Optoelectronic properties of XIn sub(2)S sub(4) (X = Cd, Mg) thiospinels through highly accurate all-electron FP-LAPW method coupled with modified approximations

• Published in: Journal of alloys and compounds 2015-03, Vol.625, p.182-187
• Main Authors: Yousaf, Masood, Dalhatu, S A, Murtaza, G, Khenata, R, Sajjad, M, Musa, A, Aliabad, HA Rahnamaye, Saeed, M A
• Format: Article
• Language: English
• Subjects: Approximation; Cadmium; Dielectrics; Electronics; Joining; Magnesium; Optoelectronic devices; Plane waves
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2014.11.104

We report the stmctural, electronic and optical properties of the thiospinels XIn sub(2)S sub(4) (X = Cd, Mg), using highly accurate all-electron full potential linearized augmented plane wave plus local orbital method. In order to calculate the exchange and correlation energies, the method is coupled with modified techniques such as GGA+U and mBJ-GGA, which yield improved results as compared to the previous studies. GGA+SOC approximation is also used for the first time on these compounds to examine the spin orbit coupling effect on the band structure. From the analysis of the structural parameters, robust character is predicted for both materials. Energy band structures profiles are fairly the same for GGA, GGA+SOC, GGA+U and mBJ-GGA, confirming the indirect and direct band gap nature of CdIn sub(2)S sub(4) and MgIn sub(2)S sub(4) materials, respectively. We report the trend of band gap results as: (mBJ-GGA) > (GGA+U) > (GGA) > (GGA+ SOC). Localized regions appearing in the valence bands for CdIn sub(2)S sub(4) tend to split up nearly by approximately 1 eV in the case of GGA+SOC. Many new physical parameters are reported that can be important for the fabrication of optoelectronic devices. Optical spectra namely, dielectric function (DF), refractive index n( omega ), extinction coefficient k( omega ), reflectivity R( omega ), optical conductivity [sigma]( omega ), absorption coefficient alpha ( omega ) and electron loss function are discussed. Optical's absorption edge is noted to be 1.401 and 1.782 for CdIn sub(2) S sub(4) and MgIn sub(2)S sub(4), respectively. The prominent peaks in the electron energy spectrum situated between 15 eV and 23 eV for the herein studied materials indicate a transition from metallic to the dielectric character.