Optical modification and metal complexation of ultrathin spin-coated polymer films

We report the successful metal salt complexation of ultrathin terpolymer films spin-coated onto glass and silicon substrates and the subsequent reduction of the salt to metal clusters. The photolabile polymer consists of a diazosulfonate side chain polymer which may be decomposed under UV irradiation. Initial, complexed and reduced stages are characterized using optical transmission spectroscopy and X-ray photoelectron spectroscopy, while the film surface roughness, morphology and thickness are determined from atomic force microscopy and ellipsometry. On the one hand, our experiments show that nonirradiated diazosulfonate side groups complex with silver acetate provided from solution, and that silver ions chemically reduce when exposed to a sodium borohydride solution. On the other hand, the complete destruction of the photolabile diazosulfonate unit with UV irradiation was proven. Our experimental investigations are the first successful effort for selective metallization of deposited ultrathin diazosulfonate polymer films. Furthermore, we were able to show that the films can be optically structured by writing micrometer-sized patterns with a focused UV laser beam.