Showing papers by "P. Baeri published in 1989"
TL;DR: In this article, it was shown that laser irradiation in a narrow energy density range results in the formation of a novel epitaxial NiSi phase on (111) Si.
Abstract: Thermally grown NiSi layers on (111) Si substrates have been irradiated by 35‐ns Nd laser pulses in the energy density range of 0.3–2.0 J/cm2. The duration of the laser‐induced melt was monitored in situ by transient reflectivity measurements. Samples have been subsequently analyzed by Rutherford backscattering in combination with channeling and by transmission electron microscopy. It is shown that laser irradiation in a narrow energy density range results in the formation of a novel epitaxial NiSi phase on (111) Si. Electron microscopy studies show that this silicide phase could have a cubic symmetry with a lattice constant very similar to that of Si. This phase is, however, metastable and it transforms into the orthorhombic one upon thermal annealing at about 300 °C.
16 citations
TL;DR: Experimental data and thermodynamic evaluations indicate that when the As concentration approaches an upper limit of about 15 at.
Abstract: Si-As supersaturated solid solutions obtained by ion implantation on 〈100〉- and 〈111〉-oriented Si substrates and laser annealing have been made amorphous by pulsed-laser irradiation. The transition to the amorphous phase has been detected in situ by time-resolved reflectivity measurements, which demonstrated that it takes place via a liquid phase as in the case of pure Si. Heat-flow computations have been employed to correlate irradiation parameters with the solidification velocity. The critical liquid-solid interface velocity to grow amorphous layers is much lower for the Si-As solution than for pure silicon. It decreases from 5 to 3 m/s with increasing As concentration from 8 to 13 at. %. Moreover, it is a factor 1.5 smaller for the 〈111〉 substrates than for the 〈100〉 ones. We explain this effect in terms of the difference between the crystalline and the amorphous melting temperature decreasing with increasing As concentration. The results are consistent with an evaluation of the free energy of Si-As solutions performed by assuming a heat of solution in the amorphous phase lower than in the crystal phase. Both experimental data and thermodynamic evaluations indicate that when the As concentration approaches an upper limit of about 15 at. % only the liquid-amorphous transition is possible since the free energy of the crystal and the amorphous phase tend to coincide.
11 citations
TL;DR: In this article, the difference in the melting temperature of ion implanted and relaxed amorphous silicon has been measured and the threshold energy density for surface melting was found 15.9±.3% higher than that in the unrelaxed one.
Abstract: The difference in the melting temperature of ion implanted and relaxed amorphous silicon has been measured. Pulsed laser irradiation (λ=347 nm, τ=30 ns) has been used to induce surface melting in the amorphous layer and time resolved reflectivity to detect the melting onset. The threshold energy density for surface melting in the relaxed amorphous was found 15.9±.3% higher than that in the unrelaxed one. The estimate of the variation of the thermal parameters in amorphous silicon upon relaxation allowed a determination of ΔTM=45±10 K between relaxed and unrelaxed amorphous silicon.
2 citations