Abstract
Using first principles total-energy calculations within the framework of density functional theory, the relative stability and the structural and electronic properties of a VN/GaN/VN interlayer in sodium chloride (NaCl), cesium chloride (CsCl), nickel arsenide (NiAs), zinc-blende, and wurtzite structures were studied. The calculations were carried out using a method based on pseudopotential, employed exactly as implemented in Quantum-ESPRESSO code. From total energy minimization, it was found out that the global energy minimum of VN/GaN/VN is obtained for the wurtzite structure. Additionally, at high pressure, our calculations show the possibility of phase transition from the wurtzite to the NaCl structure. For the wurtzite phase, the density of states analyses revealed that the interlayer exhibits a half-metallic behavior with a magnetic moment of 2.0 µβ/V-atom. This property essentially comes from the polarization of states V-d and N-p crossing of the Fermi level. Due this property, the interlayer can potentially be used in the field of spintronics as spin injectors. Key words: Density functional theory (DFT), interlayers, structural and electronic properties.
Highlights
The group III nitrides such as gallium nitride (GaN) have been the subject of many intense investigations in the last years
To determine the structural properties in the ground state, such as the lattice constant (a), the bulk modulus (B0), the c/a ratio, and the total energy (E0) of the VN/GaN/VN interlayer in the cesium chloride (CsCl), NaCl, nickel arsenide (NiAs), zinc-blende, and wurtzite structures, the total energy was calculated as a function of the volume, and the results were fit to the Murnaghan equation of state
Since the calculations are in ground state (T = 0 degree K), the last term of the Gibbs energy can be neglected, and by working with the enthalpy, the Gibbs free energy reduces to H = U + PV (Mancera et al, 2004; Espitia et al, 2015b). This equation was used for the five crystal structures considered in this paper; the possible existence of other stable or metastable structures for a VN/GaN/VN interlayer cannot be excluded
Summary
The group III nitrides such as gallium nitride (GaN) have been the subject of many intense investigations in the last years. This interest is partly motivated by their promising applications for optical devices (Nakamura, 1997) and in high-voltage, high-power, and high-temperature microwave applications (Wagner and Bechstedt, 2002; Nakamura et al, 1994). They are wide-band-gap semiconductors and are used for short-wavelength electroluminescent devices.
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