Effect of negative bias voltage on microstructure and thermal stability of Cu/Nb nano-multilayers deposited by FCVA technique

he deposition energy is a crucial factor in the preparation of nano-metallic multilayers using the physical vapor deposition method. To study the effect of deposition energy on the microstructure and performance of coatings, Cu/Nb nano-multilayers were prepared by the FCVA technique with different negative bias voltages. The surface morphology, composition, and interface structure were investigated by SEM, XRD, and TEM. The results indicated that the increased negative bias voltage leads to compressive stress and the temperature rise effect, which promotes the formation of psedo-diffuse transition zones and the transformation of columnar to equiaxed crystals. In addition, the difference in hardness is used to characterize the structural integrity of the laminate structure of the material after heat treatment. Even after one hour of annealing at 600 °C, the sample retains a highly stable laminate structure when the negative bias voltage is set to -100 V, and its hardness reduces by just 22.3%. The mechanisms of the pseudo-diffuse transition zone and crystal structure on thermal stability were discussed.