

Phase coexistence near a morphotropic phase boundary in Sm-doped BiFeO3 films

We have investigated heteroepitaxial films of Sm-doped BiFeO3 with a Sm-concentration near a morphotropic phase boundary. Our high-resolution synchrotron x-ray diffraction, carried out in a temperature range of 25 to 700 °C, reveals substantial phase coexistence as one changes temperature to crossover from a low-temperature PbZrO3-like phase to a high-temperature orthorhombic phase. We also examine changes due to strain for films exhibiting anisotropic misfit between film and substrate. Additionally, thicker films exhibit a substantial volume collapse associated with the structural transition that is suppressed in thinner films.

STRUCTURAL PHASE TRANSITION IN EPITAXIAL PEROVSKITE FILMS

Three different film systems have been systematically investigated to understand the effects of strain and substrate constraint on the phase transitions of perovskite films. In

Resistivity of V2O3 thin films deposited on a-plane (110) and c-plane (001) sapphire by pulsed laser deposition

\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}

Stress Induced Monoclinic Phase in Epitaxial BaTiO3 on MgO

films, the phase transition temperature

Magnetic phase separation in SrCoOx (2.5 ≤ x ≤ 3)

{T}_{c}

Lattice strain in epitaxial BaTiO3 thin films

was determined by monitoring the superlattice peaks associated with rotations of

Nanostructured arrays of semiconducting octahedral molecular sieves by pulsed-laser deposition

\mathrm{Ti}{\mathrm{O}}_{6}

Separation of the Strain and Finite Size Effect on the Ferromagnetic Properties of La0.5Sr0.5CoO3 Thin Films

octahedra. It is found that

Superconductivity Induced in Iron Telluride Films by Low-temperature Oxygen Incorporation

{T}_{c}