The conduction band offset of the type II heterostructure CdS/ZnSe is determined from photoluminescence data of single quantum wells. The cubic quantum well samples have been grown by compound-source molecular-beam epitaxy. Photoluminescence spectra were measured at low temperatures and evaluated by fitting an effective mass model to the transition energies. A conduction band offset of (0.80 ± 0.1) eV and an effective electron mass for cubic CdS of (0.18 ± 0.05)m 0 were determined.

The interaction of H atoms with Si(111) surfaces with respect to adsorption, abstraction, and etching was investigated using thermal desorption and product detection techniques. The study covers a wide range of coverages and the temperature range 100–1000 K. After H admission to Si(111) at 100 K in H2 desorption spectra decomposition of trihydride (t), dihydride (d), and monohydride (m) was observed around 455, 700, and 820 K, respectively. Adsorption of H at 380 K leads to desorption from d and m, and after admission of H at 680 K desorption from m was observed. The kinetics of m, d, and t desorption is according to first-order kinetics, only the m peak exhibits at small coverages second-order phenomenology. H exposure above 400 K leads to desorption of subsurface α-hydrogen at 920 K in thermal desorption spectra. Nonstationary etching via silane formation was monitored around 630 K. The nonstationary silane etch peak occurs through a quasi-first-order process in the admission temperature range 100–500 K and assumes a second-order phenomenology at admission temperatures between 500 and 600 K. This silane is formed through the recombination of surface silyl (t) and H in silylene (d) groups. Its yield decreases with the temperature at which H was admitted and is negligible after admission above 620 K since silyl groups are no longer available on the surface. Stationary etching during subjecting the surface with a continuous H flux occurs via a direct reaction step between the incoming H and surface silyl groups. The stationary etch yield decreases from 200 to 600 K due to depletion of surface silyl groups. In parallel to stationary etching, H abstraction proceeds with much higher probability. The kinetics of D abstraction by H from the monodeuteride phase at 680 K, measured through the HD product rate, as well as the formation of homonuclear D2 products contradict the operation of an Eley–Rideal (ER) mechanism, but are in excellent agreement with the solutions of a hot-atom (HA) reaction kinetic model which was recently successfully applied to abstraction on metal surfaces. This model is based solely on hot-atom processes and includes competition of reaction and sticking of hot atoms. Four parameters are needed to reproduce the measured HD rate data. At 680 K the abstraction cross section is 3.2 Å2 and about 5% of the adsorbed D occurs in D2 products. Subsurface α-D is abstracted at 680 K or higher temperatures with a cross section of 1.2 Å2. Abstraction at lower temperatures, either from monodeuteride surfaces or from surfaces saturated with di- and trideuteride proceeds with a smaller cross section and a reduced D2 product yield. At 100 K the HD cross section is only 2.2 Å2 (monodeuteride) or 1.4 Å2 (saturated surface), the HD kinetics is phenomenologically like that required by the ER mechanism, and a negligible quantity of D2 is formed. The HA reaction model allows one to reproduce these features by adjusting the model parameters accordingly.

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