Determining the crystal symmetry of epitaxial Tl-2201 thin films by X-ray diffraction

Abstract

The crystal symmetry of epitaxial Tl-2201 films on LaAlO 3 and SrTiO 3 substrates is investigated by X-ray diffraction. In the case of Tl 1.85Ba 2CuO 6 film, a φ-scan of the (1 1 10) reflection showed four diffraction peaks separated by 90.00±0.02°. A 2 θ-scan of the same reflection exhibited a single peak. 2 θ− ω- and φ-scans of the corresponding reflection in Tl 2.04Ba 2CuO 6 show splitting and broadening of the diffraction peaks indicating an orthorhombic distortion. The effect of errors in film alignment on the φ-scan and 2 θ− ω-scans is discussed. A periodic function, δ= a+ bsin( β− φ), was used to correct the φ-scan measurements. The influence of lattice mismatch between film and substrate on the structural symmetry of the films is discussed.