We present an evaluation of the hardness and Young’s modulus properties of medium pressure sputtered molybdenum disulfide (MoS 2 ) thin films by applying nano-indentation with continuous stiffness method combined with microstructure analysis using small angle x-ray diffraction, Raman, and an electron microscope in scanning and transmission mode. Our results indicate a vertical growth of MoS 2 crystallites with stacking values of 7-laminates along the [0 0 1] direction and an average height of 105 nm, principal Raman vibrations at at 378 cm −1 and A 1g at 407 cm −1 and an interplanar distance of ~0.62 nm as confirmed by high-resolution transmission electron microscopy. An average hardness of H = 10.5 ± 0.1 GPa and elastic modulus of E = 136 ± 2 GPa from 0 to 90 nm of indenter penetration were found in these investigations.
Using a combination of experimental techniques and density functional theory (DFT) calculations, the influence of lithium insertion on the electronic and electrochemical properties of fluorine-doped SnO2 (FTO) is assessed. For this purpose, we investigate the electrochromic behavior of a commercial FTO electrode embedded in a solution of lithium perclorate (LiClO4). The electrochromic properties are evaluated by UV–vis spectroscopy, cyclic voltammetry, and chronoamperometry. These tests show that FTO exhibits electrochromism with a respectable coloration efficiency (η = 47.9 cm2/C at 637 nm). DFT study indicates that lithium remains ionized in the lattice, raising the Fermi level about 0.7 eV deep into the conduction band. X-ray photoelectron spectroscopy (XPS) is used to study chemical bonding and oxidation states. XPS analysis of the Sn 3d core levels reveals that lithium insertion in FTO induces a shift of 350 meV in the Sn 3d states, suggesting that lithium is incorporated into the SnO2 lattice.
The low dimensional chalcogenide materials with high band gap of ~1.8 eV, specially molybdenum di-sulfide (MoS2), have been brought much attention in the material science community for their usage as semiconducting materials to fabricate low scaled electronic devices with high throughput and reliability, this includes also photovoltaic applications. In this chapter, experimental data for MoS2 material towards developing the next generation of high-efficiency solar cells is presented, which includes fabrication of ~100 nm homogeneous thin film over silicon di-oxide (SiO2) by using radio frequency sputtering at 275 W at high vacuum~10−9 from commercial MoS2 99.9% purity target. The films were studied by means of scanning and transmission electron microscopy with energy disperse spectroscopy, grazing incident low angle x-ray scattering, Raman spectroscopy, atomic force microscopy, atom probe tomography, electrical transport using four-point probe resistivity measurement as well mechanical properties utilizing nano-indentation with continuous stiffness mode (CSM) approach. The experimental results indicate a vertical growth direction at (101)-MoS2 crystallites with stacking values of 7-laminates along the (002)-basal plane; principal Raman vibrations at E12g at 378 cm−1 and A1g at 407 cm−1. The hardness and elastic modulus values of H = 10.5 ± 0.1 GPa and E = 136 ± 2 GPa were estimated by CSM method from 0 to 90 nm of indenter penetration; as well transport measurements from −3.5 V to +3.5 V indicating linear Ohmic behavior.
This study employs DFT+U calculations to investigate the ferromagnetic properties of ErAl2 and ErNi2 Laves phases under an external hydrostatic pressure P (0 GPa ≤ P ≤ 1.0 GPa). The calculated magnetic moments per formula unit for both crystalline structures align with experimentally reported values: 4.40 μB/f.u. in the hard magnetization axis for ErAl2 and 5.56 μB/f.u. in the easy magnetization axis for ErNi2. The DFT results indicate that the magnetic moment remains unchanged up to 1 GPa of hydrostatic pressure, with no structural instabilities observed, as evidenced by a nearly constant formation energy for ErAl2 and ErNi2 alloys. The simulations confirm that the magnetic behavior of ErAl2 is primarily driven by the electrons localized in the f orbitals. In contrast, for ErNi2, both d and f orbitals significantly contribute to the total magnetic moment. Finally, the electronic specific heat coefficient was calculated and reported as a function of hydrostatic pressure up to P = 1.0 GPa for each Laves phase.