Changes in the Crystal Lattice Parameters of Bismuth Films on Substrates with Different Thermal Expansion

Due to the sensitivity of the electronic structure of semi-metals to small distortions of the crystal lattice, the study of the electrical and galvanomagnetic properties of bismuth films requires taking into account the deformation that occurs in the film-substrate system due to the difference in the thermal expansion of the film and substrate materials. The magnitude of these deformations plays an important role in analyzing the temperature dependencies of the transport properties of charge carriers. The paper presents an experimental study of the magnitude of deformation of bismuth films on various substrates at 300 and 77 K using X-ray diffraction. Changes in the lattice constant c$c$ of crystallites, the trigonal axis of which is perpendicular to the film plane, depending on the substrate material, are obtained. A comparison between the assessment of the deformation of these crystallites in the film plane based on Hooke's law and the difference in the coefficients thermal expansion of the film and substrate materials is made. Sensitivity of the electronic structure of semimetals to small distortions of the crystal lattice requires taking into account the film deformation due to the difference in the thermal expansion of the film and substrate materials. In the paper an attempt is made to use routine X-ray diffraction study to analysis of the deformation magnitude of bismuth films and compared the results with calculation, based on coefficients of thermal expansion difference. image