Interface Science of Controlled Metal/Metal and Metal/Ceramic Interfaces Prepared using Ultrahigh Vacuum Diffusion Bondi
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INTERFACE SCIENCE OF CONTROLLED METAL/METAL AND METAL/CERAMIC INTERFACES PREPARED USING ULTRAHIGH VACUUM DIFFUSION BONDING WAYNE E. KING, G. H. CAMPBELL, A. W. COOMBS, G. W. JOHNSON, B. E. KELLY, T. C. REITZ, S. L. STONER, W. L. WIEN, AND D. M. WILSON Chemistry and Materials Science Department, University of California, Lawrence Livermore National Laboratory, Livermore, CA 94550 ABSTRACT We have designed, constructed, and are operating a unique capability for the production of highly controlled homophase and heterophase interfaces: an ultrahigh vacuum diffusion bonding machine. This machine is based on a previous design which is operating at the Max Planck Institut for Metallforschung, Institut fir Werkstoffwissenschaft, Stuttgart, FRG. In this method, flat-polished single or polycrystals of materials with controlled surface topography can be heat treated up to 1500'C in ultrahigh vacuum. Surfaces of annealed samples can be sputter cleaned and characterized prior to bonding. Samples can then be precisely aligned crystallographically to obtain desired grain boundary misorientations. Material couples can then be bonded at temperatures up to 1500'C and pressures up to 10 MPa. Results are presented from our initial work on Mo grain boundaries and Cu/A120 3 interfaces. INTRODUCTION The lack of well characterized, precisely oriented interfaces has been identified as limiting the capability of the Interface Science community to make progress in the study of structure and properties of interfaces. Lawrence Livermore National Laboratory and Sandia National Laboratories are developing a multi-disciplinary, multi-institutional research effort in interface science. This research, which focuses on the influence of impurities, flaws, and inclusions on adhesion and bonding at internal interfaces will rely on the availability of bicrystals with well defined interfacial chemistry and highly reproducible misorientations. The capability to produce such bicrystals did not exist within the United States although it is critical to further advancement of interface science and technology. BACKGROUND To address this need we have selected the diffusion bonding approach, which was successfully demonstrated at the Max Planck Institut in Stuttgart, for application to the class of interface problems of interest. 1 ' 2 Figure 1 shows a rendering of the design of the IJIHV diffusion bonding machine. It comprises four chambers: a surface analysis chamber, a diffusion bonding chamber, an annealing chamber, and a surface modification chamber (not shown). typically, a sample is first introduced into the annealing chamber via either an airlock chamber (Figure 2). The sample is annealed in ultrahigh vacuum to 1500'C to stabilize the microstructure. After annealing, a rail system transports the sample to the surface analysis chamber, to the surface modification chamber, or to the bonding chamber. A special manipulator (see the Figure 3) moves the sample to the railroad car. In the surface analysis chamber (Figure 4), sample surfaces are sputter-cleaned
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