ULTRAFAST ELECTRON DYNAMICS IN 2-DIMENSIONAL LAYERED SYSTEMS - 2-PHOTON PHOTOEMISSION-STUDIES OF SNS2

We performed femtosecond two-photon photoemission studies of SnS2, and measured the lifetime of electrons in the conduction band at differen t excitation energies. The lifetime is short (less than or equal to 60 fs) even at the conduction band minimum. In addition, the inverse lif etime shows a linear energy dependence. The experimental results are i nterpreted as due to the electron-plasmon interaction in layered two d imensional materials, which causes electron-hole recombination through the emission of a plasmon. These results are discussed in the context of the electron dephasing processes involved in the barrier crossing dynamics for electron transfer from physisorbed molecular donors at se miconductor surfaces (dye sensitization) under barrierless conditions. (C) 1997 Elsevier Science B.V.