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

Le-The, Hai; Tiggelaar, Roald M; Berenschot, Erwin; van den Berg, Albert; Tas, Niels; Eijkel, Jan C T · ACS Nano · 2019

basic_science · Level V

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Abstract

We found that continuous films of gold (Au) on oxidized silicon (SiO<sub>2</sub>) substrates, upon treatment with ultraviolet (UV)-ozone, exhibit strong adhesion to the SiO<sub>2</sub> 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 SiO<sub>2</sub>-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<sup>δ-</sup>Si<sup>δ+</sup> bonds at the Au-SiO<sub>2</sub> 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 SiO<sub>2</sub> substrates without an intermediate metallic adhesion layer, which is critical for biosensing and nanophotonic applications.