Spectroscopic ellipsometry study of above-band gap optical constants of layered structured TlGaSe2, TlGaS2 and TlInS2 single crystals

IŞIK M., Gasanly N., TURAN R.

PHYSICA B-CONDENSED MATTER, cilt.407, sa.21, ss.4193-4197, 2012 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 407 Sayı: 21
  • Basım Tarihi: 2012
  • Doi Numarası: 10.1016/j.physb.2012.07.003
  • Dergi Adı: PHYSICA B-CONDENSED MATTER
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.4193-4197
  • Anahtar Kelimeler: Semiconductors, Ellipsometry, Pseudorefractive index, OSCILLATOR PARAMETERS, ELECTRICAL-PROPERTIES, MIXED-CRYSTALS, TRANSITIONS, ABSORPTION
  • Orta Doğu Teknik Üniversitesi Adresli: Evet

Özet

Spectroscopic ellipsometry measurements on TlGaSe2, TlGaS2 and TlInS2 layered crystals were carried out on the layer-plane (0 0 1) surfaces, which are perpendicular to the optic axis c*, in the 1.2- 6.2 eV spectral range at room temperature. The real and imaginary parts of the pseudodielectric function as well as pseudorefractive index and pseudoextinction coefficient were found as a result of analysis of ellipsometric data. The structures of critical points in the above-band gap energy range have been characterized from the second derivative spectra of the pseudodielectric function. The analysis revealed four, five and three interband transition structures with critical point energies 2.75, 3.13, 3.72 and 4.45 eV (TlGaSe2), 3.03, 3.24, 3.53, 4.20 and 4.83eV (TlGaS2), and 3.50, 3.85 and 4.50 eV (TlInS2). For TlGaSe2 crystals, the determined critical point energies were assigned tentatively to interband transitions using the available electronic energy band structure. (c) 2012 Elsevier B.V. All rights reserved.