AVS 50th International Symposium
    Thin Films Friday Sessions
       Session TF-FrM

Paper TF-FrM4
Mechanical Properties of Reacted Metal Multilayers

Friday, November 7, 2003, 9:20 am, Room 329

Session: Mechanical Properties of Thin Films
Presenter: D.P. Adams, Sandia National Laboratories
Authors: D.P. Adams, Sandia National Laboratories
M. Rodriguez, Sandia National Laboratories
J.B. Kelley, Sandia National Laboratories
T. Covert, Sandia National Laboratories
T. Buchheit, Sandia National Laboratories
M. Grubelich, Sandia National Laboratories
Correspondent: Click to Email
Sputtered multilayer thin films composed of reactive material pairs are currently of interest for brazing, joining and other energetic applications. As shown extensively by Weihs et.al. several thin film material systems can be stimulated such that a rapid, self-propagating reaction occurs within a multilayer. This alloying reaction has great potential for joining, because it prevents global heating of parent materials. In this talk, we evaluate the resultant mechanical properties and microstructure of three different reacted multilayer systems. This includes Ni/Ti, Al/Pt and metal/B multilayers. Each material system was deposited by magnetron sputtering to thicknesses in excess of 1 m. First, we describe how the propagation velocity depends on multilayer design. Propagation velocities are measured by imaging the propagating reaction front using a high speed Cordin camera and strobe light assembly. Velocities in excess of 50 m/s are measured for some multilayer designs. We determine how changes in stoichiometry (specifically deviations from the targeted composition) affect velocity. Secondly, we discuss the stress in reacted films. Laser-based wafer curvature techniques are used to determine average in-plane stress in reacted films. Stresses in excess of 1 GPa have been measured for several reacted multilayers. To better understand the development of stress in these systems we have conducted x-ray diffraction to determine coefficients of thermal expansion. Films achieve extremely high temperatures during self-propagating reactions and extrinsic stress largely determines final stress state; this can greatly affect their usefulness in a braze process. Additional mechanical properties such as hardness are measured, and these are related to film microstructure probed by transmission electron microscopy.