Structural, optical and electrical properties of YbInSe thin films

In this work, the compositional, the structural, the vibrational, the optical and the electrical characterizations of the YbInSe compound are investigated by means of energy dispersion X-ray analysis, scanning electron microscopy and X-ray diffraction, Raman spectroscopy, ultraviolet-visible light spectrophotometry, impedance spectroscopy and temperature dependent electrical conductivity, respectively. The 300 nm thick YbInSe films which were prepared by the co-evaporation of the source materials under a vacuum pressure of 10(-5) mbar, are observed to exhibit nanocrystalline clusters of size of 27 nm regularly distributed among an amorphous structure. The most intensive Raman active lines are observed at 150 and 254 cm(-1). In addition, the optical analysis has shown that the films exhibit a direct forbidden electronic transitions type energy band gap of 1.07 eV. The optical transitions are associated with interband tail states of width of 0.28 eV. Moreover, the real and imaginary parts of dielectric spectra which were analyzed in the frequency range of 270-1000 THz, were analyzed in accordance with the single oscillator and the Lorentz models, respectively. The modeling allowed determining the oscillator and dispersion energies, the terahertz free carrier scattering time, the free holes effective mass, the carrier density, the drift mobility and the reduced resonant frequency for the YbinSe films. In the electronic part of study, the temperature dependent dc electrical conductivity analysis, indicated the domination of the variable range hopping transport mechanism below 335 K, the thermal excitation of charge carriers in the range of 337390 K and the extrinsic-intrinsic transition property at 390 K. The ac conductivity spectra which were recorded in the frequency range of 10-1500 MHz, revealed the domination of the correlated barrier hopping of free carriers between pairs of localized states at the Fermi level. (C) 2016 Elsevier B.V. All rights reserved.