Defects in semiconductor nanostructures

Abstract

Impurities play a pivotal role in semiconductors. One part in a million of phosphorous in silicon alters the conductivity of the latter by several orders of magnitude. Indeed, the information age is possible only because of the unique role of shallow impurities in semiconductors. Although work in semiconductor nanostructures (SN) has been in progress for the past two decades, the role of impurities in them has been only sketchily studied. We outline theoretical approaches to the electronic structure of shallow impurities in SN and discuss their limitations. We find that shallow levels undergo a SHADES (SHAllow-DEep-Shallow) transition as the SN size is decreased. This occurs because of the combined effect of quantum confinement and reduced dielectric constant in SN. Level splitting is pronounced and this can perhaps be probed by ESR and ENDOR techniques. Finally, we suggest that a perusal of literature on (semiconductor) cluster calculations carried out 30 years ago would be useful.

Spectroscopic and electronic structure calculation of a potential chemotherapeutic agent 5-propyl-6-(p-tolylsulfanyl)pyrimidine-2,4(1H,3H)-dione using first principles

“…Trigonal ring bending mode is calculated at 999 cm À1 , and corresponding observed peak in the experimental spectra is at 1018 cm À1 . The CeCeC in-plane bending vibrations are generally observed around 600 cm À1 [73,74]. The observed band in FT-IR/FT-Raman spectra at 580/595, 526/528 and 436/443 cm À1 are assigned to the CeCeC in-plane bending vibrations which are in good coherence with the theoretical spectra.…”

“…3. This electronic absorption corresponds to the transition from the molecular orbital HOMO (73) to LUMO (74) in methanol solvent and is a p / p * transition. The peak in the calculated UV spectrum in gas phase arises mainly due to the electronic transition given by H/Lþ2.…”

A general penalty method for density‐to‐potential inversion

“…As is clear from the description above, in carrying out KSDFT calculations, E xc [ ρ ] functional and, consequently, its derivative v xc [ ρ ]( r ) are the only ingredients that are approximated; everything else is known exactly. Therefore, to obtain the exact v xc ( r ) for a given density, some other method has to be used; As noted earlier, knowing v xc ( r ) exactly is of interest in itself and is also important to provide insights [ 13–25 ] into the working of approximate exchange‐correlation functionals E xc [ ρ ]. To do this, several inversion schemes have been proposed.…”