Trap states in oxidation layer of nanocrystal Si

Abstract

The photoluminescence (PL) of nanocrystal present in porous silicon shifts from the near infrared to the ultraviolet depending on the size when the surface is passivated with Si-H bonds. After oxidation, the centre wavelength of PL band is pinned in a region of 700–750 nm and its intensity increases obviously. Calculation shows that trap electronic states appear in the band gap of a smaller nanocrystal when Si = O bonds or Si–O–Si bonds are formed. The changes in PL intensity and wavelength can be explained by both quantum confinement and trap states in an oxidation layer of nanocrystal. In the theoretical model, the most important factor in the enhancement and the pinning effects of PL emission is the relative position between the level of the trap states and the level of the photoexcitation in the silicon nanocrystal.

Environmental photostability of SF6-etched silicon nanocrystals

“…However, the photobleaching effect is exacerbated when these SiNCs are irradiated in air and oxidize. It was shown [57] that, when SiNCs oxidize, the Si-Si bonds can be fractured due to large stresses present at the surface. Furthermore, the oxidation process can lead to the formation of localized states in the bandgap [57][58][59] of the H-terminated SiNCs, which may cause a further decrease in the PLQY.…”

“…It was shown [57] that, when SiNCs oxidize, the Si-Si bonds can be fractured due to large stresses present at the surface. Furthermore, the oxidation process can lead to the formation of localized states in the bandgap [57][58][59] of the H-terminated SiNCs, which may cause a further decrease in the PLQY. Therefore, the significant loss in PLQY observed in the UV-exposed and oxidized H-terminated SiNC may be the result of bond breaking due to the UV photons and the creation of localized states in the bandgap.…”

Ab Initio Calculations of Chitosan Effects on the Electronic Properties of Unpassivated Triangular ZnO Nanowires Oriented along [0001] Directions

“…The value of the corresponding band gap is 1.42 eV, which is very similar to the work of Hu et al However, when the CS is colocalized in P 1 and P 2 , one and two flat states below the Fermi level are observed. These types of states have been previously studied by Cuevas et al and Huang et al in binary semiconductors and Si nanocrystals and are attributed to Si–H–Si bridges and the interaction of oxygen with the NW surface. Therefore, a localized state is expected to exist in the nanowire surface where CS interacts.…”

Effects of lithium on the electronic properties of porous Ge as anode material for batteries

“…The pGe was modeled according to the supercell Scheme [53][54][55][56] by removing columns of atoms in the [001] direction from an otherwise perfect Ge crystal. This orientation was chosen since it is the most commonly reported by the majority of the investigations specialized in the synthesis of pGe.…”