Epitaxial growth and optical properties of Sr_2-xCa_xNaNb₅O₁₅thin films by pulsed laser deposition

High-quality Sr2-xCaxNaNb5O15(SCNN) thin films have been epitaxially grown on MgO(0 0 1) substrates by pulsed laser deposition (PLD) technique for the first time. The thickness of the films is in the range of 600-800 nm. Their structural qualities and surface morphology were studied by X-ray diffraction and scanning electron microscopy. θ-2θ scans indicate that single crystalline SCNN layers with (0 0 1) orientation perpendicular to the substrate plane were obtained. φ-scans on the (221) plane confirm that the unit cell of SCNN films rotates in the plane of the film by ±17.8° with respect to the MgO substrate unit cell. Optical studies by optical transmittance measurements were carried out in the spectral range of 200-900 nm. In the analysis of the measured optical transmittance spectra, a single electronic oscillator model was adopted to represent the refractive index and the extinction coefficient of the SCNN films. Our results suggest that PLD is a promising technique in preparing high-quality epitaxial SCNN films for electro-optic device applications.