Temperature dependence of absorption edge anisotropy in 2H- MoSe2 layered semiconductors

The absorption-edge anisotropy of 2H- MoSe2 was studied by photoconductivity (PC) measurements as a function of temperature in the range of 12–300 K. A significant shift towards lower energies has been observed in the PC spectra on the edge plane with respect to those corresponding to the van der Waals (VdW) plane. The parameters that describe the temperature dependence of the absorption edges are evaluated by the Bose–Einstein empirical expression. Effective phonon energy was estimated from the temperature dependence of the Urbach energy. The estimated effective phonon energy for the VdW and edge planes, respectively, can be correlated to the observed Raman active E1g and A1g modes.