The Urbach tails and optical absorption in layered semiconductor TlGaSe2 and TlGaS2 single crystals

Gurbulak B., Duman S., Ates A.

CZECHOSLOVAK JOURNAL OF PHYSICS, cilt.55, sa.1, ss.93-103, 2005 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 55 Sayı: 1
  • Basım Tarihi: 2005
  • Doi Numarası: 10.1007/s10582-005-0011-4
  • Dergi Adı: CZECHOSLOVAK JOURNAL OF PHYSICS
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.93-103
  • Anahtar Kelimeler: single crystal, direct and indirect band gaps, Urbach energy, steepness parameters, PHASE-TRANSITIONS, SPECIAL FEATURES, TLINS2, PHOTOCONDUCTIVITY, SPECTRA, EDGE, PARAMETERS, GROWTH
  • Atatürk Üniversitesi Adresli: Evet

Özet

TlGaSe2 and TlGaS2 single crystals were grown by the modified Bridgman-Stockbarger method. We report the result of an experimental study of the optical absorption of TlGaSe2 and TlGaS2 crystals. The absorption measurements were performed in steps of 10 K. The direct and indirect band gaps for TlGaSe2 and TlGaS2 samples were calculated as a function of temperature. The phonon energies in TlGaSe2 and TlGaS2 crystals were calculated as (39 +/- 4) and (9 +/- 4) meV at 240 K, respectively. At 10 K, directand indirect band gaps were found as 2.294 and 2.148 eV for TlGaSe2, 2.547 and 2.521 eV for TlGaS2 crystals, respectively. The abrupt changes were observed in the direct and indirect band gaps in the some temperature ranges. These changes were interpreted as phase transformation temperatures. The steepness parameters and Urbach energy for TlGaSe2 and TlGaS2 samples increased with increasing sample temperature in the range (10-320) K.