Optical properties study of high-throughput horizontal composition gradient FeSe1-xTex thin film based on ellipsometry

Abstract

The high-throughput superconductivity research model can effectively accelerate the material synthesis and physical characterization process. It can rapidly form a database of materials and reveal the hidden key physical laws, which provides significant assistance to the research of superconducting materials, especially the exploration of superconductivity mechanism. In this work, FeSe1-xTex thin film with spread composition was grown by combined laser molecular beam epitaxy, the third generation combined thin film preparation technique. The film thickness and surface morphology were obtained by atomic force microscopy, which showed that the sample surface was relatively smooth. In addition, we measured the distribution of critical elements and c-axis lattice constants within the different microzones along the direction of composition variation on the surface of the film, by X-ray photoelectron spectroscopy and X-ray diffraction, respectively, which verified that the film was prepared in accordance with a continuous composition gradient. Based on this, nine microzones of the film were tested using the ellipsometer equipped with a focused light spot. The dispersion model of the FeSe1-xTex layer was established using the Drude-Lorentz oscillator, and the optical constants of the film with horizontal composition gradient were obtained by inversion and fitting of the data within each microzone. The results indicate that the FeSe1-xTex thin film shows an obvious composition-dependent optical property. Our work reports the optical constants of FeSe1-xTex composition-spread thin film by using a nondestructive and accurate method, spectroscopic ellipsometry, which enriches the database of this material. This work may provide a reference for establishing the correlation between the optical and superconducting properties of FeSe-based superconductors.