Urbach's rule and steepness parameter of 2H-WSe2 layered crystals have been studied via the absorption spectra from the photoconductivity (PC) measurements in the temperature range of 15-300 K. From the analysis of the temperature-dependent band gap with Varshni semi-empirical equation, the Debye temperature was estimated as 160 K while the Einstein temperature was around 125 K from the Einstein oscillator model. The effective phonon energy was estimated successfully from the temperature dependence of the Urbach energy extracted from the PC spectra and the value was found out to be well correlated to the active E1g mode observed in the Raman spectra of 2H-WSe2.
Relation:
physica status solidi (a), Vol.204 no.7, pp. 2389-2395
