Oberflächenpassivierung

Oberflächenpassivation, or surface passivation, is the process of creating or preserving a passive, protective surface layer to reduce chemical activity and guard against degradation. The aim is to minimize corrosion, oxidation, adsorption of contaminants, and the formation of electronic surface states that trap charge carriers. In German technical usage, the term is often Oberflächenpassivierung.

Common approaches include chemical passivation, such as acid treatments that form stable oxide layers on metals (for example stainless steel), thermal oxidation to grow oxide films, and the deposition of thin protective layers such as silicon dioxide, silicon nitride, aluminum oxide, or polymer coatings. Self-assembled monolayers using silanes or phosphonates provide molecular-scale passivation for various substrates.

In semiconductor and photovoltaic applications, passivation reduces surface recombination by saturating dangling bonds at silicon surfaces, frequently using Al2O3 or SiO2/Si3N4 stacks. In metals, protective oxide films mitigate corrosion and hydrogen embrittlement, while in polymers surface treatments can improve chemical resistance or biocompatibility.

Evaluation of passivation performance uses metrics such as corrosion rate, minority carrier lifetime or surface recombination velocity, and electrical contact resistance. Surface chemistry is characterized by techniques such as X-ray photoelectron spectroscopy, infrared spectroscopy, and ellipsometry.

Limitations include added layer thickness that may affect optical or electrical properties, potential delamination, and stability under thermal cycling or aggressive environments. The choice of method depends on the substrate, environment, and desired lifetime.