Annealing effect on microstructure and mechanical properties of amorphous Al-C-N films

Al-C-N thin films with different Al contents were deposited on Si (1 0 0) substrates by closed-field unbalanced reactive magnetron sputtering in the mixture of argon and nitrogen gases. These films were subsequently vacuum-annealed at 700 °C and 1000 °C, respectively. The microstructures of as-deposited and annealed films were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM); while the hardness and elastic modulus values were measured by nano-indention method. The results indicated that the microstructure of both as-deposited and annealed Al-C-N films strongly depended on Al content. For thin films at low Al content, film delamination rather than crystallization occurred after the sample was annealed at 1000 °C. For thin films at high Al content, annealing led to the formation of AlN nanocrystallites, which produced nanocomposites of AlN embedded into amorphous matrices. Both the density and size of AlN nanocrystallites were found to decrease with increasing depth from the film surface. With increasing of annealing temperature, both hardness and elastic modulus values were decreased; this trend was decreased at high Al content. Annealing did not change elastic recovery property of Al-C-N thin films.

Research highlights► This study revealed that the microstructure of annealed Al-C-N films strongly depended on not only annealing temperature but also Al content. ► At a low temperature below 700 °C, Al-C-N shows its high thermal stability. ► When temperature was increased to 1000 °C and above, Al-C-N thin films with different Al contents exhibited different annealing responses. ► For the thin films at low Al content, film delamination rather than crystallization occurred. ► Otherwise, annealing treatment led to the formation of nanocomposites of AlN embedded into amorphous matrices.