Polarized internal reflection spectroscopy has been used to characterize HF-treated Si(111) surfaces. The silicon-hydrogen stretching vibrations indicate that the surface is well ordered, but is microscopically rough, with coupled monohydride, dihydride, and trihydride termination.

Near-edge and extended x-ray-absorption fine-structure measurements from a wide variety of oxidized Si nanocrystals and H-passivated porous Si samples, combined with electron microscopy, ir absorption, forward recoil scattering, and luminescence emission data, provide a consistent structural picture of the species responsible for the luminescence observed in these systems. For porous Si samples whose luminescence wavelengths peak in the visible region, i.e. , at (700 nm, their mass-weighted-average structures are determined here to be particles (not wires) whose short-range character is crystalline and 0 whose dimensionstypically (15 Aare significantly smaller than previously reported or proposed.Results are also presented which demonstrate that the observed visible luminescence is not related to either a photo-oxidized Si species in porous Si or an interfacial suboxide species in the Si nanocrystals. The structural and compositional findings reported here depend only on sample luminescence behavior, not on how the luminescent particles are produced, and thus have general implications in assigning quantum confinement as the mechanism responsible for the visible luminescence observed in both nanocrystalline and porous silicon.

We have investigated the fundamental mechanism underlying the hydrogen-induced exfoliation of silicon, using a combination of spectroscopic and microscopic techniques. We have studied the evolution of the internal defect structure as a function of implanted hydrogen concentration and annealing temperature and found that the mechanism consists of a number of essential components in which hydrogen plays a key role. Specifically, we show that the chemical action of hydrogen leads to the formation of (100) and (111) internal surfaces above 400 °C via agglomeration of the initial defect structure. In addition, molecular hydrogen is evolved between 200 and 400 °C and subsequently traps in the microvoids bounded by the internal surfaces, resulting in the build-up of internal pressure. This, in turn, leads to the observed “blistering” of unconstrained silicon samples, or complete layer transfer for silicon wafers joined to a supporting (handle) wafer which acts as a mechanical “stiffener.”

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In situ multiple internal reflection infrared absorption spectroscopy of H-passivated silicon surfaces in controlled oxygen environments reveals that direct oxygen incorporation into the surface Si–Si bonds occurs without surface hydrogen removal, in the temperature range of 550–590 K for 1–20 mTorr O2 pressures. The kinetics of the O2 insertion process display overall effective activation energies of 1.6 to 1.7 eV and prefactors controlled primarily by Si–H steric hindrance for O2 to access Si–Si backbonds.