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Abstract
Ni–Ti thin films of various compositions were sputtered-deposited on silicon substrates. Their mechanical properties (hardness and Young's modulus) were then determined using a nanoindenter equipped with a Berkovich tip. This paper examines the effects of composition on the mechanical properties (hardness and Young's modulus) of the sputter deposited Ni–Ti thin films. This is of particular interest since the actuation properties of these shape memory alloy films are compositionally sensitive. The surface-induced deformation is revealed via Atomic Force Microscopy (AFM) images of the indented surfaces. Which show evidence of material pile-up that increases with increasing load. The measured Young's moduli are also shown to provide qualitative measures of the extent of stress-induced phase transformation in small volumes of Ni–Ti films.
ACKNOWLEDGMENTS
This research was supported by National Science Foundation (NSF) IMI Programs at Iowa State University (DMR 0231291) and Princeton University (DMR 0231418). The authors are grateful to IMI Program Manager Dr. Carmen Huber for her encouragement and support. Also, the film deposition worked at Yale University (Dr Ainissa Ramirez) was supported by the National Science Foundation (DMR 0347095).