V. Riede

Raman spectroscopy of CuInSe2 thin films prepared by selenization

Abstract CuInSe 2 (CIS) thin films were prepared by two-step selenization at various recrystallization temperatures. The comparative analysis of crystalline properties evaluated by XRD, SEM, EDX and Raman scattering measurements is presented here. The crystallized films show Raman spectra with a dominant A 1 mode at 174 cm −1 , generally observed in I–II–VI 2 chalcopyrite compounds and an additional peak at 258 cm −1 . Relative intensity and FWHM of A 1 mode correlates with the enhancement of the structural properties of the films. The origin of 258 cm −1 mode is discussed in terms of the presence of other phase with the symmetry of lattice vibrations different than that of CuInSe 2.

INFRARED AND RAMAN SPECTRA OF CDIN2TE4

Abstract All the eight infrared active modes and two of the only Raman active modes of CdIn2Te4 are determined by infrared reflectivity and Raman scattering measurements on melt-grown polycrystalline samples. Based on a comparison with lattice vibration data for HgIn2Te4 a tentative symmetry assignment of the modes is proposed.

Band Gap Energies and Lattice Vibrations of the Lithium Ternary Compounds LiInSe2, LiInS2, LiGaSe2 and LiGaS2

The band gap energies EG of the lithium compounds have been measured by transmittance and reflectivity measurements as well as measurements of the diffuse reflectivity. At room temperature EG=2.83 eV (LiInSe2), EG=3.56 eV (LiInS2), EG=3.13 eV (LiGaSe2) and EG=3.62 eV (LiGaS2) have been obtained presupposing a direct interband transition. In a first attempt the birefringence of LiInS2 was studied by transmittance measurements. Using infrared and Raman spectroscopy the lattice vibrational properties have been investigated.

Vibrational properties of proton-implanted crystalline InP

Abstract Infrared transmission spectra of proton implanted crystalline InP exhibit local vibrational modes at 2197 and 2212 cm-1 which are ascribed to P—H bond vibrations. The dependence of the integrated absorption A of the bands due to the P—H bonds in proton-implanted InP and GaP on the proton dose D follows the relation A ∼ Dn with n ≈ 0.4. For GaP it is established that A is proportional to the mean damage density.

Growth and Characterisation of (CuInTe2)1‐x(2 ZnTe)x Solid Solution Single Crystals

The crystal structure as well as the optical properties in the band gap region of (CuInTe 2 ) 1-x (2 ZnTe) x solid solution single crystals grown by directional freezing have been studied. The lattice constants exhibit a linear dependence on crystal composition. The chalcopyrite-sphalerite phase transition was observed between x = 0.3 and x = 0.4. The variation of the band gap with respect to crystal composition can be described by a quadratic expression.

On the Optical Properties of Defect-Chalcopyrite Single Crystals: The Aluminium Compounds HgAl2Se4, CdAl2Se4 and ZnAl2Se4.

Using both infrared and Raman spectroscopy all of the optical phonon modes of the materials under investigation have been observed and assigned to the irreducible representation of the point group of the crystals. The infrared reflectivity spectra of HgAl2Se4 as well as of oriented CdAl2Se4 single crystals show five well separated optical phonon modes for both directions of polarization, behaviour which is predicted by group theory for AIIBIII2CVI4 compounds crystallizing in space group I . ZnAl2Se4 has been found to crystallize in space group I 2m with a statistical distribution of the vacancies and half the aluminium atoms at the sites 4d. In the infrared reflectivity spectra of various ZnAl2Se4 samples in comparison with HgAl2Se4 and CdAl2Se4, the low frequency mode of B symmetry is missing. The optical properties in the band gap region have been determined using polarized transmittance and reflectivity measurements and diffuse reflectivity measurements. The estimated band gap energies at room temperature are 2.20 eV, 3.05 eV and 3.30 eV for HgAl2Se4, CdAl2Se4 and ZnAl2Se4, respectively.

Infrared lattice vibration spectra of tetragonal ZnP2

Abstract Infrared reflectivity spectra of tetragonal ZnP2 are measured in the frequency range from 40 to 600 cm-1 for both polarization directions E ⊥ c and E ‖ c. The parameters of 9 E modes and 4 A2 modes are determined by a dispersion analysis of the spectra. Three additional A2 modes are detected by infrared transmission measurements. The results obtained are compared with previous Raman scattering and two-phonon combination mode spectra.

Infrared and Raman study of lattice vibrations of CuAlSe2 single crystals

Abstract The Infrared and Raman study of lattice vibrations of the chalcopyrite compound CuAlSe 2 with a complete assignment of the lattice vibrational modes is reported. Each two modes of E symmetry and one mode of B 2 symmetry have been found in the high frequency (from 250 to 400 cm −1 ), medium frequency (from 160 to 200 cm −1 ) and low frequency (from 60 to 120 cm −1 ) region of the spectrum. Violations of the selection rules of infrared activity observed for the B 1 symmetry mode of highest energy as well as the E symmetry mode of lowest energy may indicate a distortion of the crystal lattice.

Raman scattering study of GaP:N epitaxial layers

Abstract Raman spectra of VPE-grown GaP:N samples were investigated in the temperature range between 20 and 300 K, using five discrete lines of the Ar-ion laser. The nitrogen concentration ranged from 2 × 1017 to 3.3. × 1019 cm−3. Four nitrogen-related peaks were observed. While the origin of the high-frequency peak is unclear at present, the arguments are given to identify the remaining peaks with a defect-activated LO(X) mode, a nitrogen local vibrational mode, and with its first overtone, respectively.

Infrared reflectivity of Ag6Ge10P12

Abstract Infrared reflectivity spectra of p -type Ag 6 Ge 10 P 12 single crystals were measured at room temperature in the wavenumber range from 180 to 4000 cm -1 . Fits to a dielectric function including contributions from lattice oscillators and free carriers gave the parameters of five lattice vibrational modes and an effective hole mass of m p / m o = 2.3.