EFFECTS OF THE LITHIUM INTERCALATION ON THE OPTICAL BAND-EDGE OF WS2

Effects of the lithium intercalation on the optical band edge of the l ayered dichalcogenide WS2 have been studied. Transmission spectra were made at low-temperature (T=5 K) on WS2 and LixWS2 single crystals. A red shift of the fundamental absorption edge and a screening of the ex citonic transitions were observed upon Li intercalation. The modificat ions of the optical properties are attributed both to a weak charge tr ansfer of electrons from intercalant species to the host matrix and to the destabilization of the electronic band structure due to the inter action between the 2s state of Li localized in the van der Waals gap w ith the (s,p) group of the host. Results show that the rigid-band mode l is clearly not applicable to this system. (C) 1998 Elsevier Science B.V. All rights reserved.