Investigation of furan on vicinal Pd(1 1 1) by scanning tunneling microscopy

We have used scanning tunneling microscopy to image furan adsorbed on vicinal Pd(1 1 1) at temperatures below the onset of decomposition of the furan molecule. Studies conducted on two substrates with relatively narrow and wide terraces reveal strikingly different behaviors. Adsorbates on narrow vicinal planes are mobile at 225 K, while a scattered cluster distribution is observed on broader vicinal planes at comparable temperatures. Both surfaces exhibit upper step edges that are densely populated with furan molecules, which qualitatively match predicted STM images of furan generated from extended Hu¨ckel theory.