Molecular-Scale Investigation of the Thermal and Chemical Stability of Monolayer PTCDA on Cu(111) and Cu(110).

Perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) has been intensively investigated for decades because of its unique electronic and optical properties and its applications in organic electronics and surface engineering and passivation of 2D materials. Recently, the high demand for achieving selective area deposition in device fabrications drives the research of utilizing organic molecules as a passivation layer on metals in the semiconductor industry. PTCDA molecules show promising potential to be used as a passivation layer on a metal surface because of their ability to form self-assembled compact lying-down layers with the well-exposed inert conjugated molecular π-plane. However, the thermal and chemical stabilities of monolayer PTCDA on metal surfaces have not been thoroughly studied. In this paper, we demonstrate that monolayer PTCDA on Cu(110) and Cu(111) surfaces exhibit good thermal and chemical stabilities, as revealed through the combination of in situ X-ray photoelectron spectroscopy and in situ low-temperature scanning tunneling microscopy measurements. We show that monolayer PTCDA on copper is stable up to 220 °C and decomposes to perylene at higher temperature. Monolayer PTCDA also shows good chemical stability when exposed to O ₂ and water, demonstrating good potential for its future applications as passivation layers in selective area deposition.