Identification of a N-related shallow acceptor and electron paramagnetic resonance center in ZnO: N2+on the Zn site

Abstract

First-principles calculations of N 2 in ZnO located on the Zn site show that this defect is a shallow double acceptor and can be identified with a N-related shallow level observed experimentally by donor-acceptor-pair recombination. When the shallow acceptor level is occupied with a single electron, it can also explain a N 2 -related electron paramagnetic resonance signal observed in ZnO. We show that the g factor and hyperfine structure observed for this center are closer to those of a N 2 + radical than to a N − 2 radical as previously proposed in literature and hence consistent with the Zn location.

Molecular nitrogen acceptors in ZnO nanowires induced by nitrogen plasma annealing

“…The enhancement of the DAP intensity is not associated with the overall nitrogen content, which remains almost unchanged for anneals longer than 30 min. The direct correlation between the P 2 and I(3.232 eV) strongly indicates the involvement of loosely bound N 2 in the DAP transition and supports the N 2 acceptor model [13,28], in which N 2 at a Zn site is weakly bound to the lattice and retains most of its molecular characteristics. Atomic N at the O site or its complexes have been theoretically predicted to be the shallow acceptor [10,12]; however, this possibility can be ruled out for ZnO nanowires.…”

“…Nitrogen atoms are more readily incorporated into the nanowires than their molecular counterparts and initially incorporated substitutionally at O sites. Given the small nanowire diameters, N atoms will diffuse throughout the entire nanowire volume, whereas gaseous nitrogen adsorbs onto the nanowire surface and then desorbs from the sample by prolonged plasma annealing [13]. As seen in Fig.…”

“…This complex is preferentially formed on the Zn-terminated surface during ZnO growth, but the transition of N Zn -V O to N O -V Zn must overcome a large energy barrier of 1.1 eV. More recently, it has been predicted that N 2 molecule could be accommodated at a Zn site [13]. By comparing the first principles calculation results and the ESR spectra of N-doped ZnO, Lambrecht and Boonchun [13] concluded that (N 2 ) Zn is the shallow double acceptor responsible for the DAP transition.…”

“…More recently, it has been predicted that N 2 molecule could be accommodated at a Zn site [13]. By comparing the first principles calculation results and the ESR spectra of N-doped ZnO, Lambrecht and Boonchun [13] concluded that (N 2 ) Zn is the shallow double acceptor responsible for the DAP transition. To our knowledge, to date, no experimental study has examined the interrelationships between the chemical states of nitrogen dopants and the optical signatures of shallow acceptors.…”

Recharging behavior of nitrogen-centers in ZnO

“…However, performing model calculations for such species the results for their recharging properties (being donor or acceptor) and the energy position of the recharging levels were strongly depending on the theoretical method used. 5 Nickel et al calculated that N 2 causes localized states in the band gap either by forming an N 2 O molecule or by breaking a Zn-O bond. 6 The latter was calculated to have a level about 170 meV above the valence band.…”