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0Structural and optical properties of PbSe(S) thin films
S.N. Yasinova1*, S.I. Mekhtiyeva2, M.H. Huseynaliyev1, R.I. Alekberov2
1- The Ministry of Science and Education of Azerbaijan, Institute of Natural Resources, H.Aliyev ave. 76,
AZ7000, Nakhchivan
2- The Ministry of Science and Education of Azerbaijan, Institute of Physics named after Academician Hasan
Abdullayev, G. Javid ave 131, AZ1143 Baku
* sara.novruzova@yahoo.com
The purpose of this work is to analyze the changes in the structural properties of lead chalcogenides (PbSe and PbS) thin films obtained by chemical bath deposition and the mechanisms of their influence on Raman scattering. Studies show that transverse and surface phonon modes are usually not observed due to symmetry constraints [1]. The main reason for the mentioned uncertainty is the observation of rapid photooxidation processes in thin layers of PbS and PbSe under the influence of laser radiation applied to observe Raman scattering [2]. In particular, while weak Raman scattering is expected to be observed in the region of relatively low wave numbers (154, 205 and 454 cm-1) in PbS, photooxidation processes occurring on the surface of thin films under the influence of a laser beam artificially enhance the Raman scattering signal [2]. It was determined that as a result of semi-substitution of selenium with sulfur, along with the increase in the size of the nanoparticles, the bond within the nanoparticles is strengthened due to the chemical activity and high bond energy of the sulfur atoms. As the elastic force constant (k) increases as a result of the increase in bond connectivity, the frequency of the Raman active oscillation modes expressed below, based on the molecular structure model, increases. The crystallite sizes of nanoparticles belonging to PbSe, PbS and PbSo.sSeo.s were calculated by applying the Debye-Scherrer formula (1) given below to the results X-ray.
, 0.9X
d =- (1)
pcose v '
In formula (1), d is the crystallite size of nanoparticles, X is the wavelength of the X-ray beam (X=1.54 A), p is the half-width of the sharp maxima described in the X-ray diffraction scattering curves of the samples and 8 is the Bragg reflection angle. The results of X-ray diffraction scattering show that the crystallite sizes found in thin layers of PbSo.sSeo.5 are larger and vary in the range of 17.9^30.8 nm.
[1] S. Hoomi, R. Yousefi, F. Jamali-Sheini, A. Saaedi, M. Cheraghizade, W.J. Basirun, N.M. Huang, Large-scale and facile fabrication of PbSe nanostructures by selenization of a Pb sheet Functional Materials Letters, Vol. 8, No. 6, 1550063 (2015).
[2] M.J. Bierman, Y.K. Albert Lau, S. Jin, Hyperbranched PbS and PbSe Nanowires and the Effect of Hydrogen Gas on Their Synthesis, Nano Letters, Vol. 7, No. 9, pp. 2907-2912 (2007).
