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

01 Jan 2016-pp 103-126

TL;DR: In this paper, the atomic structure and magnetic properties of GaN doped with selected rare earth atoms were investigated and the effects of codoping these materials with Si are also discussed, and 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 1.84 eV.

Abstract: 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 1.84 eV. 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 7 μB. Further studies have shown that Eu atoms tend to cluster with interatomic separation of about 5 A 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.

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01 Mar 2002

TL;DR: High quality thin films of the ferromagnetic semiconductor EuO have been prepared and were studied using a new form of spin-resolved spectroscopy, finding that large changes in the electronic structure across the Curie and metal-insulator transition temperature are caused by the exchange splitting of the conduction band.

Abstract: High quality thin films of the ferromagnetic semiconductor EuO have been prepared and were studied using a new form of spin-resolved spectroscopy. We observed large changes in the electronic structure across the Curie and metal-insulator transition temperature. We found that these are caused by the exchange splitting of the conduction band in the ferromagnetic state, which is as large as 0.6 eV. We also present strong evidence that the bottom of the conduction band consists mainly of majority spins. This implies that doped charge carriers in EuO are practically fully spin polarized.

162 citations

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01 Feb 2023

TL;DR: A brief overview of the different types of dilute magnetic semiconductors available and the mechanism of their operation have been discussed in this article , and some important applications arising out of the novel and exciting properties of the DMS materials have also been discussed.

Abstract: While there are immense possibilities from integration of electric and magnetic properties of materials in magnetic semiconductors, fine tuning the synthesis processes for the fabrication of magnetic materials that can exhibit magnetism even at high temperatures have been of particular interest and has also been a significant challenge for dilute magnetic semiconductors (DMS) synthesis. A brief overview of the different types of DMS materials available and the mechanism of their operation have been discussed in this review article. Furthermore, some important applications arising out of the novel and exciting properties of the DMS materials have also been discussed.

1 citations

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01 Jan 2022

TL;DR: In this paper , different types of rare earth (RE)-doped semiconductors are reviewed and then the common synthetic method and applications of each category are discussed, and different synthetic techniques for each material are discussed in detail.

Abstract: Doping different materials, especially semiconductors, has been known as a powerful tool for improving properties and finding excellent applications in industry. Applications of doping in semiconductor industry especially in nanoelectronics and nanophotonics is a growing field of research. Lanthanide rare earth (RE) have been extensively used in different types of semiconductors as trace additives with extraordinary photonic, magnetic, photocatalytic, and photovoltaic properties. In this chapter, different types of RE-doped semiconductors will be reviewed and then the common synthetic method and applications of each category will be discussed. It will cover a wide range of doped semiconductors from the conventional Si and III-N materials for photonic applications to TiO2 and ZnO photocatalysts and perovskites for photovoltaic applications. Moreover, different synthetic techniques for each material will be discussed in detail.

1 citations

##### References

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IBM

^{1}TL;DR: An approach for electronic structure calculations is described that generalizes both the pseudopotential method and the linear augmented-plane-wave (LAPW) method in a natural way and can be used to treat first-row and transition-metal elements with affordable effort and provides access to the full wave function.

Abstract: An approach for electronic structure calculations is described that generalizes both the pseudopotential method and the linear augmented-plane-wave (LAPW) method in a natural way. The method allows high-quality first-principles molecular-dynamics calculations to be performed using the original fictitious Lagrangian approach of Car and Parrinello. Like the LAPW method it can be used to treat first-row and transition-metal elements with affordable effort and provides access to the full wave function. The augmentation procedure is generalized in that partial-wave expansions are not determined by the value and the derivative of the envelope function at some muffin-tin radius, but rather by the overlap with localized projector functions. The pseudopotential approach based on generalized separable pseudopotentials can be regained by a simple approximation.

48,474 citations

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TL;DR: In this paper, the formal relationship between US Vanderbilt-type pseudopotentials and Blochl's projector augmented wave (PAW) method is derived and the Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional.

Abstract: The formal relationship between ultrasoft (US) Vanderbilt-type pseudopotentials and Bl\"ochl's projector augmented wave (PAW) method is derived. It is shown that the total energy functional for US pseudopotentials can be obtained by linearization of two terms in a slightly modified PAW total energy functional. The Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional. A simple way to implement the PAW method in existing plane-wave codes supporting US pseudopotentials is pointed out. In addition, critical tests are presented to compare the accuracy and efficiency of the PAW and the US pseudopotential method with relaxed core all electron methods. These tests include small molecules $({\mathrm{H}}_{2}{,\mathrm{}\mathrm{H}}_{2}{\mathrm{O},\mathrm{}\mathrm{Li}}_{2}{,\mathrm{}\mathrm{N}}_{2}{,\mathrm{}\mathrm{F}}_{2}{,\mathrm{}\mathrm{BF}}_{3}{,\mathrm{}\mathrm{SiF}}_{4})$ and several bulk systems (diamond, Si, V, Li, Ca, ${\mathrm{CaF}}_{2},$ Fe, Co, Ni). Particular attention is paid to the bulk properties and magnetic energies of Fe, Co, and Ni.

46,297 citations

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TL;DR: In this article, a method for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector is given, where the integration can be over the entire zone or over specified portions thereof.

Abstract: A method is given for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector. The integration can be over the entire Brillouin zone or over specified portions thereof. This method also has applications in spectral and density-of-state calculations. The relationships to the Chadi-Cohen and Gilat-Raubenheimer methods are indicated.

42,677 citations

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TL;DR: A way is found to visualize and understand the nonlocality of exchange and correlation, its origins, and its physical effects as well as significant interconfigurational and interterm errors remain.

Abstract: Generalized gradient approximations (GGA's) seek to improve upon the accuracy of the local-spin-density (LSD) approximation in electronic-structure calculations. Perdew and Wang have developed a GGA based on real-space cutoff of the spurious long-range components of the second-order gradient expansion for the exchange-correlation hole. We have found that this density functional performs well in numerical tests for a variety of systems: (1) Total energies of 30 atoms are highly accurate. (2) Ionization energies and electron affinities are improved in a statistical sense, although significant interconfigurational and interterm errors remain. (3) Accurate atomization energies are found for seven hydrocarbon molecules, with a rms error per bond of 0.1 eV, compared with 0.7 eV for the LSD approximation and 2.4 eV for the Hartree-Fock approximation. (4) For atoms and molecules, there is a cancellation of error between density functionals for exchange and correlation, which is most striking whenever the Hartree-Fock result is furthest from experiment. (5) The surprising LSD underestimation of the lattice constants of Li and Na by 3--4 % is corrected, and the magnetic ground state of solid Fe is restored. (6) The work function, surface energy (neglecting the long-range contribution), and curvature energy of a metallic surface are all slightly reduced in comparison with LSD. Taking account of the positive long-range contribution, we find surface and curvature energies in good agreement with experimental or exact values. Finally, a way is found to visualize and understand the nonlocality of exchange and correlation, its origins, and its physical effects.

16,870 citations

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TL;DR: Zener's model of ferromagnetism, originally proposed for transition metals in 1950, can explain T(C) of Ga(1-)(x)Mn(x)As and that of its II-VI counterpart Zn(1)-Mn (x)Te and is used to predict materials with T (C) exceeding room temperature, an important step toward semiconductor electronics that use both charge and spin.

Abstract: Ferromagnetism in manganese compound semiconductors not only opens prospects for tailoring magnetic and spin-related phenomena in semiconductors with a precision specific to III-V compounds but also addresses a question about the origin of the magnetic interactions that lead to a Curie temperature (T(C)) as high as 110 K for a manganese concentration of just 5%. Zener's model of ferromagnetism, originally proposed for transition metals in 1950, can explain T(C) of Ga(1-)(x)Mn(x)As and that of its II-VI counterpart Zn(1-)(x)Mn(x)Te and is used to predict materials with T(C) exceeding room temperature, an important step toward semiconductor electronics that use both charge and spin.

6,798 citations

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