Disclosed herein are systems, methods, and apparatus for forming a low emissivity panel. In various embodiments, a partially fabricated panel may be provided. The partially fabricated panel may include a substrate, a reflective layer formed over the substrate, and a top dielectric layer formed over the reflective layer such that the reflective layer is formed between the substrate and the top dielectric layer. The top dielectric layer may include tin having an oxidation state of +4. An interface layer may be formed over the top dielectric layer. A top diffusion layer may be formed over the interface layer. The top diffusion layer may be formed in a nitrogen plasma environment. The interface layer may substantially prevent nitrogen from the nitrogen plasma environment from reaching the top dielectric layer and changing the oxidation state of tin included in the top dielectric layer.