AVS 45th International Symposium
    Nanometer-scale Science and Technology Division Wednesday Sessions
       Session NS+AS-WeM

Paper NS+AS-WeM6
Nanoindentation as a Probe of Stress State

Wednesday, November 4, 1998, 10:00 am, Room 321/322/323

Session: Innovative Force, Near-Field Optics, and Tunneling Measurements
Presenter: K.F. Jarausch, North Carolina State University
Authors: K.F. Jarausch, North Carolina State University
J.D. Kiely, Sandia National Laboratories
J.E. Houston, Sandia National Laboratories
P.E. Russell, North Carolina State University
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A dependence of elastic response on the local stress-state of a material has been demonstrated using the interfacial force microscope (IFM). This investigation was prompted by a previous IFM survey in which the mechanical response of Au thin films was found to correlate with the films' residual stress state and not with morphology or substrate adhesion. In order to better establish the details of this relationship a concentric ring bending device was built to investigate the dependence of IFM nanoindentation measurements on applied tensile and compressive stresses. The measured elastic modulus was shown to increase to 65 +-6MPa with applied compressive stress (50 +-10MPa) and decrease to 32 +-9MPa with applied tensile stress (-50 +-10MPa). The response of the unstressed film was 47 +-6MPa throughout the measurement sequence demonstrating that this change in response is not due to any permanent change in the film. Elastic response was also found to vary as a function of work hardening, indentation position relative to morphological defects, and ion implantation dose. Results from these five experiments will be discussed in terms of possible mechanisms, in an effort to identify how stress alters the measurement process and causes the variation of Au's nano-mechanical properties. These experiments suggest that the IFM has the potential for being able to measure stress state on a very local level. The portion of this work done at Sandia, which is a multiprogram laboratory operated by Sandia Corporation--a Lockheed Martin Company, was supported by the United States Department of Energy under Contract DE-AC04-94AL85000.