Adsorbed states of K on the diamond (100)(2×1) surface

Abstract

Abstract The adsorbed states of K on the C(100)(2×1) surface have been studied by electron energy loss spectroscopy (EELS), work function change (Δφ) measurement and thermal desorption spectroscopy (TDS). In the region where the K coverage is less than one-half of a monolayer (θ K ≤0.5), a loss is observed from ∼1.2 eV (θ K =0.2) to 1.0 eV (θ K =0.5); the work function decreases upon K adsorption until reaching a shallow minimum of Δφ=−3.35 eV at θ K =∼0.5; and a desorption peak (β) is observed from ∼825 K (θ K =0.05) to 525 K (θ K =0.5). These results indicate that the K–substrate bond is highly polarized; the 1.2 eV loss is attributed to the electronic transition from the bonding to antibonding states formed at the K–substrate interface. In the region between θ K =0.5 and 1, two losses are observed at 0.7 and 1.4 eV (θ K =0.6); there is only a small increase of the work function; and a desorption peak (α) is observed in addition to the β peak. These results indicate that the K regains its electron and becomes, essentially, neutral. The 1.4-eV loss is ascribed to the transition from the 4s to 4p states of K. The origin of the 0.7-eV loss is discussed. The Δφ and TDS results are analyzed by the depolarization model.