[Paper Review] First-principles calculations of Sc2CdS4 and Y2CdS4 compounds

Abdul Ahad Khan, Zubaida Noor+1 more|arXiv (Cornell University)|Aug 9, 2018

Chalcogenide Semiconductor Thin Films24 references4 citations

TL;DR

This study investigates Sc2CdS4 and Y2CdS4 compounds using first-principles density functional theory calculations, revealing both materials exhibit direct band gaps of 1.886 eV and 2.209 eV, respectively, with strong S-p and Sc/Y-d orbital hybridization enhancing electrical transport. The compounds show high optical and thermal responses, indicating strong potential for optoelectronic and thermoelectric applications as P-type materials with dominant hole conduction.

ABSTRACT

Direct energy bandgap materials are crucial for the efficient optoelectronics devices. Therefore, the investigation of new direct gap materials is important. In the present work, two novel d-metal sulfides Sc2CdS4 and Y2CdS4 compounds are investigated by using the all electron full potential linearized augment plane wave method. Both the compounds show semiconducting nature and direct band gap with a value 1.886eV for Sc2CdS4 and 2.209eV for Y2CdS4, respectively. Strong hybridization between S-p and Sc/Y-d orbitals present among valence and conduction bands which is beneicial to electrical transport. Key optical parameters are calculated. The static value of the reflectivity R(0) and refractive index n(0) are vary inversely with the energy band gap (Eg). Both the compounds Sc2CdS4 and Y2CdS4 are P-type thermoelectric materials because the Hole carriers dominate the electronic transport. High optical and thermal response for all compounds reveals that they are potential candidates for optical and thermoelectric devices.

Motivation & Objective

• To explore new direct band gap semiconductors for efficient optoelectronic applications.
• To investigate the electronic and optical properties of novel d-metal sulfides Sc2CdS4 and Y2CdS4.
• To evaluate the thermoelectric potential of these compounds by analyzing carrier dominance and transport behavior.
• To determine the relationship between band gap energy and optical response parameters such as reflectivity and refractive index.

Proposed method

• All-electron full potential linearized augmented plane wave (FP-LAPW) method was employed for electronic structure calculations.
• Density functional theory (DFT) with the generalized gradient approximation (GGA) was used to compute ground-state properties.
• Electronic band structures and density of states were calculated to analyze orbital hybridization and band gap nature.
• Optical parameters including static reflectivity R(0) and refractive index n(0) were computed from the dielectric function.
• Carrier effective mass and transport behavior were analyzed to assess thermoelectric performance.
• The energy band gap was calculated using the PBE functional, with spin-orbit coupling neglected.

Experimental results

Research questions

• RQ1 Do Sc2CdS4 and Y2CdS4 exhibit direct band gaps suitable for optoelectronic applications?
• RQ2 What is the degree and nature of orbital hybridization between S-p and transition metal d-orbitals in these compounds?
• RQ3 How do the optical properties such as reflectivity and refractive index correlate with the band gap energy?
• RQ4 Are these materials suitable for thermoelectric applications, and what type of charge carriers dominate transport?
• RQ5 What is the relationship between the band gap and the static optical response parameters R(0) and n(0)?

Key findings

• Sc2CdS4 exhibits a direct band gap of 1.886 eV, while Y2CdS4 has a larger direct band gap of 2.209 eV.
• Strong hybridization between S-p and Sc/Y-d orbitals is observed in both compounds, enhancing electrical transport properties.
• The static reflectivity R(0) and refractive index n(0) vary inversely with the band gap energy, indicating tunable optical response.
• Both compounds display P-type character, with hole carriers dominating electronic transport, indicating thermoelectric potential.
• High optical and thermal responses suggest strong suitability for use in optical and thermoelectric devices.
• The calculated optical parameters confirm that these materials are promising candidates for visible-light optoelectronic applications.