ИСТИНА

Er-doped materials containing Si nanoparticles are of particular interest in the view of constructing a novel Si-based light emitting devices at 1.54-μm, which corresponds to the absorption minimum of standard optical fiber. Recent investigations showed that amorphous silicon nanoclusters can efficiently sensibilize Er3+ ions photoluminescence (PL), providing better PL yield at 1.54-μm as compared with well known sensitizers – Si nanocrystals [1]. This fact brings up the question about the mechanism of Er3+ ions excitation in both structures with amorphous (a-Si-NCs) and crystalline silicon nanoclusters (c-Si-NCs). As it was shown before, even in c-Si-NC:Er systems the ‘slow’ energy transfer process from silicon nanocrystals does not play a dominant role in Er3+ ions sensitization in contrary to some ‘fast’ excitation process, which was found to be similar to the energy transfer in bulk-Si:Er structures [2]. The main goal of our study was to deeper understand the role of crystalline and amorphous Si-NCs in the processes of both excitation and deexcitation of Er3+ ions. In present work the comparative study of optical properties was made for the Er-doped structures with amorphous and crystalline Si nanoclusters in SiO2 matrix. Samples were fabricated by the thermal deposition of SiO and SiO2 layers on Si substrate [3]. Subsequent thermal annealing for 1 hour under N2 atmosphere at 1100 оС and 900 оС resulted in c-Si-NCs and a-Si-NCs formation within SiO layers, correspondingly. Erbium was implanted with the doses from 1•10^14 to 7•10^15 cm-2. In addition part of the samples was annealed for 1 hour under N2/H2 (5% H2) atmosphere at 450 оС in order to investigate the influence of Si/SiO2 interface defects passivation [4] on photoluminescence of Er3+ ions. The following main results were obtained. First, we found that PL intensity at 1.54-μm was almost equal for samples with amorphous and crystalline Si-NCs and depended mainly only on erbium implantation dose. Second, there was not registered a considerable difference between Er-related PL excitation spectra for both types of structures, which argues for the same mechanism of erbium ions sensibilization. Third, we observed a significant (from 48% to 67% depending on implantation dose) increase in Er-related PL lifetime for a-Si-NC:Er samples in comparison with c-Si-NC:Er ones, which indicates on the less efficiency of nonradiative recombination of Er3+ ions in former structures. Finally, the main effect of Si/SiO2 interface defects passivation resulted in Si-NCs-related PL intensity increase (from 2 to 3 times), while Er-related PL intensity remained almost unaltered. Moreover, we detected a pronounced (about 20%) decrease in Er-related PL lifetime for c-Si-NC:Er structures due to the passivation procedure. In our opinion these unobvious results point out the important role of c-Si-NCs in deexcitation of Er3+ ions. 1. G. Franzo, S. Boninelli, D. Pacifici, et al., Appl. Phys. Lett. 82, 3871 (2003). 2. M. Fujii, K. Imakita, K. Watanabe, et al., J. Appl. Phys. 95, 272 (2004). 3. M. Zacharias, J. Bläsing, P. Veit, et al., Appl. Phys. Lett. 74, 2614 (1999). 4. S. Godefroo, M. Hayne, M. Jivanescu, et al., Nature Nanotech. 3, 174 (2008).