Nalini et al. Nanoscale Research Letters 2011, 6:156 http://www.nanoscalereslett.com/content/6/1/156 spectrum recorded after annealing the multilayer struc- tures for 1 min at 1000°C (RTA). The response of the multilayers to this annealing treatment shows almost a reversed trend of what was observed in the case of clas- sical annealing treatment. It can be noted that the SRSO/SiNx has the highest intensity. No PL emission has been recorded from the SRSO/SiO2 system. We may note from the figures that the luminescence peak arising from the SiNx/SiO2 structure around 1.9 eV is the same whatever the annealing temperature. The fit- ting of the PL curve recorded from the SRSO/SiNx film evidences the presence of two emission bands centered at 1.65 and 1.37 eV. Though this result is interesting and shows the possibility of exploiting SRSO alternated with the SiNx sublayer to achieve a control over the thermal budget, it also has to be mentioned that the PL intensity obtained is one order of magnitude lower than the emission of SRSO/SiO2 subjected to classical anneal- ing. Hence, two methods of fabrication were attempted with the aim of increasing the PL intensity: (i) increasing the SiNx sublayer thickness to 5 nm and (ii) doubling the number of periods, i.e., fabricating 100 periods of 3.5 nm SRSO alternated with 5 nm SiNx. Figure 3 Page 3 of 5 shows the effect of the aforesaid fabrication methods on the PL spectrum of the SRSO/SiNx multilayers. All the spectra have been normalized to 100 nm thickness for comparison. The interference effect in PL intensity has been also investigated by the previously mentioned method PL intensity from both 50 periods multilayers should be decreased by about 15%, in order to take into account the enhancement effect due to maxima of inter- ference. The first method adopted reveals that the SiNx thickness has some significant contribution toward the luminescence. There is a slight change in the emission wavelength from 1.59 eV with 3.5 nm SiNx sublayer to 1.55 eV in the case of 5 nm SiNx sublayer. Irrespective of the number of periods deposited, for a given sublayer thickness the wavelength of emission peak remained constant. It is interesting to note that the emission intensity increases with the SiNx thickness. This result motivated toward trying out the second method men- tioned and it can be noticed that the PL signal increases 7.4 times when the number of (3.5 nm)SRSO/(5 nm) SiNx pattern is increased from 50 to 100. For that case one can notice is the presence of a small peak between 1.90 and 1.65 eV and another one around 1.5 eV. The inset in Figure 3 shows a comparison between the SRSO/SiO2 annealed at 1 h-1100°C and SRSO/SiNx structure subjected to RTA. One can notice that the emission peak from the SRSO/SiNx system shifts in the visible region and this is one of the advantageous aspects for the solar cell application. It is very interest- ing to note that the SRSO/SiNx annealed for a very short time of 1 min at 1000°C is 1.43 times more intense than the SRSO/SiO2 structure annealed for a Figure 2 Effect of annealing treatment on the PL intensity of the multilayer structures. Figure 3 Effect of sublayer thickness and total thickness of SiNx on the PL spectrum on RTA. (Inset: comparison between the SRSO/SiO2 annealed at 1 h-1100°C and SRSO/SiNx structure subjected to RTA).