Raman-scattering elucidation of the giant isotope effect in hydrogen-ion blistering of silicon.
In this work, we investigate the origin of a giant isotope effect discovered in the blistering of hydrogen-ion-implanted and annealed silicon. Si(001) samples were implanted or co-implanted with 5 keV of H and/or D ions to total fluences of 2 x 10(16) and 6 x 10(16) ion/cm(2). The lower fluence is sufficient for blistering by pure H, but the higher one is required for the maximum blister coverage whenever D is involved. On these samples, we carried out Raman-scattering investigations of the evolution of Si-H/D complexes upon a stepwise thermal annealing from 200 to 550 degrees C. We have identified the critical chemical transformations characterizing the hydrogen-deuterium-induced blistering of silicon. The puzzling dependence on ion mass appears to be mainly connected with the nature of the radiation damage. We have found that H is more efficient in "preparing the ground" for blistering by nucleating platelets parallel to the surface, essentially due to its ability to agglomerate in the multihydride monovacancy complexes that evolve into hydrogenated extended internal surfaces. By contrast, D is preferentially trapped in the surprisingly stable monodeuteride multivacancies.
The effect of deuterium on the optical properties of free-standing porous silicon layers
We report our recent results of the effect of deuterium termination on the optical properties of porous Si nanostructures. The photoluminescence (PL) spectrum of deuterium-terminated porous Si (D-PS) was different from that of ordinary hydrogen-terminated porous Si (H-PS) although H-PS and D-PS show the same structure and the same absorption spectrum. We quantitatively discuss these results based on the trapping of conduction electrons at a surface Si-H or Si-D. In addition to these basic results, we also show that the replacement of hydrogen with deuterium reduces the PL degradation. Surface termination, especially photo-induced oxidation of the surface, was precisely studied by Fourier transform infrared absorption measurements.
Adsorption, abstraction, and pairing of atomic hydrogen on Si(100)-(2 x 1).
Using thermal desorption mass spectrometry, we have shown unambiguously that the adsorption of atomic hydrogen on Si(100)s2 3 1d leads to hydrogen pairing on silicon dimers at surface temperatures as low as 150 K and coverages as low as 0.2 monolayer. A detailed study of the adsorption kinetics shows a high probability of an abstraction reaction together with a coverage-dependent adsorption probability which is greater than expected for Langmuirian adsorption. These results, together with the known saturation coverage, are unified within the context of a “hot-precursor” mechanism for the adsorption of atomic hydrogen.