The process of electromigration in thin Al films was studied directly by transmission electron microscopy during passage of current. Due to electromigration, the Al ions migrate along the test strip from cathode to anode, and the actual opening up of holes near the cathode was observed. The rate of hole formation was used to measure an activation energy. For the test strips, a value of 0.7 eV was obtained. In addition, some physical aspects of hole formation, as well as material buildup in the form of hillocks and single-crystal Al whiskers, were observed. Some of the whiskers, which were less than 1 μ in diameter, were seen to grow to unusual lengths, occasionally exceeding 50 μ.

Electrotransport in thin Al strips was directly observed by transmission electron microscopy. As expected, hole formation was seen in regions where the electron flow was in the direction of increasing temperature. Hillocks and whiskers were seen to form where the electron flow was in the direction of decreasing temperature. Ciné films taken of the process show the holes to grow predominantly by a transverse movement of narrow fingers which ultimately coalesce and lead to a catastrophic strip burn-out.

The lattice distortions in single-crystal Si substrates due to stressed surface films were calculated by linear elastic theory. It is shown that the strains are localized directly underneath discontinuities in the films, and these regions are responsible for the enhanced diffracted intensity experimentally observed in x-ray topographs of the substrate. A simplified theory is presented which is used to semiquantitatively describe the relationship between film stress and thickness, and enhanced diffracted intensity.

Diffraction topographs of oxidized silicon wafers made by the extinction contrast technique show extremely high intensity being diffracted from the silicon surface directly under steps etched in the oxide. Edges of metal or dielectric films evaporated on silicon similarly show enhanced intensity. In some cases, a decreased diffracted intensity (less than that diffracted by pure Si) is seen in these regions. These two effects are attributed to elastic strain transmitted to the Si by the step or edge, due to the adherence of the film to the substrate. Enhanced intensity is due to extinction contrast, while decreased intensity is due to a Borrmann anomalous transmission effect. The orientation of the step with respect to the diffraction vector ghkl, the height of the step, and the compositions of substrate and film are shown to be important parameters affecting the diffracted intensity.

A technique is presented for preparing transmission electron microscope samples of gallium arsenide by a combination of chemical and electrolytic polishing. Both A(111) and B(1̄1̄1̄) as well as {100} surfaces of wafers obtained from two sources were examined by transmission electron microscopy after a variety of surface treatments. In general, B(1̄1̄1̄) and {100} surfaces were damaged more heavily than A(111) surfaces by mechanical polishing with 1-μ diamond. Aside from the surface damage the crystals were remarkably dislocation free, although precipitates of different kinds were observed. One type of precipitate clusters in the shape of tori, and can be revealed in the optical microscope by lightly electropolishing a mechanically polished wafer or by etching a polished wafer in the Sirtl etch. The other type of precipitate has contrast in the electron microscope similar to stacking faults, and may be due to an oxide of some type.