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Preparation and fundamental absorption edge of In4(P2Se6)3 single crystals

The methods of synthesis and growth of good quality, uniaxial In4(P2Se6)3 single crystals are worked out. The temperature dependence of the optical absorption edge of these crystals was studied at high absorption levels in the range of direct optical transitions. At low temperatures we have observed an exciton band corresponding to the optical absorption with the formation of direct s-excitons. In the long-wavelength spectral range the absorption edge Urbach tails are observed. We have shown that the exponential dependence of a on photon energy is a consequence of exciton-phonon interaction whose mechanism is explained within the framework of Dow-Redfield theory. The influence of disorder on the width of Urbach tails was analysed as well.

hyposelenophosphates; direct exciton absorption; Urbach tail; exciton-phonon interaction

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