Perylene tetracarboxylic diimide ultrathin film deposition on Pt(1 0 0): a LEED, AES, REELS and STM study

We have investigated the first stages of organic molecular-beam deposition at room temperature of perylene-3,4,9,10-tetracarboxylic diimide (PTCDI) ultrathin films on Pt(1 0 0) by means of various techniques: Auger electron spectroscopy (AES), low energy electron diffraction (LEED), reflection electron energy loss spectroscopy (REELS) and ultrahigh vacuum (UHV) scanning tunneling microscopy (STM). w mainly that PTCDI grows on Pt(1 0 0) in the Stranski–Krastanov mode (as it is the case for perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) on Cu(1 1 0)). After the formation of a disordered first monolayer (ML), the formation of growing 3D crystalline islands of PTCDI was observed. Contrary to PTCDA deposited on Cu(1 1 0), annealing of the sample after deposition of the first monolayer did not lead to any molecular ordering. This could be due to a strong perpendicular interaction between platinum and adsorbed PTCDI molecules compared to molecular lateral ones. The EELS surface gap continuously opens to reach a value of 1.8 ± 0.2 eV for a deposit with an equivalent thickness of 20 ML, to be compared with 2.2 eV the expected highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap of PTCDI.