Materials by design—exploiting the unique properties of pulsed laser deposition for the synthesis of novel hard materials and structures

Novel multilayer thin film structures with an (A–B–C–B) four-sublayer periodicity were synthesized using pulsed reactive crossed-beam laser ablation. The layers were based on transition metal carbonitrides in which one sublayer (A=TiCxN1−x) was optimized for its high hardness, another (C=ZrCxN1−x) for its low frictional properties, and a third (B=VCxN1−x) which acted as a barrier to dislocation propagation. Control of growth and stoichiometry was facilitated by using thermally stable gases as sources for the carbon and nitrogen which were activated by collisions with the ablation plasma. It was discovered that the ablation yields of Ti, V, and Zr were almost identical, so that the sublayer thickness was directly proportional to the number of ablated shots per sublayer metal. The four-sublayer structures were harder (H̄=35 GPa) than corresponding bilayer structures (H̄=30 GPa) in which the VCxN1−x sublayers were missing. Further improvements are expected by optimizing the sublayer ratios and the absolute period thickness.