Nanocrystals Growth Control during Laser Annealing of Sn:(α-Si) Composites

Abstract

An efficient technique for low temperature metal-induced nanocrystalline silicon fabrication is presented. The technique is based on laser annealing of thin films of “amorphous silicon-tin” composites combined with in situ control and monitoring with Raman technique. Laser annealing was shown to provide the possibility of fine-tuning the nanocrystals size and concentration, which is important in photovoltaic and thermoelectric devices fabrication.

Tin-induced crystallization of amorphous silicon assisted by a pulsed laser irradiation

“…A larger dispersion of the Х С values (in comparison with distribution of nanocrystal sizes) is due to a greater statistical error in the calculation of this parameter. These results confirm the conclusions of recent work [23] about the irradiation intensity effect on the crystal size and concentration under MIC in SiSn-Si structures being influenced by continuous laser radiation. As can be seen from Fig.…”

“…After certain modes of laser treatments, there additionally appears the narrow band with a maximum within the range 500…520 сm -1 (b), which corresponds to the nanocrystalline phase of silicon [24,25]. This is the result of a MIC of amorphous silicon under the influence of laser irradiation [23]. Initial spectra of the simples Nos 1 to 6-2 contain both bands.…”

“…Knowing the power and duration of the laser pulses in both cases, it is easy to estimate and compare the density of the energy absorbed at crystallization threshold: is, in the case of more powerful laser irradiation, the beginning of the MIC requires an order of magnitude less energy. This can be explained in at least two ways: stimulating influence of photoionization [23,26] or greater heating by a nanosecond pulse as compared with microsecond pulse in the consequence of heat transfer inertia. Fig.…”

“…According to this mechanism, silicon nanocrystals are formed due to cyclic repetition of formation and decomposition of a supersaturated silicon in tin solution on the narrow eutectic layer at a-Si/Sn interface of tin micro-droplets in amorphous Si volume. The tin-induced crystallization of amorphous silicon can be stimulated by the action of laser light [23]. This allows us to measure the temperature, size and volume fraction of nanocrystals in the process of their formation by Raman scattering and simultaneously to control the crystallization process by changing the intensity and duration of laser radiation.…”

Tin-Induced Crystallization of Amorphous Silicon under Pulsed Laser Irradiation

“…In work [23], it was shown that the process of tin-induced crystallization of amorphous silicon can be stimulated by laser irradiation. This fact allows the Raman scattering to be used in order to measure the temperature, size of nanocrystals, and volume occupied by them in the course of their formation.…”