Single‐crystal Si films have been grown on Si(001)2×1 substrates by ultraviolet (UV) photostimulated atomic‐layer epitaxy (ALE) from Si2H6. The ALE deposition rate R per growth cycle remains constant at 0.4 monolayers (ML), 1 ML=6.8×1014cm−2, over a wide range of deposition parameters: growth temperature (Ts=180 –400 °C), Si2H6exposure (peak pressure during gas pulse=0.1–5 mTorr), UV laser energy density (E=250–450 mJ cm−2whereEmaxis determined byTs), and number of UV laser pulses per cycle. A film growth model, based upon the results of the present deposition experiments and Monte Carlo simulations, together with our previous adsorption/desorption measurements, is used to describe the reaction pathway for the process. Si2H6is dissociatively adsorbed on Si surface dimers as two SiH3radicals which subsequently dissociate to SiH2and H. Site blocking during the adsorption and surface dissociation steps limits the surface coverage to 2.9×1014SiH2cm−2(hence,R=0.43 ML per cycle). The H terminated silylene‐saturated surface is thermally stable and passive to further Si2H6exposure. ArF or KrF laser pulses (≊20 ns) are used to desorb H, following a Si2H6exposure, and the growth cycle is repeated until the desired film thickness is obtained. AtTs400 °C, H is thermally desorbed and pyrolytic growth competes with ALE. Plan‐view and cross‐sectional transmission electron micrographs together with selected‐area and convergent‐beam electron diffraction patterns show that the ALE films are epitaxial layers with no observed extended defects or strain.