The low-energy absorption edge in 2H-MoS2and 2H-MoSe2

Abstract

The optical transmission of thick samples of 2H-MoS₂ and 2H-MoSe₂ has been measured below the A exciton energy for each material. The absorption coefficients have been calculated, and the low absorption starting at 1·1–1·2 eV has been attributed to an indirect d-d transition for both materials. There appears to be considerable d-p valence band overlap giving rise to further higher absorption before the strong A, B excitons, which have been associated with direct transitions from a p-like valence band. An energy band scheme has been sketched on the basis of these interpretations.