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A two-step synthesis approach was utilized to grow CaMnO3 on M-, R- and C-plane sapphire substrates. Radio-frequency reactive magnetron sputtering was used to grow rock-salt-structured (Ca, Mn)O followed by a 3-h annealing step at 800 °C in oxygen flow to form the distorted perovskite phase CaMnO3. The effect of temperature in the post-annealing step was investigated using x-ray diffraction. The phase transformation to CaMnO3 started at 450 °C and was completed at 550 °C. Films grown on R- and C-plane sapphire showed similar structure with a mixed orientation, whereas the film grown on M-plane sapphire was epitaxially grown with an out-of-plane orientation in the [202] direction. The thermoelectric characterization showed that the film grown on M-plane sapphire has about 3.5 times lower resistivity compared to the other films with a resistivity of 0.077 Ωcm at 500 °C. The difference in resistivity is a result from difference in crystal structure, single orientation for M-plane sapphire compared to mixed for R- and C-plane sapphire. The highest absolute Seebeck coefficient value is − 350 µV K−1 for all films and is decreasing with temperature.

Ion implantation is a widely used technique to introduce defects in low-dimensional materials and tune their properties. Here, we investigate the thermoelectric properties of scandium nitride thin films implanted with helium ions, revealing a positive impact of defect engineering on thermoelectric performance. Transport properties modeling and electron microscopy provide insights on the defect distribution in the films. The electrical resistivity and Seebeck coefficient increase significantly in absolute values after implantation and partially recover upon annealing as some of the implantation-induced defects heal. The thermal conductivity decreases by 46 % post- implantation due to the formation of extended defects and nanocavities. Consequently, the thermoelectric figure of merit zT doubles for the sample annealed at 673 K. These findings highlight the potential of controlled ion implantation to enhance thermoelectric properties in thin films, paving the way for further optimization through defect engineering. Ion implantation is a widely used technique to add defects into low dimensional materials to tune their properties. Here, the thermoelectric properties of scandium nitride films were improved by implanting helium ions

(Ti0.5, Mg0.5)N thin films were synthesized by reactive dc magnetron sputtering from elemental targets onto c-cut sapphire substrates. Characterization by θ–2θ X-ray diffraction and pole figure measurements shows a rock-salt cubic structure with (111)-oriented growth and a twin-domain structure. The films exhibit an electrical resistivity of 150 mΩ·cm, as measured by four-point-probe, and a Seebeck coefficient of −25 µV/K. It is shown that high temperature (~800 °C) annealing in a nitrogen atmosphere leads to the formation of a cubic LiTiO2-type superstructure as seen by high-resolution scanning transmission electron microscopy. The corresponding phase formation is possibly influenced by oxygen contamination present in the as-deposited films resulting in a cubic superstructure. Density functional theory calculations utilizing the generalized gradient approximation (GGA) functionals show that the LiTiO2-type TiMgN2 structure has a 0.07 eV direct bandgap.

Solid‐state precipitation can be used to tailor material properties, ranging from ferromagnets and catalysts to mechanical strengthening and energy storage. Thermoelectric properties can be modified by precipitation to enhance phonon scattering while retaining charge‐carrier transmission. Here, unconventional Janus‐type nanoprecipitates are uncovered in Mg3Sb1.5Bi0.5 formed by side‐by‐side Bi‐ and Ge‐rich appendages, in contrast to separate nanoprecipitate formation. These Janus nanoprecipitates result from local comelting of Bi and Ge during sintering, enabling an amorphous‐like lattice thermal conductivity. A precipitate size effect on phonon scattering is observed due to the balance between alloy‐disorder and nanoprecipitate scattering. The thermoelectric figure‐of‐merit ZT reaches 0.6 near room temperature and 1.6 at 773 K. The Janus nanoprecipitation can be introduced into other materials and may act as a general property‐tailoring mechanism. Bi‐/Ge‐rich Janus nanoprecipitates in Mg3Sb1.5Bi0.5 compounds are uncovered by electron microscopy and atom probe tomography. This complex Janus nanoprecipitate results from local comelting of Bi and Ge during sintering and enables an amorphous‐like lattice thermal conductivity near room temperature. The mechanistic understanding of thermal‐conductivity reduction is supported by modelling the material systems with and without precipitates.

Thin films of CrMoVN are deposited on c‐plane sapphire (Al2O3 (0001)) by direct current reactive magnetron sputtering, to investigate the effects of Mo and V addition to CrN‐based films. All films grow epitaxially, but Mo incorporation affects the crystal structure and nitrogen content. All films in the CrMoVN series are understoichiometric in nitrogen, but largely retain the NaCl B1 structure of stoichiometric CrN films. Addition of vanadium increases the phase‐stability range of the cubic phase, allowing for higher solubility of Mo than what has previously been reported for cubic CrN. The Seebeck coefficient and electrical resistivity are greatly affected by the alloying, showing a decrease of the Seebeck coefficient along with a decrease in resistivity. Cr0.83Mo0.11V0.06Nz shows a 70% increase in power factor (S2σ = 0.22 mW m−1 K−2) compared to the reference CrNz (S2σ = 0.13 mW m−1 K−2). Thermoelectric (TE) materials are in use in several applications, but often have too low efficiency. For more widespread use of these materials, fundamental research on TE material system is necessary. In this work, alloying in CrN, with the hope of pushing a material with great promise closer to applications, is investigated.

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 Néel temperature (≈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. This study demonstrates how implantation‐induced defects in CrN thin films enable controlled tuning of electrical transport from metallic to semiconductor‐like behavior while preserving thermal conductivity. Through cumulative argon implantation, defect landscapes are engineered to manipulate carrier mobility and conduction mechanisms, revealing key insights into decoupling electrical and thermal properties in transition metal nitrides.

Janus Nanoprecipitation In article number 2202594, Yuan Yu, Per Eklund, Weishu Liu, and co‐workers uncover Bi‐/Ge‐rich Janus nanoprecipitates in Mg3Sb1.5Bi0.5 compounds by electron microscopy and atom probe tomography. This Janus nanoprecipitate enables an amorphous‐like lattice thermal conductivity and provides a new perspective for tailoring nanostructures for improving thermoelectric properties.

Phase formation, morphology, and optical properties of Ti(O,N) thin films with varied oxygen-to- nitrogen ration content were investigated. The films were deposited by magnetron sputtering at 500 °C on Si(100) and c-plane sapphire substrate. A competition between a NaCl B1 structure TiN 1−x O x , a rhombohedral structure Ti 2 (O 1−y N y ) 3 , and an anatase structure Ti(O 1−z N z ) 2 phase was observed. While the N-rich films were composed of a NaCl B1 TiN 1−x O x phase, an increase of oxygen in the films yields the growth of rhombohedral Ti 2 (O 1-y N y ) 3 phase and the oxygen-rich films are comprised of a mixture of the rhombohedral Ti 2 (O 1−y N y ) 3 phase and anatase Ti(O 1−z N z ) 2 phase. The optical properties of the films were correlated to the phase composition and the observation of abrupt changes in terms of refractive index and absorption coefficient. The oxide film became relatively transparent in the visible range while the addition of nitrogen into films increases the absorption. The oxygen rich-samples have bandgap values below 3.75 eV, which is higher than the value for pure TiO 2 , and lower than the optical bandgap of pure TiN. The optical properties characterizations revealed the possibility of adjusting the band gap and the absorption coefficient depending on the N-content, because of the phases constituting the films combined with anionic substitution.

Cr2N is commonly found as a minority phase or inclusion in stainless steel, CrN-based hard coatings, etc. However, studies on phase-pure material for characterization of fundamental properties are limited. Here, Cr2N thin films were deposited by reactive magnetron sputtering onto (0001) sapphire substrates. X-ray diffraction and pole figure texture analysis show Cr2N (0001) epitaxial growth. Scanning electron microscopy imaging shows a smooth surface, while transmission electron microscopy and X-ray reflectivity show a uniform and dense film with a density of 6.6 g cm−3, which is comparable to theoretical bulk values. Annealing the films in air at 400 °C for 96 h shows little signs of oxidation. Nano-indentation shows an elastic–plastic behavior with H = 18.9 GPa and Er = 265 GPa. The moderate thermal conductivity is 12 W m−1 K−1, and the electrical resistivity is 70 μΩ cm. This combination of properties means that Cr2N may be of interest in applications such as protective coatings, diffusion barriers, capping layers and contact materials.

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 ≈5.2 and ≈5.6 K with corresponding upper critical fields of ≈5 and ≈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. Compressive strain in Mo2N thin films on MgO substrates significantly enhances electron‐phonon coupling, resulting in a ∼25% increase in the upper critical field compared to films on Al2O3 substrate. This finding demonstrates an effective strategy for achieving higher‐performance superconducting devices by utilizing strain as a tunable parameter to optimize superconducting properties.