Ab initio calculations on Eu doped (GaN)n (n-=-12, 13, and 32) nanoparticles show that Eu doping in nanoparticles is favorable compared with bulk GaN as a large fraction of atoms lie on the surface where strain can be released compared with bulk where often Eu doping is associated with a N vacancy. Co-doping of Si further facilitates Eu doping as strain from an oversized Eu atom and an undersized Si atom is compensated. These results along with low symmetry sites in nanoparticles make them attractive for developing strongly luminescent nanomaterials. The atomic and electronic structures are discussed using generalized gradient approximation (GGA) for the exchange-correlation energy as well as GGA + U formalism. In all cases of Eu (Eu-+-Si) doping, the magnetic moments are localized on the Eu site with a large value of 6μB (7μB). Our results suggest that co-doping can be a very useful way to achieve rare-earth doping in different hosts for optoelectronic materials. © 2015 AIP Publishing LLC.

Vijay Kumar

Center for Informatics

Kaur P.

Sekhon S.S.

Zavada J.M.

Fulltext

<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

Enhanced stability of Eu in GaN nanoparticles: Effects of Si co-doping

Journal of Applied Physics

Results of ab initio pseudopotential calculations are presented concerning the atomic structure and magnetic properties of GaN doped with selected rare earth atoms. Effects of codoping these materials with Si are also discussed. It has been found that the doping of a Eu atom on a Ga site in bulk GaN creates significant local deformation and it costs 1.84eV. However, the addition of a Si atom makes Eu doping in bulk GaN energetically favorable as strain from an oversized Eu atom and an undersized Si atom is compensated. Therefore codoping of Si facilitates doping of rare earths in GaN. The excess charge due to codoping of Si tends to cause Eu to be in a 2+ state and the magnetic moment on Eu ion is enhanced to 7μB. Further studies have shown that Eu atoms tend to cluster with interatomic separation of about 5Å and there is ferromagnetic coupling. For rare earth atoms in nanoparticles, ab initio calculations have been performed on (GaN)n (n=12, 16, 22, and 32) nanoclusters with Eu, Gd, and Nd atoms substituting on Ga sites. These studies have yielded preferred atomic structures and magnetic behavior. Cage structures of these GaN nanoclusters were found to be lower in energy as compared to bulk fragments. Specific results show that Eu-doping in GaN nanoparticles is favorable compared with bulk GaN since a large fraction of atoms in a nanocluster lie on the surface where strain can be lower. Codoping of Si further facilitates Eu doping as in the case of bulk GaN. © 2016 Elsevier Ltd. All rights reserved.

Rare Earth and Transition Metal Doping of Semiconductor Materials: Synthesis, Magnetic Properties and Room Temperature Spintronics

Energetics, atomic structure, and magnetics of rare earth-doped GaN bulk and nanoparticles

Optical Materials

Crystal field analysis of rare-earth ions energy levels in GaN

The role of donor-acceptor pairs in the excitation of Eu-ions in GaN:Eu epitaxial layers

Japanese Journal of Applied Physics

Present understanding of Eu luminescent centers in Eu-doped GaN grown by organometallic vapor phase epitaxy

physica status solidi (c)

Europium-doped GaN(Mg): beyond the limits of the light-emitting diode

The Journal of Chemical Physics

Correlation between the variation in observed melting temperatures and structural motifs of the global minima of gallium clusters: An ab initio study