Abstract: The growth condition of mestable cubic AlN(c-AlN) in AlN/VN nanomultilayers and its effect on the mechanical properties of multilayers are investigated. A series of AlN/VN multilayers with different modulation periods are prepared by reactive magnetron sputtering technique. The microstructure and me-chanical properties of multilayers are characterized by low-angle X-ray diffraction, high-resolution transmission electron microscopy and a nanoindentor. The results show that AlN exists as mestable cubic phase (c-AlN) at small modulation period due to the “template effect”, and formed superlattice columnar srystal with VN through coherent epitaxial growth. Correspondingly, nanomultilayers show the superhardness effect with the enhancement of hardness and elastic modulus. With the increase of modulation period, c-AlN transformed to stable hexagonal structure (h-AlN) and multilayers form “brick-wall” structure with nanometer grains. The hardness and elastic modulus of multilayers are close to the value calculated from rule of mixture at large modulation period. The change of properties with the formation of c-AlN and alternative strain field resulted from coherent growth of c-AlN and VN appear to be one likely reason for the superhardness effect of AlN/VN nanomultilayers.

Key words: AlN, AlN/VN nanomultilayers, Mestable phasecubic, Superhardness effect