First principle investigation and substrate temperature dependent structural and electrical transport characterizations of pulsed laser deposited (PLD) cadmium indium Selenide (α-CdIn2Se4) ternary semiconducting compound thin films

Abstract

The theoretical investigations on CdIn2Se4, a ternary semiconducting compound belonging to the II-III2-VI4 family, were accomplished using the SIESTA code. Using density functional theory, the band structure of the CdIn₂Se₄ was proposed. Its semiconducting nature was highlighted by the direct band gap of ≃1.6700 eV. The values of the Fermi energy, the highest occupied molecular orbital, the lowest unoccupied molecular orbital, and Mulliken atomic charges of individual atoms in CdIn₂Se₄ were inferred. A pulsed laser deposition technique deposited CdIn2Se4 thin films on various substrates at different substrate temperatures (Ts). Electron microscopy and an X-ray diffractometer were used to study the morphology and/or crystal structure of CdIn2Se4 films. The CdIn2Se4 films were found to be amorphous when synthesized at lower Ts (< 425 K), single-phase-polycrystalline-stoichiometric when synthesized between 425 K ≤ Ts < 675 K, and polyphase when synthesized at higher Ts (> 550 K). The additional reflection observed in CdIn2Se4 films at higher Ts (> 550 K) is identified due to the characteristic peak of the hexagonal β-phase In2Se3. The ICDD card 01-089-2388 was used to index the electron diffraction and X-ray diffraction results of the tetragonally structured and P-42 m (1 1 1) crystallographic space group α-phase CdIn2Se4 films. The lattice constant and unit cell volume for the (1 1 1) reflection of CdIn2Se4 films have been inferred. For the most substantial (1 1 1) reflection, the stacking fault (5.7992 × 10−3) and unity value of the texture coefficient for the CdIn2Se4 film are extracted. No element/s other than Cd, In, and Se are evident in the CdIn2Se4 thin films’ energy dispersive analysis of X-ray spectra, which revealed the purity of the CdIn2Se4 films. The Raman investigation demonstrates the effective formation of nanocrystalline, strain-influenced CdIn2Se4 films with a prominent Raman mode at 137 cm−1. The DC electrical resistivity, thermal activation energies, band gap energies, Hall coefficient, carrier concentration, and Hall mobility were deduced for CdIn2Se4 films. The implications are addressed.