Molecular hydrogen is alternately introduced into and removed from the gate oxide of irradiated metal-oxide-semiconductor field-effect transistors at room temperature by changing the ambient between forming gas (10/90% H2/N2) and nitrogen. Using charge pumping, it is observed that H2 causes a simultaneous buildup of interface states and decrease of trapped positive charge. The results are explained by a reaction sequence in which H2 is cracked to form mobile H+, which under positive bias drifts to the Si/SiO2 interface, and reacts to produce a dangling-bond defect. The rate limiting step over most of the time domain studied is the cracking process. Two types of cracking sites are modeled by molecular orbital calculations: oxygen vacancies (E′ centers) and broken bond hole traps (BBHTs). Initial- and final-state energies, as well as the activation energies, are calculated. The calculations indicate that the latter is the more likely H2 cracking site. The combined experimental and theoretical results suggest that at least 15% of the trapped positive charge is at sites similar to the BBHT sites. Implications of the model and similarities between interface-state formation by cracked H2 and irradiation are discussed.

Atomic-layer-deposited layers of Al2O3 on (100)Si are shown to transform into γ-Al2O3 when treated at temperatures above 800 °C. The compaction process leads to widening of the alumina band gap and causes an ≈0.5 eV upward shift of the oxide conduction band with respect to the Fermi level of Au and Al. In the case of incomplete transformation of the Al2O3 film, large leakage currents across the oxide are observed, which are explained by the formation of conducting grain boundaries similar to those formed on γ-alumina surfaces.

The stacking sequence and interplane and interlayer separation of 2H-MoS2 and 28-NbSe2 are determined by the dynamical low-energy-electron diffraction approach. Although lateral reconstructions corresponding to alteration in the bulk stacking sequence at the surface are physically reasonable, we find that such reconstructions do not in fact occur for these two compounds. 15

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Spectroscopic ellipsometry was used to determine the density of oxides thermally grown on Si substrates as a function of the oxidation temperature, and the time and temperature of postoxidation anneals. All the oxides were found to be denser than fused silica. The density of the as-grown oxides was found to decrease as the growth temperature was increased. Postoxidation anneals were found to reduce the oxide density; high temperature or long-time anneals caused the greatest reduction in density. Holes alone, or holes and electrons, were injected into the oxides by irradiating with vacuum ultraviolet light or x rays under electric field bias. Using capacitance–voltage measurements, it was found that low-density oxides trap charge more efficiently than high-density oxides. Electron spin resonance measurements indicated that, for most of these oxides, the number of paramagnetic defects was substantially smaller than the number of trapped charges. It is hypothesized that the additional, nonparamagnetic, charge is in the form of protons trapped near network oxygen atoms that have large Si–O–Si bond angles. The number of these large-angle bonds in the near-interfacial oxide increases as the oxide density decreases, explaining the observed correlation between the charge trapping and the oxide density.