Optical Absorption of a Few Unit-Cell Layers of MoS2

Abstract

An experimental study of the absorption edge of single crystals of Mo${\mathrm{S}}_2$ down to a thickness of a few unit-cell layers has been carried out. With crystals less than 30 Å thick, the strong absorption peak in the red part of the spectrum disappears. Structure on the short-wavelength side of this peak disappears at a thickness of about 125 Å. These changes may be due to exciton size effects. The strength of a peak in the orange part of the spectrum is independent of thickness, down to the thickness of a few unit-cell layers. A new peak is observed with crystals less than 50 Å thick.