Potassium-induced reconstructive phase transitions on Au(100)

Abstract

The adsorption of potassium on the quasi-hexagonally reconstructed (“5 × 20”) Au(100) surface has been studied in the temperature range between 130 K and 300 K employing LEED, AES, XPS, and work function (Δф) measurements. At room temperature, an intermediate work function maximum is correlated with a transition of the quasi-hexagonal substrate surface into a (1 × 2) phase caused by a missing-row reconstruction of the Au(100) surface. The lifting of the quasi-hexagonal Au reconstruction is also accompanied by a sudden decrease of the potassium 2p32 core level binding energy by ∼ 0.9 eV. Further adsorption of potassium leads to the formation of complex LEED patterns (among others a c(4 × 4) phase) until the monolayer saturation is attained around Θ ≈ 0.38. Lowering the surface temperature to 130 K does not stabilize the clean surface reconstruction sufficiently to allow formation of stable potassium overlayer phases on the (“5 × 20”)-reconstructed Au(100) surface; instead Δф and LEED measurements at 130 K indicate disorder and partial inhibition of the transition into the reconstructed (1 × 2) phase pointing to a thermally activated process. All in all, we confirm results of a recent STM/LEED/AES study on the Au(100)K system and provide further evidence for the idea whereafter elevated potassium coverages may favor interlayer mixing and/or growth of a potassium—gold alloy.