Mechanical behaviour of amorphous W–Si–N sputtered films after thermal annealing at increasing temperatures

Coatings containing tungsten, silicon and nitrogen (of three different compositions) were deposited by reactive sputtering from a tungsten target, which was embedded with silicon plates. Increasing partial pressures of nitrogen were used. All the coatings had an as-deposited amorphous structure. These were then subjected to thermal annealing treatment at increasing temperatures. The film with the lowest nitrogen content (W41Si41N18) crystallised as W5Si3 at an annealing temperature of 750°C; whereas for the other two coatings, W31Si36N33 and W26Si28N46, crystallisation took place at 950°C. In these two cases W5Si3 and α-W phases were detected. The hardness of the films increased after thermal annealing, reaching values as high as 45 GPa in films with a high nitrogen content.