Layer Growth, Thermal Stability, and Desorption Behavior of Hexaaza-triphenylene-hexacarbonitrile on Ag(111)

Abstract

The layer growth, thermal stability, and desorption kinetics of ultrahigh vacuum (UHV)-grown organic discoid molecules (hexaaza-triphenylene-hexacarbonitrile (HATCN)) on Ag(111) have been studied by atomic force microscopy (AFM), thermal desorption spectroscopy (TDS), low-energy electron diffraction (LEED), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In the initial growth stage (≤0.24 nm mean film thickness) a strongly bonded monolayer of face-on oriented molecules is formed which does not desorb upon heating to 900 K, probably due to the formation of paracyanogen. With increasing film thickness the monolayer of face-on oriented molecules transforms at room temperature into a monolayer built up of edge-on oriented molecules, which saturates at a mean film thickness of around 0.8 nm. This layer partially decomposes during heating, and C2N2 fragments desorb between 650 and 900 K. On the monolayer of standing molecules a second, metastable, layer forms, which saturates at 1.36 nm. Wi...