Effect of pressure annealing on formation of light‐emitting Si nanocrystals in Si rich SiO₂

Abstract

Four types of Si rich SiO2 layers on the Si substrates have been prepared by Si ion implantation or by magnetron co‐sputtering of the Si and SiO2 targets. The types differed from each other in the contents of excess Si, which were about 5 at%, 15 at%, 25 at% and 35 at%. High temperature (up to 1100 °C) anneals of the samples were performed in neutral ambient under normal or elevated (up to 1.5 GPa) hydrostatic pressures. Photoluminescence spectroscopy, Raman scattering and electron diffraction were used for the characterizations. For the lowest concentration of the excess Si the high‐pressure annealing prevents the formation of the light‐emitting Si nanocrystals, but stimulates an appearance of the centers luminescing in the visible range. These centers are believed to be numerous Si nanoclusters, segregated from the oxide network. Increase in Si content provides during the high‐pressure anneals the formation of the quantum‐size Si nanocrystals able to emit strong PL near the wavelength of 800 nm. The effect of the high‐pressure annealing is ascribed to the enhanced energetically favorable segregation of Si from the oxide network. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Magnetron sputtered nanocomposite films of SI nanocrystals embedded in SIO2 for electronic and optoelectronic applications.

“…Take these two assertions into account, the high intensity of group D strongly suggests the formation of Si-Si long chains (Si clusters) where the Si is bonded to another Si ion in the as-deposited films. In addition, the Group D in the valance band XPS spectrum has also been observed by other researchers in their XPS study of the nc-Si embedded SiO 2 films, and is attributed to the formation of Si nanoclusters [12,13]. [12].…”

“…In addition, the Group D in the valance band XPS spectrum has also been observed by other researchers in their XPS study of the nc-Si embedded SiO 2 films, and is attributed to the formation of Si nanoclusters [12,13]. [12]. The increase in intensity and down shift of position imply that the probability that a given Si is surrounded by other Si atoms has increased, so does the probability of interaction between silicon orbitals [11].…”

“…In all cases, the charging effect can cause the core-level to shift to a higher binding energy [11,12]. As-discussed in Chapter 4, there are high concentrations of Si suboxides in the nc-Si embedded SiO 2 films even after high temperature annealing, and these Si suboxides mainly exist at the interfacial regions between the nc-Si and the SiO 2 matrix.…”

“…In the case of the films with excess Si, besides these three groups, an additional group D located at 1-4 eV above its valence-band edge is found. The additional group D is attributed to be the interaction between Si orbitals (i.e., Si 3p) which give states at these energies [12]. It is reported that for the SiOx films with chemical structure following the RBM the signal of group D can not be observed when the Si concentration is low (i.e.…”

Optical bistability in mesoporous silicon microcavity resonators

“…The identification of the exact physical mechanism of observed effects, such as strong visible and near-infrared luminescence, was complicated by conflicting experimental results that have been alternately ascribed to the quantum size effects [6][7][8], surface defects [9][10] and the presence of impurities [11]. Whilst this still remains a topic of debate [12], it is clear that the surface plays an important role in mediating many of the observed effects [13].…”