LOW-FLUENCE LASER INDUCED FRAGMENTATION AND DESORPTION OF 3,4,9,10‐PERYLENETETRACARBOXYLIC DIANHYDRIDE (PTCDA) THIN FILM

Laser-induced fragmentation and desorption of fragments of PTCDA films vacuum-deposited on GaAs(100) substrate has been studied by time-of-flight (TOF) mass spectroscopy. The main effect caused by pulsed laser light irradiation (pulse duration: 10 ns, photon energy: 2.34 eV and laser fluence ranging from 0.5 to 7 mJ/cm2) is PTCDA molecular fragmentation and desorption of the fragments formed, whereas no desorption of intact PTCDA molecule was detected. Fragments formed are perylene core C20H8, its half C10H4, carbon dioxide, carbon monoxide and atomic oxygen. All desorbing fragments have essentially different kinetic energy. The mechanism of photoinduced molecular fragmentation and desorption is discussed.