XPS and electronic structure of ferroelectric Sn₂P₂S₆crystals

Abstract

Electronic properties of uniaxial ferroelectric Sn2P2S6 single crystal are studied by X-ray photoelectron spectroscopy. X-ray photoelectron spectra (XPS) of the valence band (VB) and of the principal core levels (CL) are obtained from different crystallographic planes in both paraelectric and ferroelectric phases. The XPS were measured with monochromatized Al Ka radiation in the energy range 0-1400 eV. The VB consists of five bands with the maxima between 3.3 and 14.5 eV below the Fermi level. Experimental energies of the VB and core levels are compared with results of theoretical ab initio calculations of molecular model of the Sn2P2S6 crystal. Electronic structure of the VB is revealed. Ferroelectric phase transition changes atom's charge and bonds strength, VB electronic structure, CL lines width, and chemical shifts for the Sn, P, and S states which are crystallographic plane-dependent.

Fabrication of Novel 3-D Nanocomposites of HAp–TiC–h-BN–ZrO2: Enhanced Mechanical Performances and In Vivo Toxicity Study for Biomedical Applications

“…The Ca 2p’s high-resolution (HR) XPS spectra (Figure b) showed two peaks with binding energies (BEs) of 349.04 and 345.28 eV, which were caused by the spin states of 2p 1/2 and 2p 3/2 . Further, the deconvoluted spectra of phosphorus (P) 2p (Figure c) noticed at BEs of 136.73 and 131.5 eV are due to the spin–orbit splitting state of 2p 1/2 from the phosphate group (PO 4 3– ) of HAp and TCP, , while the deconvoluted O 1s spectra (Figure d) at 531.04 and 529.25 eV are ascribed to Zr–O–Zr and Zr–O Figure e shows a deconvoluted XPS spectrum of B 1s, containing three peaks at different BEs of 190.02, 188.81, and 188.52 eV, ascribed to the B–N, B–O, and B–B bonds, respectively. , Figure f shows the HR-XPS spectrum of N 1s, which contains two peaks at 401.85 and 398.3 eV, attributed to the N–O and N–B bonds. , The Zr–O bond of calzirtite was ascribed to the fitted peaks over the Zr 3d spectrum (Figure g) of the components 3d 3/2 at 183.7 eV and 3d 5/2 at 181.38 eV .…”

Development of Bi2S3/Cu2S hetrojuction as an effective photocatalysts for the efficient degradation of antibiotic drug and organic dye

“…The observed carbon peak at 285.1 eV for binding energy is ascribed to carbon present in grid used for XPS analysis. The S 2p region is defined by two asymmetric peaks, S 2p 3/2 is responsible for the highest intensity peak approximately at 165 eV and the spin state of S 2p 1/2 is responsible for the small peak at 159.8 eV (Grigas et al 2008 ). Cu 2p1/2 and 2p3/2 binding energies were evaluated to be 956.53 and 936.46 eV, respectively (Hassanien et al 2016 ), representing the presence of copper in the active catalysts.…”

“…5. Bi 4f 7/2 and Bi 4f 5/2 emerge at 160 is responsible for the small peak at 159.8 eV (Grigas et al 2008). Cu 2p1/2 and 2p3/2 binding energies were evaluated to be 956.53 and 936.46 eV, respectively (Hassanien et al 2016), representing the presence of copper in the active catalysts.…”

Annealing-induced formation of Sn2P2S6 crystallites in As2S3-based glass matrix

“…At ambient pressure, the Sn 2 P 2 S 6 crystal undergoes a second-order structural transition from the ferroelectric phase (Pn) to the paraelectric (P2 1 /n) one at 337 K, which was thoroughly investigated by X-ray diffraction [5], dielectric studies [6], Raman scattering [7][8][9], inelastic neutron scattering [10], ultrasonic measurements [11], optical spectroscopy [12], birefringence measurements [13], Mössbauer spectroscopy [14,15], X-ray photoelectron spectroscopy [16,17], soft X-ray fluorescence spectroscopy [16], and thermal expansion studies [18]. In most cases, these studies were carried out for good quality bulk single crystals.…”