Defect engineering of Si nanocrystal interfaces

Abstract

The photoluminescence of Si nanocrystals is often assigned to exciton recombination confined within the nanocrystals. However, localized radiative or non‐radiative defects at the nanocrystal (NC) interface can drastically influence the NCs ensemble and reduce the luminescence output. In addition, size of the NCs as well as embedding host are playing a major role and have a significant influence on the optical properties. Here we summarize our work on size controlled Si NCs based on the SiOx/SiO2 superlattice approach. We will discuss how to distinguish between defects at the NC‐Si/SiO2 interface and defects in the matrix and demonstrate ways for effective NC surface passivation. The influence of different annealing ambient used for crystallization will be shown. Such perfectly defect passivated and size controlled samples will be used as a model system to discuss size dependent quantum properties such as the temperature dependent blue shift of the Si NC band gap.

Si nanocrystals and nanocrystal interfaces studied by positron annihilation

“…It is likely that in both samples (RF sputtered and PECVD grown), the annihilation states observed by PAS are related to dangling bond defects formed at the interface between the nanocrystal and the surrounding lattice. 10,18 On the other hand, the observed quantum confinement in this study clearly shows that PAS and PL measure different phenomena in contrast to the earlier study by Kilpel€ ainen et al…”

“…H 2 treatment further increases the PL intensity, which is attributed to the passivation of dangling bond defects at the SiNC/SiO 2 -interfaces. 12,18 Additionally, a small shift of PL peak towards higher wavelengths can be observed in the case of the passivated sample. This redshift is due to the emission enhancement from the larger nanocrystals of a given size distribution; larger nanocrystals are more prone to be affected by the non-radiative defects.…”

Effect of X‐ray irradiation on the blinking of single silicon nanocrystals

“…Interestingly, surface effects play a major role in the optical properties of silicon nanostructures, such as oxide‐passivated silicon nanocrystals (). In fact, it is believed that photoluminescence (PL) intermittency (blinking) observed for single Si‐NCs is the result of charge trapping/de‐trapping in the vicinity of the NC .…”

Photoluminescence and Stability of Sputtered SiOx Layers

“…[9][10][11] In addition, light emission may originate also from the substrate by laser-induced nonbridging oxygen hole centers (NBOHCs). [12] Achievement of efficient and controllable light emission in SiNCs would drastically enhance the development and use of Si-based optoelectronic devices due to their compatibility with mature Si-based electrical circuits.Various methods have been proposed so far to produce SiNCs embedded in different layers, such as plasma-enhanced chemical vapor deposition (PECVD), [13][14][15] electron beam (e-beam) evaporation, [16,17] ion implantation, [18,19] and sputtering. [20][21][22] Depending on the material and plasma settings, sputtering can provide homogeneous amorphous or crystalline layers with settable density.…”

“…Various methods have been proposed so far to produce SiNCs embedded in different layers, such as plasma-enhanced chemical vapor deposition (PECVD), [13][14][15] electron beam (e-beam) evaporation, [16,17] ion implantation, [18,19] and sputtering. [20][21][22] Depending on the material and plasma settings, sputtering can provide homogeneous amorphous or crystalline layers with settable density.…”