Crystallization of Amorphous and Superhardness Effect in Nano-multilayer Films

Template-induced epitaxial crystallization of SiC,TiB_2 and SiO_2 in TiN/SiC,TiN/TiB_2 and TiN/SiO_2 nano-multilayer films and its influence on mechanical properties of the correspond- ing films were investigated.Results reveal that amorphous SiC,TiB_2 and SiO_2,which are more favorable under sputtering conditions,crystallize at smaller layer thicknesses due to the template effect of c-TiN layers.In particular,SiC crystallizes out in the face-centered cubic structure when its thickness is less than 0.6nm,which improves the crystal quality and structural integrity of the films;While TiB_2,with thickness less than 2.9nm,forms hcp structure.The epitaxial orientation relationship between TiN and TiB_2 is {111}TiN//{0001}TiB_2,〈100〉TiN //〈11(?)0〉TiB_2;SiO_2, different from the above two,forms fcc pseudo-crystalline structure under a thickness of 0.9nm. With the crystallization of SiC,TiB_2 and SiO_2,hardness anomalous enhancement,i.e.superhard- hess effect,appears in those films.This phenomenon of hardness enhancement disappears rapidly when further increase the thickness of SiC,TiB_2 and SiO_2 layers,and at the same time,crystallines of SiC,TiB_2 and SiO_2 transform into their amorphous forms,respectively.The formation of these relatively soft amorphous layers,which blocks the coherent growth of the multilayer films,is the main reason of hardness decline at large SiC,TiB_2 and SiO_2 layer thicknesses.