Silver is the de facto choice for the active layer in low-emissivity coatings used in energy-saving window applications. In its bulk state it is fully opaque, but it becomes optically transparent when very thin (~10 nm), while still preserving good electrical properties. Industrially, silver is typically synthesized from the vapor phase using magnetron sputtering. During vapor condensation on the substrate surface, high supersaturation at the vapor/solid interface leads to a far-from-equilibrium process, such that film growth is governed by a complex interplay between thermodynamics and kinetics. This interplay leads to a pronounced 3D film morphological evolution, which represents a roadblock for enabling the full potential of silver in low-emissivity coatings. Over the past 20 years, commercial actors have utilized a seed layer (e.g., zinc oxide) to grow silver upon, which promotes layer wettability, crystallographic texturing, and improved optoelectronic properties. However, ever since the seed layer advent, the industry has failed to reach a similar step change in silver layer improvement. Here, we present a novel concept for a new class of transparent conductive layers that is based on strategically introducing alloying agents to silver during its deposition. These agents modify the local atomic environment at the film growth front; this tunes the kinetic rates of atomic-scale processes that drive interlayer mass transport and formation of 3D nanostructures during silver nucleation, growth, and coalescence. The resulting silver film morphology yields superior optical and electrical properties; also, by inherently being an alloy, the mechanical and chemical properties are significantly improved.
Selective alloying of thin silver films: a strategy for next generation energy-saving windows
Company: MIMSI Materials AB, Linköping, Sweden / University of Helsinki, Helsinki, Finland
About the speaker:
Kostas Sarakinos is CSO at MIMSI Materials and Associate Professor at the Department of Physics at the University of Helsinki, Finland, He holds a Ph.D. degree in Physics from RWTH Aachen University, Germany (2008) and a Habilitation degree in Materials Science from Linköping University, Sweden (2012). Kostas’s research interests include atomistic processes during film nucleation and growth, growth manipulation, in situ growth monitoring, and deterministic and stochastic film growth simulations. He has (co)authored 70 papers and 4 book chapters, while he is (co)inventor in 8 patents.