Copper Phthalocyanine (CuPc) thin films were deposited on the [100] single crystal silicon wafers by evaporation (e-CuPc) of the CuPc powders (monoclinic crystal) and in the Ar plasma (pe-CuPc). The structures of the e-CuPc and pe-CuPc thin films were analysed by means of IR spectroscopy, Raman spectroscopy, XPS, AES SEM, and TEM.
The main molecular structure of the CuPc, which is the conjugated aromatic heterocyclic ring structure, ws hardly altered by the Ar plasma. The carboxyl functional group at the peripherial bengene ring was identified by IR spectra and XPS. Organic impurities such as H2Pc were detected in the CuPc powders (Aldirch, β form, dye content 97%). which remained as impurities in the e-CuPc and pe-Cupc thin films. Oxygen impurities were not found in the e-CuPc thin films, but found in the pe-CuPc thin films. Neutral oxygen molecules trapped in the CuPc powders were pumped out during the evaporation process, while those were activated and interacted with the unknown organic impurities in the plasma which would come from CuPc powders and/or byproducts of plasma chemistry. The hydrogen bonding between on hydrogen in the carboxyl group and on bridge nitrogen of the CuPc molecule would prevent the Pe-CuPc thin film to have a crystalline structure. The amorphous structure of the pe-CuPc thin film was identified, by Raman spectroscopy and TEM. The morphologies of the e-CuPc and pe-CuPc thin films were greatly different. The e-CuPc thin film have the acicular crystllites which have grown in the perpendicular direction to the silicone substrate. The pe-CuPc thin films have granule-like morphology, which were similar irrelavant to the rf power variations.
