Growth of the TI GaSe2(1-x)S2x semi conductor crystals and to studied change of the band gaps energies as a function temperature

SUMMARY TlGaSe2(i-X)S2x single crystals were grown by the Bridgman-Stockbarger method. The absorption measurements were performed in TlGaSe2(i-X)S2x (TlGaSe2, x=0.2, x=0.4, x=0.6, x=0.8 and TlGaS2) samples in the temperature range 10-320 K. The direct and indirect energy band gaps were studied as a function of the temperature. The measurements were performed with steps of 20 K where the changes were small, and with steps of 5 and 10 K where the changes were large in the direct and indirect band gaps energies. The direct band gaps of TlGaSe2(i.x>S2X are 2.294 eV, 2.398 eV, 2.445 eV, 2.463 eV, 2.531 eV, 2.547 eV and the indirect band gaps are 2.148 eV, 2.252 eV, 2.305 eV, 2.432 eV, 2.442 eV and 2.501 eV, at 10 K, respectively. The phonon energies calculated for TlGaSe2(i-X)S2X (TlGaSe2, x=0.2, x=0.4, x=0.6, x=0.8, and TlGaS2) are 0.039 eV, 0,051 eV, 0.021 eV, 0.006 eV, 0.006 eV and 0.009 eV, respectively. The abrupt changes were observed in the direct and indirect band gaps at temperatures 90-100 K, 100 K, 100-120 K, 160-180 K, 220-240 K and 240-250 K. These changes were interpreted as phase transformation temperatures.