Infrared lattice vibrations of CdIn2Se4

Infrared reflectivity spectra of CdIn₂Se₄ single crystals are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹ for the polarization directions E ⟂ c and E ‖[112]. The spectra reveal two vibrational modes with nearly the same frequencies for both polarization directions. The frequencies of the modes with highest energy compare well with the corresponding mode frequencies in ZnIn₂Se₄, CuInSe₂ and AgInSe₂. It is concluded that these modes are sphalerite-like in nature and that their frequencies are essentially determined by the properties of the In Se bond.     

Infrared Optical Characterization of Thermally Oxidized CuInSe2 Single Crystals

Infrared reflectivity spectra of thermally oxidized CuInSe₂ single crystals are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹. A Kramers-Kronig analysis of the spectra reveals seven vibrational modes with frequencies which agree with mode frequencies in In₂O₃. No vibrational modes due to Cu–O and Se–O bonds could be observed. The results obtained are compared with previous studies of oxidized CuInSe₂ crystals.     

Infrared optical properties of (CuGe2P3)1−x(6 Ge)x solid solutions

Infrared reflectivity spectra of (CuGe₂P₃)_1−x(6 Ge)_x mixed crystals with compositions in the range x = 0.07–0.33 are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹. An analysis of the spectra reveals six vibrational modes. The composition dependence of the mode frequencies and of the free carrier concentration and mobility is given and compared with infrared optical data for CuGe₂P₃.     

Study of the complex vibrational spectra of natural mesolite

The vibrational spectra of the natural zeolite, mesolite (locality Akureyri-Island) were measured in the infrared (200—400 cm⁻¹) and the far infrared — FIR (40—400 cm⁻¹) regions: the infrared reflectance (200—1400 cm⁻¹) and Raman scattering (50—3600 cm⁻¹) spectra of the polycrystalline material were also measured. The Schimanouchi GCCC, BGLZ, and LSMA programs were used to calculate the force constants and vibrational frequencies of the Si O, Al O, O H, cation-oxygen, O Si O, O Al O, H O H bonds and libration of H₂O and Si(Al) O Si on the basis of the symmetry coordinates. The KKK-1 program (Petzelt, Kroupa) was used to calculate the dispersion curves of the complex refractive index for both parts of the complex dielectric permittivity in the whole measured wavenumber region. The bands in the spectra were assigned to the vibrations of the individual bonds and structural groups of the mesolite on the basis of theoretical calculations.     

Comparative infrared lattice vibration study of LiGaO2 and LiInO2 (I) experimental results

Infrared reflectivity spectra of LiGaO₂ and LiInO₂ samples pressed from powdered material are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹. The optical mode frequencies found for LiGaO₂ agree with measurements on single crystals. In LiInO₂ four vibrational modes are found. Comparing the results for LiGaO₂ some conclusions are made with regard to the Li O bond related vibrational modes.     

Infrared Lattice Vibrations in NaGaO2

Infrared reflectivity spectra of NaGaO₂ samples prepared from powdered material are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹. An analysis of the spectra with the Kramers-Kronig method reveals 16 vibrational modes. From a comparison of the results for NaGaO₂ with previous measurements on the isostructural compound LiGaO₂ conclusions are made with regard to the Ga–O and Na–O bond related vibrational modes.     

Infrared Absorption Spectra of CdIn2Te4

Transmittance and reflectance spectra of CdIn₂Te₄ are measured in the wavenumber range from 200 to 4000 cm^–1. In the range from 200 to 400 cm^–1 the spectra are governed by two-phonon combination mode absorptions. In the wavenumber range above 400 cm^–1 absorption coefficients below 1 cm^–1 and a constant reflectivity of about 0.21 are found.     

Infrared optical characterization of epitaxial layer – substrate systems (II). Experimental results for AlxGa1−xAs/GaAS

Infrared reflectance and transmittance spectra and Raman scattering spectra of the epitaxial layer-substrate system Al_xGa_1−xAs/GaAs with compositions in the range x = = 0.08–0.49 are measured in the wavenumber range from 40 to 4000 cm⁻¹. In analysing the spectra in terms of the respective theoretical relations for an optical two-layer system the thickness of the layers, the optical mode characteristics and the free carrier parameters are determined. From a comparison with existing literature data for Al_xGa_1−xAs it is concluded that infrared optical measurements on epitaxial layer-substrate systems can be successfully employed to evaluate the material parameters of epitaxial layers with thicknesses down to a few micrometers.     

Infrared lattice vibrations in CuGe2P3

Infrared reflectivity spectra of CuGe₂P₃ single crystals are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹. From an analysis of the spectra the parameters of five vibrational modes are determined. The results are discussed in terms of the Keating model and are compared with lattice vibrational data for ZnGeP₂, CdGeP₂, and CuSi₂P₃.     

Vibrational properties of CdGa2S4

Polarization-dependent infrared reflectivity spectra of CdGa₂S₄ are measured at 300 K in the wavenumber range from 180 to 500 cm⁻¹. The analysis of the spectra yields three E and four B modes in this frequency range. The results are compared with previously published data and a final identification of the infrared active modes in CdGa₂S₄ is proposed. It is shown that the two-phonon absorption spectra of CdGa₂S₄ can be interpreted in terms of zone-centre two-phonon combination modes. The relation between the lattice vibrational properties of chalcopyrite and defect-chalcopyrite compounds is discussed.     

Infrared lattice vibrations in Cu2GeSe3

Infrared reflectivity spectra of Cu₂GeSe₃ are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹. From an analysis of the spectra the parameters of four vibrational modes are determined. The experimental results are compared with predictions from group theory. From a comparison of the results for Cu₂GeSe₃ with the vibrational characteristics of other chalcogenides it follows that the force constants of cation-chalcogen bonds increase with increasing valence of the cation.     

Infrared reflectivity of ZnIn2Te4

Infrared reflectivity spectra of ZnIn₂Te₄ single crystals are measured at room temperature in the wavenumber range from 170 to 4000 cm⁻¹. The spectra reveal a single vibrational mode the frequency of which compares well with the frequencies of the high-energy infrared active modes in HgIn₂Te₄, CuInTe₂ and AgInTe₂. It is concluded that these modes are sphalerite-like in nature and that they are essentially determined by the properties of the In—Te bond.     

Lattice Vibrations and Interatomic Forces in LiInS2

Infrared reflectivity spectra of LiInS₂ are measured at room temperature in the wave-number range from 180 to 4000 cm⁻¹. The parameters of four optical modes are determined by a dispersion analysis of the spectra. From the interatomic force constants determined from the sphalerite-like modes in the lattice vibration spectrum it follows that the Li–S bond is considerably weaker than the In S bond.     

Electrical and infrared optical properties of CdIn2S4 single crystals grown by chemical transport

Single crystals of CdIn₂S₄ were grown by chemical transport with iodine as transporting agent using different transporter concentrations and temperature gradients. It is found that the electron concentration increases with increasing transporter concentration and decreases after annealing in a sulphur atmosphere. Infrared reflectivity and absorption spectra are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹ in order to determine the optical mode parameters of the compound and to evaluate the scattering mechanism of the electrons from the free carrier absorption. Lattice scattering is found to be predominant at room temperature for electron concentrations below about 4 · 10¹⁷ cm⁻³.     

Multimode phonon structure of Be‐containing II ‐ VI mixed crystals determined by IR spectroscopic ellipsometry

Spectroscopic ellipsometry in the infrared spectral range 250‐5000 cm^‐1 is used for analysis of the dielectric response of Zn_1‐x‐yBe_xMg_ySe and Zn_1‐x‐yBe_xMn_ySe crystals grown by a high‐pressure Bridgman method. Ellipsometric spectra display features in the spectral range 390‐500 cm^‐1 associated with BeSe‐type phonon modes. In the optical spectra of Zn_1‐x‐yBe_xMg_ySe crystals both BeSe‐type and MgSe‐type lattice absorption bands are detected. The MgSe‐like modes are located at approximately 300 cm^‐1. The complex dielectric functions can be reproduced using a model with two or three and one or two classical damped oscillators corresponding to the BeSe‐like and the MgSe‐like transverse‐optical phonon modes, respectively. The frequencies of longitudinal‐optical phonons have been derived from the dielectric loss functions. A red‐shift of the BeSe‐like phonons frequencies with a mean rate 0.42 cm^‐1 (0.50 cm^‐1) per mole percent of Mg (Mn) incorporated to the alloy has been found for examined concentration range x, y ≤ 0.25. A noticeable damping the intensities of BeSe‐type modes with increasing fraction of Mg and Mn dopant is observed in comparison to the strengths of BeSe‐type modes in Zn_1‐xBe_xSe crystals. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

EPR and Optical Absorption Spectra of Cr3+ Ions in Lithium Sulphate Single Crystals

Optical absorption and EPR spectra of Li₂SO₄ · H₂O crystals doped with Cr³⁺ are studied at liquid nitrogen temperature. The bands are found in absorption spectra with maxima about 17000, 23 800 and 37 200 cm⁻¹, assigned to the ⁴A₂ → ⁴T₂, ⁴A₂ → ⁴T₁ and ⁴A₂ → ⁴T₁ (⁴P) transitions, respectively. The crystal field theory parameters were determined and appeared to be as follows: Dq = 1700 cm⁻¹, B = 667 cm⁻¹, C = 3002 cm⁻¹. The lines resulting from Cr³⁺ ions are found in EPR spectra. All lines are doublets, which is indicative of presence of two magnetically unequivalent centre positions, and have the hyperfine structure resulting from interaction of the unpaired electron spin with Cr⁵³ isotope nucleus. Centres are oriented in such a way, that z-axes, corresponding to two centre positions, are situated at both sides of a-axis at an angle of about 3°. Spin Hamiltonian parameters were found as follows: g_x = 1.985, g_y = 1.984, g_z = 1.988, D = 0.130 cm⁻¹, E = 0.016 cm⁻¹, |A| = 17.8 · 10⁻⁴ cm⁻¹.     

Infrared Lattice Vibrations of TI3AsS4

Infrared reflectivity spectra of TI₃AsS₄ single crystals are measured at room temperature in the wavenumber range from 30 to 4000 cm⁻¹ for the polarization directions E ‖ c and E ‖ a. An analysis of the spectra with the Kramers-Kronig method reveals 10 infrared active modes for each of the polarization directions. On the basis of theoretical estimates the modes due to TI-S and As–S bond vibrations are identified.     

Infrared lattice vibrations of PbGa2S4

Infrared reflectivity spectra of PbGa₂S₄ single crystals are measured at room temperature in the wavenumber range from 30 to 4000 cm⁻¹ for the polarization directions E ∥ c and E ∥ b. The frequencies of 13 B_1u modes and 11 B_2u modes are derived from the spectra. The results are compared with previous studies and with lattice vibration data of ternary chalcopyrite and defect-chalcopyrite compounds.     

Infrared studies of Se-based polynary chalcogenide glasses (II): YxZxSe100−2x (Y = Ge,As; Z = As,Te)

The infrared (IR) absorption spectra for Y_xZ_xSe_100?2x glasses (Y = Ge, As;Z = As, Te), x = 2.5 and 5.0 are measured in the wavenumber region 700-60 cm^?1 at room temperature. These IR spectra are explained by comparing with the IR spectra already reported for the binary glasses such as Ge–Se, As–Se and Se–Te. In Ge_xAs_xSe_100-2x glasses (x ? 5.0), the main spectral features as well explained by both the spectra of Ge_xSe_100?x and As_xSe_100?x glasses. Main structural units in these glasses are considered to be GeSe₄ tetrahedra and AsSe₃ pyramids, and Se₈ rings and Se_n chains which are the units in pure glassy Se. In Ge_xTe_xSe_100?2x glasses (x ? 5.0) and IR band which cannot be explained by either the spectra of Ge_xSe_100?x or Se_100?xTe_x glasses appears at 210 cm^?1. This band is considered to be due to Ge–Te bonds. The IR spectra of As_xTe_x Se_100?2x glasses (x ? 5.0) are well explained by both the spectra of As_xSe_100?x and Se_100?xTe_x glasses. It is concluded that As and Te atoms combine with Se atoms in the forms of AsE₃ pyramids and Se₅Te₃ mixed rings, respectively.     

Infrared Lattice Vibrations of CdGa2Te4

Infrared reflectivity spectra of CdGa₂Te₄ crystals are measured at room temperature in the wavenumber range from 180 to 600 cm⁻¹ for the polarization directions E ⊥ c and E ‖ [111]. The frequencies of two E modes and two B modes are derived from the spectra. The frequencies of the modes with highest energy compare well with those of the corresponding modes in CuGaTe₂ and AgGaTe₂ which confirms the sphalerite-like nature of these modes.