Electronic, magnetic, optical and transport properties of wurtzite-GaN doped with rare earth (RE= Pm, Sm, and Eu): First principles approach

Rare earth (RE)-doped GaN nanowires (NWs), combining the well-defined and controllable optical emission lines of trivalent RE ions with the high crystalline quality, versatility, and small dimension of the NW host, are promising building blocks for future nanoscale devices in optoelectronics and quantum technologies. Europium doping of GaN NWs was performed by ion implantation, and structural and optical properties were assessed in comparison to thin film reference samples. Despite some surface degradation for high implantation fluences, the NW core remains of high crystalline quality with lower concentrations of extended defects than observed in ion-implanted thin films. Strain introduced by implantation defects is efficiently relaxed in NWs and the measured deformation stays much below that in thin films implanted in the same conditions. Optical activation is achieved for all samples after annealing, and while optical centers are similar in all samples, Eu3+ emission from NW samples is shown to be less ...

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Incorporation of Europium into GaN Nanowires by Ion Implantation

The structural stability and magnetic properties of a grain boundary (GB) formed by aligning two ZnO single crystals oriented at an angle of 45° is investigated by density functional theory, using generalized gradient approximation (GGA) and taking the U parameter into consideration for the 4f impurity states. We found that the GB is stable with no dangling bonds and inter-granular structures. The stability of defects such as Gd substituted to the Zn site (GdZn), Zn vacancy (VZn) and O vacancy (VO) as well as defect complexes GdZn–GdZn, GdZn–VZn, and GdZn–VO are analyzed using formation energy calculations. It is found that GdZn–GdZn clusters prefers to form at the GB. The spin polarization at the GdZn sites is too localized and the exchange coupling energy is insufficient to overcome the thermal fluctuations. However, we show that the presence of VZn increases the hybridization between p orbitals of O as well as d orbitals of Zn, which can assist in increasing the magnetic polarization of the system. This work advances the understanding of the ferromagnetism in Gd-doped ZnO, indicating that Gd clustering at the GB is not likely to contribute to the ferromagnetism.

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Analysis on the energetics, magnetism and electronic properties in a 45° ZnO grain boundary doped with Gd

Ab initio study of hydrogen sensing in Pd and Pt functionalized GaN [0 0 0 1] nanowires

Improved H2 detection performance of GaN sensor with Pt/Sulfide treatment of porous active layer prepared by metal electroless etching

Present work investigates the structural, electronic and magnetic properties of wurtzite (0001) GaN nanowires (NWs) doped with Gd and point defects by employing the GGA+U approximation. We find that Ga vacancies (VGa) exhibit lower formation energy compared to N vacancies (VN). Further stabilization of point defects occurs due to the presence of Gd and ambient ferromagnetism (FM) can be stabilized in the NW by the additional positive charge induced by the VGa. Electronic structure analysis shows that VGa introduces additional levels in the band gap leading to ferromagnetic coupling due to the hybridization of the p states of the Ga and N atoms with the Gd d and f states. Ferromagnetic exchange coupling energy of 76.4meV is obtained in presence of Gd-VGa complex, and hence the FM is largely determined by the cation vacancy-rare earth complex defects in GaN NWs. On the other hand, the VN, which introduce additional electron carriers, does not assist in increasing the ferromagnetic exchange energy.

Assa Aravindh S

Papers

Defect-impurity complex induced long-range ferromagnetism in GaN nanowires