Adsorption and Growth of 1,3,5-Triazine on Cu(111) at Low Temperature under Ultrahigh Vacuum Conditions

Abstract

The self-assembly of 1,3,5-triazine molecules on Cu(111) surfaces is studied by means of variable-temperature scanning tunneling microscopy (VT-STM) at low temperature under ultrahigh vacuum (UHV) conditions. Depending on the substrate temperature during the exposure, three different phases have been found. At the highest temperature (210 K), and close to the desorption limit, a (3 × 3) phase, with one molecule per unit cell, is found. At lower temperature (around 170 K), two different phases, the herringbone and the “daisy” phases, with much higher molecular densities and larger unit cells are found. Structural models of each of these phases are proposed on the basis of high-resolution STM images. According to these models, the orientation of the molecular plane with respect to the Cu(111) surface is strongly dependent on the adsorption temperature and on the molecular density.