Laser sintering of perovskite-oxide and metal coatings by the sol gel process

This paper presents a novel laser technique for the formation of metal Ag and perovskite-oxide La_xSr_1-xCoO₃ coatings. Metallic Ag and La_xSr_1-xCoO₃ are conductive materials with applications as resistors and as electrodes in the microelectronics area. Suitable precursors in the form of sol gels are placed on substrates and are subsequently sintered by high-power laser irradiation. The Ag precursor is an aqueous sol of nanosized particles, while for the La_0.8Sr_0.2CoO₃, a sol gel type precursor is used. Substrates (e.g., fused silica) are coated with the precursor solutions by spinning and are dried to stable solid layers. The coatings are cured and sintered to a defined pattern by means of a 3-kW CO₂ laser beam scanned over the whole substrate surface. The microstructure of the coatings was examined by the use of scanning electron microscopy and X-ray diffraction, and the electrical properties were measured by the four-point resistivity method. The La_0.8Sr_0.2CoO₃ coatings had a perovskite cubic structure with a lattice constant of 0.383 nm. The resistivity of the coatings was 30 mQ cm, and the temperature dependence of the resistivity was 1.8 mQ cm/°C. Metallic Ag coatings with a thickness of 100-170 nm were obtained with a resistivity of 20 7Q cm. This new technology is promising for the growth of three-dimensional (3-D) structures and multilayers, especially because it can be introduced in industrial scale production.