Perylene tetracarboxylic diimide ultrathin film deposition on Pt(100): a LEED, AES, REELS and STM study

Abstract 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). We show 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.