Bimorphic, compositionally-graded, sputter-deposited, thin film shape memory device

Abstract

The present invention discloses devices and a method of fabrication of devices using a shape memory effect, thin film with a compositional gradient through the thickness of the film. Specifically, a NiTi SME thin film is disclosed that can be used in actuators, MEMS devices and flow control. The process of fabrication includes a gradual heating of the target over time during the sputter deposition of a thin film on a substrate under high vacuum, without compositional modification. The resulting thin film exhibits two-way shape memory effect that can be cyclically applied without an external bias force.

What is claimed is:  
     
         1 . A sputter deposition process for fabricating a thin film shape memory effect device, comprising: 
 inserting a Ni:Ti target and a substrate in an ultra high vacuum, sputter deposition chamber;    drawing an ultra high vacuum in the system, wherein the partial pressures of water, carbon dioxide and carbon monoxide are less than about 10 −8  Torr;    controlling the temperature of the target;    exposing the substrate;    depositing material from the Ni:Ti target to the substrate, wherein the temperature of the target is gradually increased over time.    
     
     
         2 . A sputter-deposited, thin film shape memory effect device, comprising a thin film of NiTi material, wherein the thin film of NiTi material is sputter deposited and wherein the thin film of NiTi has a compositional gradation through the thickness of the film, and wherein the compositional gradation is selected such that a phase change occurs above room temperature that activates a two-way shape memory effect.