Relaxation and recovery of extrinsic stress in sputtered titanium-nickel thin films on (100)-Si

The relaxation and recovery of stresses by displacive phase transformations in near-equiatomic titanium-nickel thin films sputtered onto (100)-silicon have been studied using the wafer curvature method, X-ray diffraction and in-situ resistivity measurements in hard vacuum. Large extrinsic tensile st resses were relaxed and recovered by displacive transformations during cycl ic thermal excursions between M-f and A(f). More than 0.6 GPa could be rela xed by the R-phase transformation alone. Two-step B2 --> R --> B19' transfo rmations were often observed on cooling, but for Ti-rich compositions, reco very of extrinsic tensile stresses proceeded via a one-step B19'-->B2 trans formation, at stress-rates (d sigma/dT) as high as 60 MPa K-1. Stress-rates , and details of hysteretic behavior, are discussed in terms the distributi on of stress in multiphase intermediate (mid-transformation) microstructure s formed by alternative development modes. An approach is suggested for the control of hysteresis through the use of functional composition gradients. (C) 1999 Published by Elsevier Science S.A. All rights reserved.