| 1. |
- Nestoklon, Mikhail O., et al.
(författare)
-
Tight-binding calculations of the optical properties of Si nanocrystals in a SiO(2)matrix
- 2020
-
Ingår i: Faraday discussions. - : Royal Society of Chemistry (RSC). - 1359-6640 .- 1364-5498. ; 222:0, s. 258-273
-
Tidskriftsartikel (refereegranskat)abstract
- We develop an empirical tight binding approach for the modeling of the electronic states and optical properties of Si nanocrystals embedded in a SiO(2)matrix. To simulate the wide band gap SiO(2)matrix we use the virtual crystal approximation. The tight-binding parameters of the material with the diamond crystal lattice are fitted to the band structure of beta-cristobalite. This model of the SiO(2)matrix allows us to reproduce the band structure of real Si nanocrystals embedded in a SiO(2)matrix. In this model, we compute the absorption spectra of the system. The calculations are in an excellent agreement with experimental data. We find that an important part of the high-energy absorption is defined by the spatially indirect, but direct ink-space transitions between holes inside the nanocrystal and electrons in the matrix.
|
|
| 2. |
- Zhou, Jingjian, et al.
(författare)
-
Photoluminescence Intensity Enhancement of Single Silicon Quantum Dots on a Metal Membrane with a Spacer
- 2020
-
Ingår i: Physica Status Solidi (a) applications and materials science. - : WILEY-V C H VERLAG GMBH. - 1862-6300 .- 1862-6319. ; 217:4
-
Tidskriftsartikel (refereegranskat)abstract
- Silicon quantum dots (Si QDs) featuring high photoluminescence (PL) intensity are necessary for the realization of different photonic and photovoltaic devices, such as light-emitting diodes (LEDs) and luminescent solar concentrators (LSCs). Herein, Si QDs on a approximate to 100-200 nm thin silicon dioxide membrane with a metal back-coating are prepared. The dots are formed from the device layer of a silicon-on-insulator (SOI) wafer by etching and thermal oxidation. Aluminum is sputtered on the backside of the membrane, acting as a back-surface mirror, changing the local density of optical modes, as well as the local excitation field. The PL properties of such Si QDs are then characterized at the single-particle level. It is found that the PL yield of single Si QDs on the membrane is enhanced by approximately one order of magnitude, compared with that of Si QDs outside the membrane under the same excitation power. These results indicate that advances in nanofabrication can substantially improve the optical properties of Si QDs, thus paving the way for their application.
|
|
| 3. |
- Zhou, Jingjian, et al.
(författare)
-
Wafer-scale fabrication of isolated luminescent silicon quantum dots using standard CMOS technology
- 2020
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 31:50
-
Tidskriftsartikel (refereegranskat)abstract
- A wafer-scale fabrication method for isolated silicon quantum dots (Si QDs) using standard CMOS technology is presented. Reactive ion etching was performed on the device layer of a silicon-on-insulator wafer, creating nano-sized silicon islands. Subsequently, the wafer was annealed at 1100 degrees C for 1 h in an atmosphere of 5% H(2)in Ar, forming a thin oxide passivating layer due to trace amounts of oxygen. Isolated Si QDs covering large areas (similar to mm(2)) were revealed by photoluminescence (PL) measurements. The emission energies of such Si QDs can span over a broad range, from 1.3 to 2.0 eV and each dot is typically characterized by a single emission line at low temperatures. Most of the Si QDs exhibited a high degree of linear polarization along Si crystallographic directions [110] abd [(1) over bar 10]. In addition, system resolution-limited (250 mu eV) PL linewidths (full width at half maximum) were measured for several Si QDs at 10 K, with no clear correlation between emission energy and polarization. The initial part of PL decays was measured at room temperature for such oxide-embedded Si QDs, approximately several microseconds long. By providing direct access to a broad size range of isolated Si QDs on a wafer, this technique paves the way for the future fabrication of photonic structures with Si QDs, which can potentially be used as single-photon sources with a long coherence length.
|
|
