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Ellipsometric study of electronic excitations in triglycine sulphate and triglycine selenate crystals
Author(s) -
Andriyevsky Bohdan,
Patryn Aleksy,
Cobet Christoph,
Mytsyk Bogdan,
Esser Norbert
Publication year - 2009
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200844384
Subject(s) - ferroelectricity , selenate , phase transition , dielectric , materials science , atmospheric temperature range , phase (matter) , analytical chemistry (journal) , ellipsometry , synchrotron radiation , triglycine sulfate , chemistry , nuclear magnetic resonance , condensed matter physics , optics , selenium , optoelectronics , physics , thin film , organic chemistry , chromatography , meteorology , metallurgy , nanotechnology
Abstract The real and imaginary parts of the pseudo‐dielectric susceptibility, 〈 χ 1 〉( E ) and 〈 χ 2 〉( E ), of triglycine sulphate (TGS) and triglycine selenate (TGSe) ferroelectric crystals have been obtained in the range 4–9.8 eV by spectroscopic ellipsometry using the Berlin Electron Storage Ring for synchrotron radiation source. A first maximum in 〈 χ 2 〉( E ) was found at E = 7.3 eV for both crystals and is attributed to the excitation of p‐electrons of oxygen. The spectra were measured at different temperatures in the range comprising the ferroelectric phase transition temperatures, 49 °C (TGS) and 22 °C (TGSe). Of note is the peak‐like behaviour in 〈 χ 1 〉( T ) and 〈 χ 2 〉( T ) near the phase transition temperature and a considerable decrease (about 50%) of the reflected light intensity I R in the range below the phase transition temperature ( T < T C ). The latter is probably caused by light scattering on the ferroelectric domain walls.