Adsorption of α-pyridone on Cu(110)

Abstract

α-pyridone was absorbed onto a Cu(110) surface at room temperature under UHV conditions. This caused the (1×1) LEED pattern to fade suggesting adsorption into a disordered structure. Upon annealing to 590 K, an (8×2)gg LEED pattern with glide planes along both 〈110〉 and 〈001〉 directions was observed, which indicates the formation of a well-ordered monolayer. Following low-temperature (150 K) adsorption, temperature programmed desorption revealed the existence of a multilayer with a desorption temperature of 310 K, followed by desorption of the monolayer only above 850 K. High-resolution electron-energy loss spectroscopy showed that, initially in the monolayer at room temperature, the molecules have an upright geometry. However, annealing leaves only the out-of-plane CH bending mode at about 804 cm−1 which suggests that the molecule exclusively lies flat on the surface when the (8×2)gg periodicity is formed. Scanning tunneling microscopy reveals molecular resolution images of well-ordered monolayers. The experimental results are consistent with a model in which molecular dimers, held together by H-bonding, are the basic unit of the two-dimensional array.