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 H-2 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 alpha -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 D-2 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 Angstrom (2) and about 5% of the adsorbed D occurs in D-2 products. Subsurface alpha -D is abstracted at 680 K or higher temperatures with a cross section of 1.2 Angstrom (2). 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 D-2 product yield. At 100 K the HD cross section is only 2.2 Angstrom (2) (monodeuteride) or 1.4 Angstrom (2) (saturated surface), the HD kinetics is phenomenologically like that required by the ER mechanism, and a negligible quantity of D-2 is formed. The HA reaction model allows one to reproduce these features by adjusting the model parameters accordingly. (C) 2001 American Institute of Physics.