Low-fluence laser induced fragmentation and desorption of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) thin film

摘要

Laser-induced fragmentation and desorption of fragments of PTCDA films vacuum-deposited on GaAs(l00) 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 C_(20)H_8, its half C_(10)H_4, carbon dioxide, carbon monoxide and atomic oxygen. All desorbing fragments have essentially different kinetic energy. The mechanism of photomduced molecular fragmentation and desorption is discussed.