Linear viscoelasticity in aluminum thin films

We have found that thin aluminum films at room temperature exhibit changes in elastic modulus of 25% or more over periods of an hour under stress by using a novel capacitance bulge system. Furthermore, we have strong evidence that this change is due to linear viscoelasticity. Such large changes in modulus can affect the stability and performance of microelectromechanical systems structures and need to be understood and controlled. These results are also proof that linear viscoelastic analysis is as appropriate for thin metal films as it is for many polymer systems. (c) 2005 American Institute of Physics.