Elastic properties of amorphous thin films studied using Rayleigh waves

Physical vapor deposition in an ultrahigh vacuum was used to codeposit nickel and zirconium onto quartz single crystals and grow amorphous Ni_1-xZr_x (0.1< x < 0.87) thin films. A high resolution surface acoustic wave technique was developed for the in situ measurement of the film shear moduli. The modulus has narrow maxima at x = 0.17, 0.22, 0.43, 0.5, 0.63 and 0.72, reflecting short-range ordering and the formation and aggregates in the amorphous phase. It is proposed that the aggregates correspond to polytetrahedral atom arrangements which are limited in size by geometrical "frustration".