Coherent growth and superhardness effect of AlN/TiN nanomultilayers

• Published in: Materials letters 2004-11, Vol.58 (27), p.3477-3480
• Main Authors: Mei, F.H., Shao, N., Dai, J.W., Li, G.Y.
• Format: Article
• Language: English
• Subjects: AlN/TiN nanomultilayers; Coherent growth; Cubic AlN; Superhardness effect
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2004.07.005

The formation of metastable cubic AlN (c-AlN) and its effect on the mechanical properties of AlN/TiN nanomultilayers were studied. A series of AlN/TiN multilayers with different modulation periods were prepared by reactive magnetron sputtering. The microstructure and mechanical properties of multilayers were characterized with low-angle X-ray diffraction, transmission electron microscopy and a microhardness tester. The results show that AlN exists as a metastable cubic phase in multilayers at small modulation periods due to the “template effect” of TiN layer and forms superlattice with TiN through coherent epitaxial growth. Correspondingly, multilayers show the superhardness effect with the enhancement of hardness at small modulation periods. With the increase of modulation periods, AlN layer grows as c-AlN firstly and then its stable hexagonal structure (h-AlN) appears and grows on the already formed c-AlN. Correspondingly, the hardnesses of the multilayers decrease. The change of properties with the formation of c-AlN and the alternative strain field resulting from coherent growth of c-AlN and TiN are likely reasons for the superhardness effect of AlN/TiN multilayers.