Adsorption of Li on C 60-covered Ni(1 1 0) surfaces

Abstract

In the present paper we study the adsorption of Li on C 60-covered Ni(1 1 0) surfaces by means of Auger electron spectroscopy, low-energy electron diffraction, thermal desorption spectroscopy and work function measurements, in ultrahigh vacuum. During Li deposition on 1 ML C 60/Ni(1 1 0) surfaces, a considerable amount of charge is transferred to the C 60 overlayer, leading to a partial or complete occupation of the t 1g-derived band of C 60. The above charge transfer delays the metallization of Li as compared to the clean Ni(1 1 0) surfaces and increases its binding to the Ni(1 1 0) substrate ( E b=1.72 eV/atom). The sticking coefficient of Li remains constant for high Li coverages ( Θ Li⩾7 MLs), due to its strong interaction with the C 60 overlayer. Charge transfer to the C 60 molecules and reduced metallic character of the Li overlayer is also observed during Li deposition on a (5×3)-C 60 on Ni(1 1 0), while, the presence of the (5×3) islands results in the appearance of Li structures formed in the bare regions of the Ni substrate. In both cases, the presence of C 60 prevents the Li-induced (1×2) reconstruction which is observed for Li deposition on clean Ni(1 1 0) surfaces.