SURFACE LATTICE-DYNAMICS OF KBR EPITAXIALLY GROWN ON RBCL(001)

High resolution He atom scattering experiments were performed on epita xially grown layers of KBr on a RbCl(001) substrate for coverages of o ne, two, and three monolayers. The in situ growth of the KBr was monit ored by following the intensity of the specularly scattered He beam ve rsus coverage. The inelastic scattering was measured for each deposite d layer to determine the surface phonon dispersion curves as a functio n of coverage in both the <(Gamma M)over bar> and <(Gamma X)over bar> high symmetry directions of the surface Brillouin zone. Fits to the da ta from the KBr/RbCl system, which is nearly perfectly lattice matched , were obtained from a shell model calculation whose parameters are fo und to provide not only a good match to the measured dynamics of these deposited films, but in addition, to the dispersion of bulk and clean surfaces of KBr, RbCl, KCl, and RbBr.