the structure and mechanical properties of superlattices have been studied since the 1960's.[1] The term "superlattice" in this case refers to any thin-film structure with a periodic composition modulation in the film growth direction.Superlattices are characterized by the distance between successive pair of layers,A,known as the 'bilayer repeat period'.In early work,Hilliard and co-workers used superlattices such as Ag/Cu for interdiffusion studies,where the nm-scale thicknesses allowed measurement of relative small diffusion coefficients.Early work also showed unusually large hardnesses in metallic superlattices.Interest in superlattice mechanical properties blossomed in the late 1970's,with the first report of the so-called supermodulus effect - an anomalously large (2-5 times) enhancement in elastic moduli for small composition-modulation periods #LAMBDA# approx2nm.however,most recent reports show only minor (approx approx 10
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