Intermetallic phases formed along a Sn-Ag eutectic solder/Cu interface during solid-state aging have been characterized and the activation energies of Cu3Sn and Cu6Sn 5 growth have been calculated. Diffusion couples consisting of Cu/ 96.5Sn-3.5Ag/Cu were aged at 110 to 208~ for 0 to 32 days. After aging, the Cu/ solder interfaces were examined using scanning electron microscopy and energy dispersive x-ray spectroscopy. The growth rate constants for each intermetallic layer were calculated assuming a simple parabolic diffusion-controlled growth model. The activation energy for Cu3Sn growth is 0.73 eV/atom and the activation energy for Cu6Sn 5 growth is 1.11 eV/atom.

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Scanning tunneling microscopy (STM) has been used to obtain images and current–voltage (I–V) curves of carbon nanotubes produced by arc discharge of carbon electrodes. The STM I–V curves indicate that carbon nanotubes with diameters from 2.0 to 5.1 nm have a metallic density of states. Using STM, we also observe nanometer-size graphene sheets which are four graphite layers thick. The STM images of carbon nanotubes are in good agreement with transmission electron microscope images.