Stability of organic thin films on inorganic substrates: prototype studies using metal phthalocyanines

Abstract

Thin films of metal phthalocyanines (PbPc and RuPc) on Inorganic substrates lAg. Pt. Cu, Au. Alz0 3 and Ag!) In the submonolayer and monolaye, range were Investigated. Their chemical compositions and electronic and dynamic structures were characterized by means of photoemission and vibrational spectroscopy, with particular emphasis on the influence of the filmJsubstrate and film/gas phase interfaces. The results Indicate that RuPc surfaces are always unstable In air because of an energetically favourable oxlda formation involving the central (Ru) atom. Lead phthalocyanina is more stable. lead oxides ere formed only after exposing thin films prepared under urtra-hlgh vacuum to pure oxygen. Even for PbPc. decomposition was observed at certain substrate/film Interfaces: orgenlc fragments were found In the submonolayer fange on platinum substrates. an exchange of the central atom on coppe, substrates and catalytic dacompositlon of organic films on gold substrateS aftar storaga in ai,. Chemically perfect films without decomposition were found on AI:z0 3 • Agi and Ag substrates. The results are discussed by taking Into account the energetic structure of Interfacial electronic states.