Hasanlı, Nızamı
Measurements are made of polarized Raman scattering and infrared reflection spectra of twenty two compositions of GaS1‐xSex layer mixed crystals grown by the Bridgman method. Besides the usual one‐mode and two‐mode behaviours of phonon modes, a number of more complex dependences characterized by the appearance of additional bands in the spectra of mixed crystals are observed. Their appearance is accounted for by the uncovering of the Brillouin zone due to the disturbance of the periodicity of the crystal lattice of mixed crystals. Specifically, for modes with a low dispersion in the Brillouin zone the additional modes are interpreted as vibrations of cells having mixed compositions. A number of anomalies are revealed in the concentration dependences of intensities and frequencies of optical phonons, which are attributed to the β → γ and γ → ϵ polytype transformations at x ≈ 0.6 and x ≈ 0.97, respectively.


Optical constants of Tl4Ga3InSe8 layered single crystals
Goksen, K.; Hasanlı, Nızamı (Elsevier BV, 2007-11-15)
The optical properties of Tl(4)Ga(3)lnSe(8) layered single crystals have been studied by means of transmission and reflection measurements in the wavelength range of 500-1100 run. The analysis of the room temperature absorption data revealed the presence of both optical indirect and direct transitions with band gap energies of 1.94 and 2.20 eV, respectively. Transmission measurements carried out in the temperature range of 10-300 K revealed that the rate of change of the indirect band gap with temperature i...
Optical constants of silver and copper indium ternary sulfides from infrared reflectivity measurements
Hasanlı, Nızamı (Elsevier BV, 2016-03-01)
Infrared reflection spectra are obtained in the frequency range of 50-2000 cm(-1) for AgIn5S8 and CuIn5S8 single crystals grown by Bridgman method. All four infrared-active modes are detected, which are in full agreement with the prediction of group-theoretical analysis. Spectral dependence of optical parameters; real and imaginary parts of the dielectric function, the function of energy losses, refractive index, absorption index and absorption coefficient were calculated from reflectivity experiments. The ...
Multiphonon absorption processes in layered structured TlGaS2, TlInS2 and TlGaSe2 single crystals
IŞIK, MEHMET; Hasanlı, Nızamı; KORKMAZ ÖZKAN, FİLİZ (Elsevier BV, 2013-07-15)
The infrared transmittance and Raman scattering spectra in TlGaS2, TlInS2 and TlGaSe2 layered single crystals grown by Bridgman method were studied in the frequency ranges of 400-1500 and 10-400 cm(-1), respectively. Three, three and five bands observed at room temperature in IR transmittance spectra of TlGaS2, TlInS2 and TlGaSe2, respectively, were interpreted in terms of multiphonon absorption processes. (C) 2013 Elsevier By. All rights reserved.
FARADEV, FE; Hasanlı, Nızamı; MAVRIN, BN; MELNIK, NN (Wiley, 1978-01-01)
Polarized Raman spectra of InSe and InS crystals are obtained, the assignment of frequencies is given, and atomic displacements are found at all normal vibrations. In the InSe crystal, force constants of interaction of In‐Se and In‐In atomic planes are evaluated. It is shown that the Raman spectrum of InS has a doublet nature typical for layer crystals. The frequencies of rigid‐layer modes forbidden in the Raman spectrum are calculated in the InS crystal. It is found that interlayer force constants in the I...
BURLAKOV, VM; RYABOV, AP; YAKHEEV, MP; VINOGRADOV, EA; MELNIK, NN; Hasanlı, Nızamı (Wiley, 1989-06-01)
Low‐frequency Raman spectra of a TlInS2 single crystal in the vicinity of a ferroelectric phase transition are reported. In the ferroelectric phase a soft mode interacting with some rigid modes is observed. The temperature dependence of the soft mode frequency is found to be proportional to (Tc – T)1/2. An unusual behaviour of the rigid mode (ω = 20 cm−1) is observed. This fact is interpreted in terms of inherent lattice defects which cause nonhomogeneous broadening.
Citation Formats
N. Hasanlı, N. MELNIK, and A. RAGIMOV, “OPTICAL PHONONS IN GAS1-XSEX LAYER MIXED-CRYSTALS,” PHYSICA STATUS SOLIDI B-BASIC RESEARCH, pp. 137–147, 1983, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/42854.