Scandium nitride (ScN) is a cubic NaCl-structured, degenerate, narrow-bandgap, n-type semiconductor that exhibits remarkable semiconducting, thermoelectric and plasmonic properties. However, its properties are sensitive to several types of defects, such as crystal defects, morphology, intentional or unintentional doping. For the purpose of reducing the deposition temperature of ScN, a series of films were deposited in the temperature range of 250–850 °C using a high-power impulse magnetron sputtering technique. While the stoichiometry and crystal structure remained unaffected in the sample series, the optical and electrical properties were affected when the temperature was decreased. Using in-depth XRD, optical and electrical characterizations, the effect of strain and dislocations on the semiconductor properties of ScN was evaluated. A reduction in the deposition temperature from 850 °C to 450 °C yielded a slow change in the electrical and optical properties, while a drastic change occurred for the films deposited below 450 °C. The main cause of the deterioration of the electrical transport properties (σ/10 000; n/100, and µ/100) was attributed to a high dislocation density (1011 cm−2) along with a rhombohedral distortion of the ScN cell (α: 90° → 88.6°), which was the main cause of the variation in the electrical transport. The presence of dislocations/crystal defects in the film generated defect states near the edges of the valence and conduction bands, softening the edges and impacting the electron density and mobility. The best thermoelectric properties of ScN were obtained when it was grown at 850 °C and were further modified and altered by strain engineering.

Tantalum nitride (Ta3N5) is a promising semiconductor for solar-driven photoelectrochemical (PEC) water splitting, but its performance is limited by intrinsic defects. Here, we investigate the effect of titanium (Ti) doping (0–10 at%) on the structural, compositional, and optoelectronic properties of Ta3N5 thin films. At low concentrations (<2 at%), Ti4+ preferentially substitutes Ta at four-coordinated sites, enhancing nitrogen incorporation and suppressing defect states associated with under-coordinated Ta. This leads to improved carrier dynamics and prolonged electron–hole lifetimes. Higher doping levels (≥3.5 at%) result in occupation of three-coordinated sites, inducing increase in the oxygen content, lattice distortion, and defect formation that deteriorate carrier lifetimes. PEC measurements reveal that optimized Ti doping significantly reduces charge transfer resistance and nearly seven-fold increase in the photocurrent. These findings underscore the importance of controlled Ti doping for defect engineering and band structure tuning to boost the PEC performance of Ta3N5 thin films.

The transport properties of CrN thin films deposited on sapphire have been tailored through structural modifications induced by cumulative argon implantation. As-grown samples experience the typical structural transition in CrN films from orthorhombic at low temperature to cubic above the N & eacute;el temperature (approximate to 280 K) and exhibit a metallic-like conduction in both phases. With increasing implantation dose, the conduction mode shifts to a semiconductor-like behavior in both phases, albeit at different damage levels. Analysis of the results suggests that hopping conduction becomes dominant beyond a given damage threshold. The results highlight a promising correlation between defect engineering and conduction mechanisms, offering valuable insights into the versatile electrical properties of CrN films. These implantation-induced defects scatter carriers, leading to a decrease in their mobility. As the implantation dose increases, the defect landscape evolves, modifying the density of states. However, up to a dose of 0.050 dpa, no significant influence on phonon scattering is observed. This approach demonstrates that ion implantation enables precise tuning of CrN's electrical properties without affecting thermal conductivity, offering valuable insights into defect engineering in transition metal nitrides and underscoring its potential for transport properties decorrelation.

We report on the formation of the Cr2C compound using chemical etching-free methodology to extract Al from a Cr2AlC MAX phase thin film. Cr2AlC/Cu assemblies were deposited on sapphire substrates, using magnetron sputtering, and were subsequently annealed in vacuum. The Al from the MAX phase was shown to diffuse into Cu resulting in the formation of Al4Cu9 and causing the MAX phase to collapse into Cr2C grains. These carbide grains were characterized by transmission electron microscopy and the interatomic distances extracted were in good agreement with ab initio calculations predicting the equilibrium volume of the Cr2C phase.

Transition metal nitrides are a fascinating class of hard coating material that provides an excellent platform for investigating superconductivity and fundamental electron-phonon (e-ph) interactions. In this work, the structural, morphological, and superconducting properties have been studied for Mo2N thin films deposited via direct current magnetron sputtering on c-plane Al2O3 and MgO substrates to elucidate the effect of internal strain on superconducting properties. High-resolution X-ray diffraction and time-of-flight elastic recoil detection analysis confirm the growth of single-phase Mo2N thin films exhibiting epitaxial growth with twin-domain structure. Low-temperature electrical transport measurements reveal superconducting transitions at approximate to 5.2 and approximate to 5.6 K with corresponding upper critical fields of approximate to 5 and approximate to 7 T for the films deposited on Al2O3 and MgO, respectively. These results indicate strong type-II superconductivity, and the observed differences in superconducting properties are attributed to substrate-induced strain, which leads to higher e-ph coupling for the film on MgO substrate. These findings highlight the tunability of superconducting properties in Mo2N films through strategic substrate selection.

The influence of heavy atom incorporation (in this case, tungsten, W) into scandium nitride is examined to assess its impact on the electronic structure and associated thermoelectric properties. Incorporating W, with its 5d valence electrons, is expected to shift the Fermi level into the conduction band. A solid solution of Sc1−x​Wx​Ny​ system is also expected to form as ScN exhibits the largest unit cell among the early 3d transition metal nitrides. However, phase separation is initiated at x = 0.10 and results in Sc- and W-rich regions occurring through conventional nucleation and growth. High-temperature nitrogen substoichiometry (at ∼800 °C) and formation of secondary phase is governed by inducing N vacancies in the crystal system. The N/W ratio alters the occupancy of the nonbonding t2g states in the valence band and results in phase instability. The Sc1−x​Wx​Ny​ system is found to be less covalent than a ScN reference sample indicating the presence of ionic and metallic bonds as observed through spectroscopic studies. A unique combination of a metal-like Seebeck coefficient with increased electrical resistivity is found for the Sc1−x​Wx​Ny​ system compared to the ScN reference. This study aims to elucidate the structural, microstructural, and electronic properties of the Sc1-xWxNy system and establishing a correlation with thermoelectric properties, through a combined experimental and theoretical approach.

This study investigates the effects of incorporating 11B4C interlayers into Fe/Si multilayers, with a focus on interface quality, reflectivity, polarization, and magnetic properties for polarizing neutron optics. It is found that the introduction of 1-2 & Aring; 11B4C interlayers significantly improves the interface sharpness, reducing interface width and preventing excessive Si diffusion into the Fe layers. X-ray reflectivity and polarized neutron reflectivity measurements show enhanced reflectivity and polarization, with a notable increase in polarization for 30 & Aring; period multilayers. The inclusion of interlayers also helps prevent the formation of iron-silicides, improving both the magnetic properties and neutron optical performance. However, the impact of interlayers is less pronounced in thicker-period multilayers (100 & Aring;), primarily due to the ratio between layer and interface widths. These results suggest that 11B4C interlayers offer a promising route for optimizing Fe/Si multilayer performance in polarizing neutron mirrors.

Pyrite is the most common among the group of sulfide minerals in the Earth and abundant in most geological settings. This gangue mineral in association with garnet, hematite, magnetite, and other sulfide minerals acts as an indicator mineral in the Kubi concession of the Asante Gold corporation in Ghana. X-ray diffraction (XRD), air annealing in a furnace, energy-dispersive x-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were applied to investigate the crystal structure, identify individual elements, permanence, transformation, and chemical/electronic properties of such pyrite. The study aims to identify individual elements and to gain an understanding of the surface reaction mechanisms, as well as the properties of precipitated pyrite particles observed during the hydrothermal formation of the ore deposit. XRD shows that pristine and annealed samples contain some hematite and quartz besides pyrite. Results from air annealing indicate that the relationship between pyrite and hematite-magnetite is controlled by temperature. EDX reveals that the sample has O and C as contaminants, while XPS in addition reveals Ba, Au, P, Al, and N. These elements are attributed to pyrite that bonds metallically or covalently to neighboring ligands/impurity minerals such as oxides, chalcogenide sulfides, as well as the gangue alteration minerals of magnetite and hematite in the pyrite sample.

These findings suggest that during the hydrothermal flow regime, pyrite, pathfinder elements, and impurity minerals/metals were in contact with quartz minerals before undergoing hematite transformation, which thus becomes an indicator mineral in the Kubi gold concession.

Fiber-textured and epitaxial NiO thin films were deposited on Si(100), c-Al₂O₃, and muscovite mica(001) sub-strates using reactive magnetron sputtering at substrate temperatures of 300 °C and 400 °C, to investigate theeffect of film thickness and substrate temperature on epitaxial growth of NiO films. The as-deposited filmsexhibited a face-centered cubic structure with a larger lattice constant, attributed to strain induced during thesputtering process. With an increase in substrate temperature to 400 °C, the d-spacing decreased due to strainrelease, approaching the NiO bulk value for the thickest film. The NiO film grown on Si(100) displayed fibertexture. On c-plane sapphire, NiO thin films exhibited twin domains and three-fold symmetry, consistent withexpected crystallographic orientation relationship for NaCl-structured materials onsapphire: (111)_NiO ‖ (0001)_Al2O3 and [011]_NiO ‖ [1010]_Al2O3, [011]_NiO ‖[1010]_Al2O3. On muscovite mica(001)substrates, the observed epitaxial shows that the mechanism is conventional epitaxy, rather than van der Waalsepitaxy, consistent with the epitaxial growth of the non-layered non-van-der-Waals compound NiO. The epitaxialrelationship was identified as of (111)_NiO‖(001)_Mica and [011]_NiO ‖[010]_Mica, [011]_NiO ‖[010]_Mica.

CrN-based thin films are emerging as thermoelectric materials for energy harvesting. Their thermoelectric properties depend on phase composition and stoichiometry, necessitating control over the nitrogen content and how it affects the phase composition. Here, the effect of high-temperature ammonia annealing on the thermoelectric properties as well as crystal structure of thin films of Cr-N on c-plane sapphire (Al2O3(0001)) was investigated. Single-phase (cubic CrN) and mix-phase (cubic CrN + hexagonal-Cr2N) Cr-N films were annealed in ammonia, converting any secondary phase of hexagonal Cr2N to cubic CrN. The thermoelectric properties of the films that contained a secondary phase of hexagonal (CrN)-N-2 greatly improved upon annealing, with an increase of 900% to 0.5 x 10-3 W m(-1) K-2 for the film annealed at 800 degrees C for 2 h. Annealing of single-phase films of cubic CrN resulted in films with near-insulating electrical properties. For the thermoelectric applications of CrN, ammonia annealing can be beneficial over meticulous deposition control.