Abstract

The maybe superconductive and optobistable 2H MoS₂ compound was first studied by a photoacoustic spectroscopic method at room temperature. Our PAS measurements were performed on a conventional PAS set with particular protection against thermal and vibrational disturbances. The incident light from a 250-W sodium lamp through a monochromator fell on the MoS₂ cleavage surface of an ~50-μm thick sample, which was stuck to a piezoelectric ceramic sensor, in the measuring wavelength range from 540 to 740 nm at room temperature. We obtained three strong peaks at the absorption edge, namely, 595 nm (2.084 eV), 648 nm (1.913 eV), and 680 nm (1.823 eV), which agree well with respect to their positions and shapes with that obtained by Frindt and Yoffe¹ at 77 K by an ordinary method. We verified these results further on electrolyte electromodulation spectra and photomodulation reflectance measurements. These two peaks at 595 and 648 nm can be identified by calculating the absorption spectrum by the well-known transmission formula T = (1 – R)exp(–al) or by, more formally, Fermi’s golden rule through Loudon’s scattering matrix elements from the band structure of 2H-MoS₂ schemed in the paper of Evans and Young.² The peak appearing at 680 nm is probably due to the impurity activities.

© 1988 Optical Society of America