Coating dielectric substrates by plasma-reduction of metallic ions in solvents

We demonstrate herein the coating of dielectric surfaces with metallic thin films using the plasma-reduction of metallic ions such as HAuCl4, AgNO3, H2PtCl6, PdCl2, Ni(NO3)2 and Co(NO3)2 in solutions. Stable plasma was formed using 12 MHz/18 W and 2.45 GHz/900 W plasma generators and was confined in a Pyrex vacuum chamber with an inert gas environment. Depending on the controlled parameters, the fabricated films are either continuous or granular with grains of nano-size dimensions. All samples were chemically analyzed using X-ray diffraction analysis, and were morphologically observed using High Resolution Electron Beam microscopy. As an example of their electrical conductivity, Van der Pauw resistivity measurements were carried out for a gold layer at a wide temperature range. The smooth resistivity signal spreading at this range indicates that the conductive layer is stable and electrically continuous. An estimation of the adhesion of the deposited films was conducted by resistance measurements, followed by an ultrasonic bath treatment. Our results indicate no change in the resistance after this treatment, namely, a good adhesion of metallic particles to the glass surface has been achieved. The fact that this method is fast, simple, and low in cost (compared to other methods like sputtering or cvd), and can be applied for coating flat, rough, and porous surfaces can indicate its importance in future applications.