Provided is High Productivity Combinatorial (HPC) testing methodology of semiconductor substrates, each including multiple site isolated regions. The site isolated regions are used for testing different compositions and/or structures of barrier layers disposed over silver reflectors. The tested barrier layers may include all or at least two of nickel, chromium, titanium, and aluminum. In some embodiments, the barrier layers include oxygen. This combination allows using relative thin barrier layers (e.g., 5-30 Angstroms thick) that have high transparency yet provide sufficient protection to the silver reflector. The amount of nickel in a barrier layer may be 5-10% by weight, chromium—25-30%, titanium and aluminum—30%-35% each. The barrier layer may be co-sputtered in a reactive or inert-environment using one or more targets that include all four metals. An article may include multiple silver reflectors, each having its own barrier layer.