The classical theory of Cabrera–Mott describes passivation film formation on metals, where they predicted that this film grows as a uniform layer due to a field-enhanced ionic transport mechanism. Here we present experimental evidence, based on in situ transmission electron microscopy of copper oxidation, that the passivation film nucleates and grows as oxide islands, not as a uniform layer. We propose an alternative phenomenological theory to describe passivation film formation, based on island growth followed by coalescence.

Terahertz absorption in waveguides loaded with InAs/AlSb super-superlattice mesas reveals a frequency dependent crossover from loss to gain that is related to the Stark ladder produced by an applied dc electric field. Electric field domains appear to be suppressed in the super-superlattice composed of many very short segments of superlattice, interrupted by heavily doped InAs regions. Resonant crossover is indicated by an increase in terahertz transmission as the Stark splitting or Bloch frequency determined by the applied dc electric field exceeds the measurement frequency.

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By studying the growth of Cu2O islands during the initial oxidation stage of Cu(001) with in situ transmission electron microscopy, it is found that the dominant mechanism for the growth of three-dimensional islands is surface diffusion of oxygen. However, there exists a non-negligible contribution to the metal oxide growth by another mechanism, probably direct impingement of the oxygen atoms on the oxide island. These results demonstrate the importance of surface conditions in oxidation.

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