Thin films formation of poly(N-vinylcarbazole) by laser ablation deposition

The laser-ablation deposition technique was examined for poly(N-vinylcarbazole), PVCz, which is a representative photoconductive aromatic vinylpolymer. Thin films were deposited under various irradiation conditions (laser wavelengths were 351, 308, and 248 nm and their fluences were 70, 300, and 450 mJ/cm²), and their chemical structures and surface morphology were revealed by means of infrared-absorption, fluorescence spectroscopy, and atomic force microscopy, respectively. They were quite sensitive to the laser fluence, as well as wavelength. A thin film of PVCz was formed only under an optimum irradiation condition where the laser fluence and wavelength were 300 mJ/cm² and 351 nm, respectively. When the irradiation condition deviated from the optimum one, thin films contained carbazolyl derivatives such as N-alkylcarbazole and N-vinylcarbazole oligomers. It was revealed that the thin PVCz film was formed by a repolymerization due to radical mechanism. In addition, it was suggested that cross-linking reactions occurred in the films deposited at 248 and 308 nm. All the films were amorphous, and particle-like aggregates, with sizes varying with the irradiation conditions, were observed on their surface. It was demonstrated that the ablation-deposition technique is applicable to the formation of thin PVCz films.