The combination of electrical conductivity, chemical and metallurgical stability, refractory character, having lattice constants that are close to those of III-nitrides makes transition metal nitrides promising candidates for electronics and device applications. We study the structure, stability, and the plasma energy of stoichiometric, transition metal nitrides of similar crystal quality as well as the widest variety of their ternaries ever reported. We establish the phase spaces of the plasma energy (6.9–10.5 eV) and the work function (3.7–5.1 eV) of these complex nitrides with their lattice constant (0.416–0.469 nm) and we investigate the limits of their applications.
We report on the electronic structure and optical properties of conducting ternary transition metal nitrides consisting of metals of different groups of the periodic table of elements. For the study of the bonding, electronic structure, and optical properties of conducting TixTa1−xN film growth, optical spectroscopy and ab initio calculations were used. Despite the different valence electron configuration of the constituent elements, Ta(d3s2) and Ti(d2s2), we show that TiN and TaN are completely soluble due to the hybridization of the d and sp electrons of the metals and N, respectively, that stabilizes the ternary TixTa1−xN systems to the rocksalt structure. The optical properties of TixTa1−xN have been studied using spectroscopic methods and detailed electronic structure calculations, revealing that the plasma energy of the fully dense TixTa1−xN is varying between 7.8 and 9.45 eV. Additional optical absorption bands are manifested due to the N p→Ti/Ta d interband transition the t2g→eg transition due to splitting of the metals’ d band, with the major exception of the Ti0.50Ta0.50N, where the eg unoccupied states are not manifested due to the local structure of the ternary system; this finding is observed for the first time and proves previous assignments of optical transitions in TaN.
We present results on the stability and tailoring of the cell size of conducting δ-TixTa1−xN obtained by film growth and ab initio calculations. Despite the limited solubility of Ta in Ti, we show that TiN and TaN are soluble due to the hybrization of the d and sp electrons of the metal and N, respectively, that stabilizes the ternary system to the rocksalt structure. The stress-free cell sizes follow the Vegard’s rule; nevertheless, process-dependent stresses expand the cell size of the as-grown films. The electronic properties of δ-TixTa1−xN films (ρ=180Ωcm) are similar to those of TiN and TaN.
Articles you may be interested inComparative analysis of electronic structure and optical properties of crystalline and amorphous silicon nitrides Tantalum nitride is an interesting solid with exceptional properties and it might be considered as a representative model system of the d 3 s 2 transition metal nitrides. In this work highly textured, stoichiometric, rocksalt TaN͑111͒ films have been grown on Si͑100͒ by pulsed laser deposition. The films were under a triaxial stress, which has been determined by the sin 2 method. The stress-free lattice parameter was found to be 0.433Ϯ 0.001 nm, a value which has been also determined by ab initio calculations within the local spin density approximation. The optical properties of TaN have been studied using spectroscopic ellipsometry and detailed band structure calculations. The electron conductivity of TaN is due to the Ta 5dt 2g band that intercepts the Fermi level and is the source of intraband absorption. The plasma energies of fully dense rocksalt TaN were found to be 9.45 and 9.7 eV based on the experimental results and ab initio calculations, respectively. Additional optical absorption bands were also observed around 1.9 and 7.3 eV and attributed to be due to crystal field splitting of the Ta 5d band ͑t 2g → e g transition͒ and the N p → Ta d interband transition, respectively.
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