ADSORPTION OF PYRIMIDINE MOLECULES ON PD(110) OBSERVED BY SCANNING-TUNNELING-MICROSCOPY

Adsorbed stales of pyrimidine molecules on Pd(110) have been studied b y a scanning tunneling microscope (STM), The pyrimidine molecules are preferentially adsorbed on terraces, not at steps. The isolated pyrimi dine molecule shows a 0.6 nm x 0.6 nm rectangular shape with two parts of elongated protrusions. Two adsorption sites are observed: on-top s ite of the Pd[1(1) over bar0$] row and the midway between two [1(1) ov er bar0$] rows, Pyrimidine molecules show a strong tendency to form di mers even at a low coverage (0,01 ML), indicating that there is an att ractive interaction between two adsorbed molecules.