Stability of a surface adlayer at elevated temperature: Coronene and heptanoic acid on Au(111)

The temperature dependence of the stability of the adlayer formed at the interface between Au(111) and a coronene-heptanoic acid solution is reported. At coronene concentrations above 1.5 x 10(-4) M and at 21 degrees C, a dense coronene adlayer is observed. At higher temperatures (up to about 60 degrees C) or in a more dilute solution, a coadsorbed coronene-heptanoic acid structure is observed. This coadsorbed structure is very hardy, surviving exposure to the pure solvent for periods of many minutes and temperatures as high as 105 degrees C. Loss of the ordered monolayer with high temperature solvent exposure is also accompanied by the formation of at least two additional surface structures involving both coronene and heptanoic acid. This work demonstrates that there is much to be learned by exploring the solution-solid interface at elevated temperatures with STM.