E. Talik

Splitting of the XPS in Ferroelectric SbSI Crystals

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.

X-ray Photoelectron Spectroscopy of Sb2S3 Crystals

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.

Optimization of gas injection conditions during deposition of AlN layers by novel reactive GIMS method

In 2011, we proposed a novel magnetron sputtering method. It involved the use of pulsed injection of working gas for the initiation and control of gas discharge during reactive sputtering of an AlN layer (Gas Injection Magnetron Sputtering — GIMS). Unfortunately, the presence of Al-Al bonds was found in XPS spectra of the AlN layers deposited by GIMS onto Si substrate. Our studies reported in this paper proved that the synchronization of time duration of the pulses of both gas injection and applied voltage, resulted in the elimination of Al-Al bonds in the AlN layer material, which was confirmed by the XPS studies. In our opinion the most probable reason of Al-Al bonds in the AlN layers deposited by the GIMS was the self-sputtering of the Al target in the final stage of the pulsed discharge.

XPS of Electronic Structure of Ferroelectric Sn2P2S6 Crystals

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.

X-Ray Photoelectron Spectroscopy of Ferroelectrics

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.

X-ray photoelectron spectra and electronic structure of quasi-one-dimensional SbSeI crystals

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.

Characterization of PbTiO3 Nanopowders Obtained by Room Temperature Synthesis

Lead titanate nanopowders were fabricated by mechanochemical synthesis. The obtained materials were characterized by high resolution electron microscopy, X-ray excited photoelectron spectroscopy and NIR Raman scattering. The powder consists of loosely packed grains with a broad distribution of sizes between a few nm and 45 nm. The grains of sizes larger than about 30 nm exhibit well-developed crystalline structure. All grains have a shell of thin disordered/amorphous layer which was investigated by XPS. The Raman spectroscopy showed slight differences in Raman spectra of nanopowder in comparison to the bulk material: the lines related to A1(1TO), E(2TO) and A 1 (3TO) modes are shifted to lower frequencies and their spectral linewidth increase.

XPS of Impurities Influence on Electronic Structure of Sn2P2S6 Ferroelectrics

Influence of impurities of In, Te and Ge on the core level binding energies and the electronic structure of the valence band of Sn2P2S6 ferroelectric crystals was investigated by X-ray photoelectron spectroscopy together with electron spectra first-principles calculations. It was found that the indium impurity induces donor states, the tellurium impurity modifies energy structure near the top of valence band, and germanium impurity improves stereoactivity of the cation sublattice that is related to the ferroelectric phase transition nature.

Magnetic properties of manganese doped PrAlO3 monocrystalline fibres

Monocrystalline fibres of undoped PrAlO3 and PrAlO3:0.1 Mn, have been grown by the pulling-down method under nitrogen atmosphere. The as-grown crystal doped with Mn had a visible brown core surrounded by a green ring, whereas this effect was weaker for the undoped PrAlO3. A coloration of the brown core was caused by a presence of Pr4+ ions. The presence of the Pr4+ ions was confirmed by XPS and magnetic studies. The XPS chemical analysis showed the increased concentration of oxygen in the crystals with the brown core. The most probable valency of manganese is Mn4+. It is located in Al3+ sites.

XPS of incommensurate and electronic structure of thallium chalcogenides

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.