Valentinas Lazauskas
Vilnius University
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Publication
Featured researches published by Valentinas Lazauskas.
Ferroelectrics | 2003
J. Grigas; E. Talik; Valentinas Lazauskas
The paper presents the X-ray photoelectron spectra (XPS) of the valence band and core levels of the ferroelectric SbSI single crystal. Results revealed the new phenomenon--splitting of the core levels at the phase transition temperature T cl . The XPS are measured with monochromatized Al K f radiation in the energy range 0-1400 eV and the temperature range 130-330 K. Experimentally obtained energies are compared with the results of theoretical ab initio calculations. This is the first observation of the splitting of the XPS in a ferroelectric crystal. The mechanism of the XPS splitting in SbSI crystals is discussed.
Phase Transitions | 2002
J. Grigas; E. Talik; Valentinas Lazauskas
The paper presents the X-ray photoelectron spectra (XPS) of the valence band and core levels of semiconductor ferroelectric Sb2S3 single crystals, which show weak phase transitions and anomalies of various physical properties. The XPS were measured with monochromatized Al K α radiation in the energy range 0-1450 eV and the temperature range 160-450 K. The valence band is located 0.8-7.5 eV below the Fermi level. Experimental results of the valence band and core levels are compared with the results of theoretical ab initio calculations of the molecular model of Sb2S3 crystal. The chemical shifts in Sb2S3 crystal for the Sb and S states are obtained. Results revealed that the small structural rearrangements at the phase transition T c1 = 300 K shift the Fermi level and all electronic spectrum. Also, temperature dependence of a spontaneous polarisation shifts the electronic spectra of the valence band and core levels. Specific temperature-dependent excitations in Sb 3d core levels are also revealed.
Ferroelectrics | 2009
J. Grigas; E. Talik; Valentinas Lazauskas; Yu. M. Vysochanskii; R. Yevych; M. Adamiec; V. Nelkinas
The electronic structure of the ferroelectric Sn 2 P 2 S 6 single crystal is studied by X-ray photoelectron spectroscopy in both paraelectric and ferroelectric phases. The spectra were measured with monochromatized Al Kα radiation in the energy range 0–1400 eV. Experimental energies are compared with the results of theoretical ab initio calculations of the molecular model of the crystal. The electronic structure of the valence band (VB) is revealed. Ferroelectric phase transition changes atoms charge and bonds strength, electronic structure of VB, core levels (CL) lines width and chemical shifts for the Sn, P and S states which are crystallographic plane-dependent.
Ferroelectrics | 2007
J. Grigas; E. Talik; Valentinas Lazauskas
The paper presents the X-ray photoelectron spectra (XPS) of the valence band (VB) and of the principal core levels (CL) for SbSI-type and incommensurate TlInS 2 single crystals. Form and electronic structure of the VB and CL splitting in the quasi-one-dimensional SbSI, SbSeI and BiSI, and in the incommensurate (IC) phase of TlInS 2 crystals are discussed. Experimentally obtained energies were compared with the results of theoretical ab initio calculations. Large shifts (3 ÷ 5 eV) in the CL binding energies in SbSI show a strong dependence on the surface crystallographic plane. The splitting of the CL was also obtained in the IC phase of TlInS 2 crystals.
Condensed Matter Physics | 2007
J. Grigas; E. Talik; M. Adamiec; Valentinas Lazauskas
The paper presents the X-ray photoelectron spectra (XPS) of the valence band (VB) and of the principal core levels from the (110) and (001) crystal surfaces for the quasi-one-dimensional high permittivity SbSeI single crystal isostructural to ferroelectric SbSI. The XPS were measured with monochromatized Al Ka radiation in the energy range of 0‐1400 eV at room temperature. The VB is located from 1.6 to 20 eV below the Fermi level. Experimental energies of the VB and core levels are compared with the results of theoretical ab initio calculations of the molecular model of the SbSeI crystal. The electronic structure of the VB is revealed. Shifts in the core-level binding energies of surface atoms relative to bulk ones, which show a dependency on surface crystallography, have been observed. The chemical shifts of the core levels (CL) in the SbSeI crystal for the Sb, I and Se states are obtained.
Journal of Physics: Conference Series | 2007
J. Grigas; E. Talik; Valentinas Lazauskas
The paper presents the X-ray photoelectron spectra (XPS) of the valence band (VB) and of the principal core levels (CL) for the TlInS2 and TlInSe2 single crystals. The XPS were measured with monochromatized Al Kradiation in the energy range of 0 - 1400 eV at different temperatures. The resolved splitting of XPS in the incommensurate phase of the ferroelectric semiconductor TlInS2 single crystal was obtained. The VB is located from 0.6 to 10 eV below the Fermi level. Experimental energies of the VB and CL are compared with the results of quantum mechanical ab initio calculations of the molecular model of the TlInSe2 crystal. The electronic structure of the VB and CL is described theoretically by quantum- mechanical Hartree-Fock calculations. The surface and bulk atoms influence the shape of the VB and CL, which is crystallographic plane dependent. The chemical shifts in the both crystals for the Tl, In, S and Se states are obtained.
Journal of Electron Spectroscopy and Related Phenomena | 2006
J. Grigas; E. Talik; M. Adamiec; Valentinas Lazauskas; V. Nelkinas
Lithuanian Journal of Physics | 2004
J. Grigas; E. Talik; Valentinas Lazauskas
Lithuanian Journal of Physics | 2006
Valentinas Lazauskas; V. Nelkinas; J. Grigas; E. Talik; V. Gavryushin
Archive | 2008
J. Grigas; E. Talik; Valentinas Lazauskas; Yu . M. Vysochanskii; R. Yevych; M. Adamiec; V. Nelkinas