| 1. |
|
|
| 2. |
- Pettersson, Håkan, et al.
(författare)
-
Photoexcitation of excitons in self-assembled quantum dots
- 2004
-
Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 85:21, s. 5046-5048
-
Tidskriftsartikel (refereegranskat)abstract
- Using an approach of combining Fourier transform infrared spectroscopy with resonant illumination from a secondary external light source, we have measured the photocurrent (PC) for multiple layers of self-assembled InAs dots embedded in a matrix of InP. Without external illumination, we observe photoexcitation of electrons from bound states in the dots to the InP barrier. By additional illumination from the external light source, a strong broadening of the PC signal is observed. We interpret this broadening in terms of photoexcitation of electrons in the presence of additional holes in the dots created by the external light source. We extract the spectral distribution of the photoexcitation process at 6 and 77 K, respectively, and show by comparison with theoretical calculations that it is consistent with an exciton binding energy of 20 meV.
|
|
| 3. |
- Bylander, Jonas, 1978, et al.
(författare)
-
Interference and correlation of two independent photons
- 2003
-
Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6079 .- 1434-6060. ; 22, s. 295-301
-
Tidskriftsartikel (refereegranskat)abstract
- Two independent photons, produced through the spontaneous emission of two separate emitters subject to uncorrelated dephasing processes, can display two-photon interference (i.e. coalescence into a two-photon state) when they are incident simultaneously on a beamsplitter, in a manner analogous to that of twin photons produced through degenerate parametric fluorescence. The presence of dephasing processes, however, reduces the interference contrast (i.e. the probability of coalescence), by the ratio of the coherence time to the lifetime of the emitter.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Andersson, M, et al.
(författare)
-
Macroscopic alignment of silver nanoparticles in reverse hexagonal liquid crystalline templates
- 2002
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 2:12, s. 1403-1407
-
Tidskriftsartikel (refereegranskat)abstract
- A flexible method of preparing and macroscopically aligning nanoparticles of crystalline silver into millimeter long fibers is presented. The approach utilizes the dual functionality of a reverse hexagonal liquid crystalline template containing a built-in reducing agent facing the aqueous domain. The method is advantageous in that its slow kinetics allows for a thorough introduction of a silver salt into the liquid crystal before the reduction takes place, allowing for an efficient loading of he template and a retained mesoscopic ordering as evidenced by SAXS. It was confirmed by H-1 NMR that the oxyethylene groups of the amphiphilic polymer reduce the silver ions while being oxidized to aldehydes. The silver nanoparticles are uniform in size and in the same size range as the diameter of the aqueous domain of the liquid crystal (3 nm), further supporting that the silver particles form inside the liquid crystal. TEM images confirm the macroscopic alignment of silver nanoparticles into fibrils and the packing of fibrils into millimeter long fibers. The diameter of the fibrils and fibers ranges from 30 nm to several hundreds of micrometers. Electron diffraction analysis of a collection of silver nanoparticles confirms their crystallinity as three diffraction rings could be indexed to the face centered cubic structure of silver. A key to the successful macroscopic alignment of the nanoparticles is that the particles are formed inside the liquid crystal, thus minimizing the need for their diffusion i to and inside the liquid crystal.
|
|
| 8. |
- Balmes, Olivier, et al.
(författare)
-
Cryo-TEM observation of 3-dimensionally ordered aggregates of 5-nm gold particles in organic solvents
- 2004
-
Ingår i: Journal of Nanoparticle Research. - : Springer Science and Business Media LLC. - 1572-896X .- 1388-0764. ; 6:6, s. 569-576
-
Tidskriftsartikel (refereegranskat)abstract
- In this article, we show evidence for the assembly of ordered 3-dimensional aggregates of 5-nm gold particles in toluene, 1-octanol, n-decane, and chloroform. The use of plunge-freezing allows to freeze the solution containing the aggregates at a rate which does not allow reorganisation of the particles during sample preparation. The samples were then observed using cryo-transmission electron microscopy (cryo-TEM) showing that most of the particles were part of ordered aggregates, thus proving that organisation already exists in solution. In some cases, the stability of the sample under the electron beam made it possible to record several pictures of the same aggregate at different angles and build animated tilt series.
|
|
| 9. |
- Björk, Mikael, et al.
(författare)
-
Few-electron quantum dots in nanowires
- 2004
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 4:9, s. 1621-1625
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate transport spectroscopy on bottom-up grown few-electron quantum dots in semiconductor nanowires. The dots are defined by InP double barrier heterostructures in InAs nanowires catalytically grown from nanoparticles. By changing the dot size, we can design devices ranging from single-electron transistors to few-electron quantum dots. In the latter case, electrons can be added one by one to the dots from 0 to similar to50 electrons while maintaining an almost constant charging energy, with addition spectra of the devices displaying shell structures as a result of spin and orbital degeneracies. The reduced dimensionality of the nanowire emitter gives rise to pronounced resonant tunneling peaks, where a gate can be used to control the peak positions.
|
|
| 10. |
- Björk, Mikael, et al.
(författare)
-
One-dimensional steeplechase for electrons realized
- 2002
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 2:2, s. 87-89
-
Tidskriftsartikel (refereegranskat)abstract
- We report growth of one-dimensional semiconductor nanocrystals, nanowhiskers, in which segments of the whisker with different composition are formed, illustrated by InAs whiskers containing segments of InP. Our conditions for growth allow the formation of abrupt interfaces and heterostructure barriers of thickness from a few monolayers to 100s of nanometers, thus creating a one-dimensional landscape along which the electrons move. The crystalline perfection, the quality of the interfaces, and the variation in the lattice constant are demonstrated by high-resolution transmission electron microscopy, and the conduction band off-set of 0.6 eV is deduced from the current due to thermal excitation of electrons over an InP barrier.
|
|
