Postdeposition UV-Ozone Treatment: An Enabling Technique to Enhance the Direct Adhesion of Gold Thin Films to Oxidized Silicon

We found that continuous films of gold (Au) on oxidized silicon (SiO₂) substrates, upon treatment with ultraviolet (UV)-ozone, exhibit strong adhesion to the SiO₂ support. Importantly, the enhancement is independent of micro- or nanostructuring of such nanometer-thick films. Deposition of a second Au layer on top of the pretreated Au layer makes the adhesion stable for at least 5 months in environmental air. Using this treatment method enables us to large-scale fabricate various SiO₂-supported Au structures at various thicknesses with dimensions spanning from a few hundreds of nanometers to a few micrometers, without the use of additional adhesion layers. We explain the observed adhesion improvement as polarization-induced increased strength of Au^δ-Si^δ+ bonds at the Au-SiO₂ interface due to the formation of a gold oxide monolayer on the Au surface by the UV-ozone treatment. Our simple and enabling method thus provides opportunities for patterning Au micro/nanostructures on SiO₂ substrates without an intermediate metallic adhesion layer, which is critical for biosensing and nanophotonic applications.