Density functional theory analysis of electronic structure and optical properties of La doped Cd ₂ SnO ₄ transparent conducting oxide

Abstract

The electronic structural, effective masses of carriers, and optical properties of pure and La-doped Cd 2 SnO 4 are calculated by using the first-principles method based on the density functional theory. Using the GGA+U method, we show that Cd 2 SnO 4 is a direct band-gap semiconductor with a band gap of 2.216 eV, the band gap decreases to 2.02 eV and the Fermi energy level moves to the conduction band after La doping. The density of states of Cd 2 SnO 4 shows that the bottom of the conduction band is composed of Cd 5s, Sn 5s, and Sn 5p orbits, the top of the valence band is composed of Cd 4d and O 2p, and the La 5d orbital is hybridized with the O 2p orbital, which plays a key role at the conduction band bottom after La doping. The effective masses at the conduction band bottom of pure and La-doped Cd 2 SnO 4 are 0.18m 0 and 0.092m 0 , respectively, which indicates that the electrical conductivity of Cd 2 SnO 4 after La doping is improved. The calculated optical properties show that the optical transmittance of La-doped Cd 2 SnO 4 is 92%, the optical absorption edge is slightly blue shifted, and the optical band gap is increased to 3.263 eV. All the results indicate that the conductivity and optical transmittance of Cd 2 SnO 4 can be improved by doping La.

Improved electrical and optical properties in epitaxial Cd2SnO4 films

“…The curve presents that the bottom of the conduction band is placed at the point G in the Brillouin zone, as well as the top of the valence band is also at this position, revealing that the Cd 2 SnO 4 is a direct bandgap semiconductor according to atomic orbital distribution. Similar results about the Cd 2 SnO 4 films were reported by other workers 53 . The effective mass of an electron ( m * ) can be evaluated from the dispersion curve based on the second derivatives, and the standard definition of m * is …”

“…Similar results about the Cd 2 SnO 4 films were reported by other workers. 53 The effective mass of an electron (m * ) can be evaluated from the dispersion curve based on the second derivatives, and the standard definition of m * is…”