Effect of the thermal annealing on the properties of RF sputtered Mo-AlNxOy composite thin films

• It was studied the effect of annealing temperature on the Mo-AlNxOy films.
• Annealing promotes absorptance increase and morphology change.
• Annealing at 600 °C did not alter properties of the films.
• This material can be used in selective surfaces.

In the last few years, the concentrating solar power (CSP) systems have been studied and growing surprisingly in several countries. The science and technology involved to manufacture the special materials for these devices has been a determining factor for the system performance. Among these special materials, ceramic-metal composite (cermet) is an important class largely used as a main absorber in the selective surfaces of evacuated tube collectors. This work aims to manufacture Mo-AlNxOy thin films by magnetron sputtering technique. The parameter studied was the effect of annealing temperature (600ºC-1100 °C) on the optical properties and surface morphology of the films. The results showed that the annealing (800-1100 °C) increase the absorptance, produces an oxidation in the bulk of the films and a breakage in the AlN surface bonds, reducing the initial quantity of nitrogen. It is noteworthy that the annealing at 600 °C did not alter the optical and morphology properties of the films, suggesting that the films of Mo-AlNxOy produced can be applied in selective surfaces in the future.