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Single-crystal Si films have been grown on Si(001)2×1 substrates by UVphotostimulated atomic-layer epitaxy (ALE) from Si2H6. The ALE deposition rate R per growth cycle remains constant at 0.4 monolayers (ML) over a wide range of deposition parameters: growth temperature (Ts= 180–400 °C), Si2H6 exposure (peak pressure during gas pulse = 0.1−5 mTorr), laser energy density ( = 250–450 mJ cm−2 where is determined by Ts), and number of UV laser pulses per cycle. A film growth mocrel, 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. The Hterminated silylene-saturated surface formed by adsorption and desorption of disilene is thermally stable and passive to further Si2H6 exposure. ArF or KrF laser pulses (≅20 ns) are used to desorb H, following a Si2H6 exposure, and the growth cycle is repeated until the desired film thickness is obtained. At Ts < 180 °C, the growth process becomes rate limited by the surface dissociation step and R decreases exponentially as a function of 1/Ts with an activation energy of ≅0.5 eV. At Ts > 400 °C, H is thermally desorbed and pyrolytic growth competes with ALE. Transmission electron micrographs together with selected-area electron diffraction patterns show that the ALE films are epitaxial layers with no observed extended defects or strain.

L149neous chemical reaction caused by the pretreatment of the electrode.The conversion efficiency of the cell (Ru(bpy)~+: 5 raM, Fe~+: 10 mM) with back-illumination was 0.04%, which is a little greater than the highest previously reported value of 0.03%. 18 It was much improved when almost all the incident light was absorbed within the diffusion layer perpendicular to the IDA electrode surface, which is roughly estimated from the distance between the centers of adjacent band electrodes. Cell performance strongly depends on both IDA geometry and the absorbance (or concentration) of the electrolyte. Higher levels of performance will be achieved when an IDA with a wider bandwidth but a smaller gap width is applied to a higher concentration electrolyte. A theoretical study of photogalvanic cells 5 using the method applied in a photochemical study including electrode geometry 19 will lead to the optimum conditions for obtaining the optimum performance.

Scanning tunneling microscopy has been employed to study the adsorption of disilane (Si2H6) and pyrolytic growth on Si(100)-(2X1) at various temperatures. Room-temperature exposures result in a random distribution of dissociation fragments on the surface. Formation of anisotropic monohydride islands and denuded zones as well as island coarsening is observed at higher temperatures. The results are strikingly similar to those reported for growth by molecular-beam epitaxy using pure Si, even though different surface reactions are involved in these two growth processes.