arXiv subjects

S. Oberg

Publications and source records attributed to S. Oberg.

3 recordsLinked to original sources

arXiv2013

Electronic structure modification of Si-nanocrystals with F4 -TCNQ

We use first-principles models to demonstrate how an organic oxidizing agent, F4 -TCNQ (7,7,8,8- tetracyano-2,3,5,6-tetrafluoroquinodimethane), modifies the electronic structure of silicon nanocrys- tals, suggesting it may enhance p-type carrier density and mobility. The proximity of the lowest unoccupied level of F4 -TCNQ to the highest occupied level of the Si-nanocrystals promotes the formation of an empty hybrid state overlapping both nanocrystal and molecule, reducing the exci- tation energy to about 0.8-1 eV in vacuum. Hence, it is suggested that F4 -TCNQ can serve both as a surface oxidant and a mediator for hole hopping between adjacent nanocrystals.

cond-mat.mtrl-sci↗

arXiv2012

Doping of Si nanoparticles: the effect of oxidation

The preferred location of boron and phosphorus in oxidized free-standing Si nanoparticles was investigated using a first-principles density functional approach. The calculated formation energies indicate that P should segregate to the silicon core, whereas B is equally stable in the Si and SiO_2 regions. Our models thus suggest that, in contrast with nanocrystals with H-terminated surfaces, the efficiency of phosphorus incorporation in oxidized Si nanoparticles can be improved by thermal annealing.

cond-mat.mtrl-sci↗

arXiv2007

The effect of dipole-dipole interactions between atoms in an active medium

Based on the results of numerical modeling, it is shown that dipole-dipole interactions among atoms in the active medium influences strongly the character of the associated superradiation. The main effect is to make the nuclear subsystem behave chaotically. Its strength increases with the atom density, and leads to the suppression of distant collective correlations and superradiation. Near correlations between the atoms are established, causing a confinement effect: a shielding of radiation in the active medium.

cond-mat.str-el↗