Enhanced formation of luminescent nanocrystal Si embedded in Si/SiO2 superlattice by excimer laser irradiation

Abstract

The effect of excimer laser annealing on the formation of luminescent nanocrystal Si ͑nc-Si͒ embedded in Si/SiO 2 superlattice is investigated. An amorphous Si/SiO 2 superlattice consisting of 20 periods of 2 nm thin Si layers and 5 nm thin SiO 2 layers was deposited on Si using electron cyclotron resonance plasma-enhanced chemical vapor deposition. Excimer laser annealing alone did not result in any nc-Si luminescence even at an energy density sufficient to melt the Si layers. However, if the nc-Si is preformed by a thermal anneal, subsequent excimer laser annealing will result in a threefold increase of the nc-Si luminescence intensity. The temperature dependence of the nc-Si luminescence spectrum, lifetime, and intensity indicates that excimer laser annealing activates luminescent nc-Si by removing defects and amorphous regions in thermally crystallized Si layers without significant changes in the size or shape of nc-Si.

Photoluminescent 1–2 nm Sized Silicon Nanoparticles: A Surface-Dependent System

“…Calcott’s model assuming a thermal equilibrium between two excitonic levels of different multiplicity and radiative constant, split by energy (Δ E ), is widely used in the literature to interpret the dependence with temperature of the radiative rate constant k r . ,,− At very low temperatures, almost all of the excitons are trapped in the lower state, whereas at higher temperatures, the excitons are in their upper state which is a dominant luminescent center. Reported Δ E values are on the order of 3 meV. , Considering that k r is expected not to vary with temperature for T > 200 K, decreasing PL intensities with increasing temperature have been attributed to the dominating role of nonradiative recombination. , Two main models were postulated to account for nonradiative thermally activated processes: a normal Arrhenius behavior , and the ionization of the excited state via tunneling through a potential barrier with a Berthelot-type T -dependence. ,− However, considering that our results show that ( k r + ∑ i k n i ) = τ –1 remains constant with temperature, k r being itself T -independent, competing nonradiative processes ∑ i k n i originated in the excitonic level are also expected to be temperature independent.…”

Temperature-dependent carrier recombination processes in nanocrystalline Si/SiO2 multilayers studied by continuous-wave and time-resolved photoluminescence

“…In order to obtain welldefined and intense light from Si NCs, it is very important to understand their light-emission mechanisms. Recently, radiative/nonradiative recombination processes of Si NCs or Si dots have been studied through the measurements of the temperature dependence of luminescence spectrum, lifetime and intensity by using time-resolved and continuous-wave (cw) photoluminescence (PL) spectroscopy [3][4][5][6][7]. These reports have suggested that the PL behaviours of Si NCs strongly depend on the observation energy and temperature.…”

“…These reports have suggested that the PL behaviours of Si NCs strongly depend on the observation energy and temperature. In particular, an increasing behaviour of PL with decreasing temperature has been frequently observed to be changed into a decreasing one at a characteristic temperature [3][4][5][6], but its origin is still under debate. In this study, ion beam sputtering deposition (IBSD) has been used to fabricate 50-period SiO 2 /SiO x multilayers (MLs), which have been subsequently annealed to form Si NCs in the SiO x layer.…”

Temperature-dependent photoluminescence of arsenic-doped Si nanocrystals

“…The non-radiative recombination rate is usually greater than phonon-assisted radiative recombination rate, and so the light emission efficiency from bulk Si is very low. In the past decade, a number of studies have been carried out to enhance the light emission from Si-based nanostructures such as Si/SiO 2 superlattices [7][8][9][10][11], Si nanocrystals [12][13][14][15][16], porous Si [17][18][19], and nano-patterned Si [20]. Among these Si nanostructures, Si nanocrystals have attracted great attentions due to the demonstration of efficient light-emitting devices [21][22][23][24] and the observation of stimulated emission [25][26][27][28][29].…”