Roughening transition in adsorbed xenon multilayers

Abstract

Experimental evidence for a roughening transition in adsorbed xenon multilayers on palladium is presented. The clearly layer-distinctive Xe 5p photoemission is used to measure adsorption isotherms as well as the relative equilibrium population of individual Xe layers. Below a transition temperature TR xenon is adsorbed layer by layer—each layer being completed before any substantial population of the next layer occurs—with sharp first order phase transition steps for the second and third layer. Above TR the adsorption proceeds in a continuous manner, with rounded steps in the isotherms and simultaneous population of different layers. Layer population and critical temperature analysis suggests that the transition temperature is indeed the roughening temperature of the Xe film.