Ternary Zintl phosphides are promising light-absorbing semiconductors for thin-film optoelectronic applications, but strategies for controlling their microstructure and optoelectronic quality remain underexplored. Here, we report the synthesis of phase-pure SrZn2P2 thin films using radio-frequency co-sputtering in a PH3 + Ar atmosphere and investigate the impact of post-growth processing on their structural and optical properties. Grazing-incidence X-ray scattering and Raman spectroscopy confirm the formation of crystalline SrZn2P2 films over a finite compositional window. Optical measurements reveal strong absorption near the direct-band-gap energy ( 1.8 eV) and near-band-edge photoluminescence. Further, we have studied the effects of chemically compatible halide-assisted annealing. It is found that SrI2 treatments lead to pronounced grain growth and reduced diffraction peak broadening while preserving phase purity, in contrast to rapid thermal or forming-gas annealing. Notably, annealing with SrI2 at 450 °C significantly enhances both the intensity and spatial uniformity of the photoluminescence, thus connecting the observed microstructural consolidation with improved radiative recombination. Our study demonstrates that halide-assisted annealing provides an effective pathway for microstructural control in SrZn2P2 thin films and highlights a generalizable processing strategy for advancing Zintl phosphide semiconductors toward optoelectronic applications.

Ternary nitride alloys based on wurtzite AlN are a promising platform to realize functional materials, particularly ferroelectrics and optical emitters, that can smoothly integrate with conventional microelectronics. Here, a strategic design is presented to enable multifunctional materials by substituting multiple elements into AlN to create quaternary nitride alloys. By combining computational predictions and combinatorial thin film synthesis, the phase diagram of these quaternary Al-Sc-Gd-N alloys (or pseudo-ternary heterostructural AlN-ScN-GdN alloys) is successfully predicted as a function of effective temperature, and we experimentally grow Al 1 - x - y Sc x Gd y N ${\rm Al}_{1-x-y}{\rm Sc}_x{\rm Gd}_y{\rm N}$ thin films for the first time. It is revealed that Al 1 - x - y Sc x Gd y N ${\rm Al}_{1-x-y}{\rm Sc}_x{\rm Gd}_y{\rm N}$ crystallizes in a wurtzite-derived structure for x + y ≲ 0.35 $x+y \lesssim 0.35$ , consistent with the calculated phase diagram. The computational investigation explores whether co-substitution induces cooperative effects on these alloys' piezoelectric and ferroelectric properties, finding that it is beneficial for reducing the polarization switching barrier. We calculate that Al 1 - x - y Sc x Gd y N ${\rm Al}_{1-x-y}{\rm Sc}_x{\rm Gd}_y{\rm N}$ thin films should display ferroelectric switching. This is supported by our experimental measurements of a high optical bandgap, enhanced piezoelectric coefficient, and a change in the calculated polarization switching mechanism, and we achieve preliminary ferroelectric switching that experimentally realizes the prediction. Overall, our work sets the foundation toward quaternary wurtzite-nitride-based multifunctional materials, including piezoelectrics, ferroelectrics, and possibly even multiferroics.

Transition-metal nitrides in η-carbide type structures exhibit unusual bonding motifs and proximity to magnetic instabilities. Yet they remain unexplored in thin-film form due to the difficulty of stabilizing nitrogen-poor ternaries among competing phases. Here, we report the thin-film synthesis and phase-stability mapping of the η-nitride systems Fe-W-N and Fe-Mo-N. Amorphous Fe-M-N (M = W, Mo) combinatorial libraries deposited by reactive co-sputtering crystallize upon rapid thermal annealing, enabling systematic identification of synthesis windows as a function of composition and annealing temperature. Using laboratory powder X-ray diffraction and synchrotron grazing incidence wide angle X-ray scattering, we establish that Fe3Mo3N-based η-carbide phases form over a substantially broader compositional and thermal range than W-based compositions, where η structures are stabilized only when the films are Fe-rich. These trends are rationalized using mixed chemical-potential vs. composition phase diagrams that capture the narrow nitrogen chemical-potential stability of η-nitrides. Magnetic measurements reveal that ferromagnetism is induced in Fe-rich Fe3.54Mo2.46N with a small exchange-bias-like response that is absent in Fe3W3N-based compositions, highlighting the sensitivity of magnetic behavior to modest deviations from stoichiometry. This work establishes practical thin-film synthesis routes for η-nitride materials and demonstrates how composition can be tuned to access emergent magnetic phenomena in these complex nitrides.

Antiperovskite nitrides with the general formula M(3)AN have attracted significant attention due to their tunable electronic and magnetic properties. Among them are many cobalt-based compounds predicted to exhibit high thermodynamic stability and intriguing magnetic behavior. Here, we report the synthesis and magnetic characterization of epitaxial Co3ZnN thin films grown by radio frequency sputtering on SrTiO3 (STO) and MgO substrates. X-ray diffraction confirms phase-pure (00l)-oriented films with cube-on-cube epitaxy on STO, with a c-lattice parameter of 3.752 & Aring;. Magnetic measurements reveal clear hysteresis at 2 K with a coercive field of similar to 0.11 T and a small net moment of 0.108 mu(B)/f.u., suggesting either a canted antiferromagnetic (AFM) or ferrimagnetic (FiM) configuration. Temperature-dependent magnetization measurements show a transition near 25 K, with strong AFM interactions with Curie-Weiss temperature (Theta) = -80.13 K. Complementary density functional theory and Monte Carlo simulations indicate a ferromagnetic (FM) ground state, with the FM-AFM energy difference decreasing systematically with increasing supercell size, consistent with competition between FM and AFM/FiM interactions. These results highlight Co3ZnN as a magnetically complex antiperovskite nitride with competing exchange interactions.

Halide perovskites have revolutionized optoelectronics by demonstrating that long carrier lifetime can be achieved in materials processed in relatively uncontrolled environments, whereas conventional inorganic semiconductors typically suffer from short carrier lifetime unless very carefully prepared and postprocessed. Here, we report the discovery of exceptionally long photoexcited carrier lifetime in monoclinic ZnP2, effectively bridging the carrier lifetime gap between direct-gap inorganic semiconductors and halide perovskites. Through computational screening, ZnP2 is identified as a long carrier lifetime semiconductor characterized by an unconventional polyphosphide bonding, combining covalently bonded phosphorus chains and polar-covalent Zn-P tetrahedra. Experimentally, ZnP2 crystals synthesized from low-purity precursors exhibit bright band-to-band photoluminescence at 1.49 eV and carrier lifetimes of nearly 1 μs. Further analysis reveals that the polyphosphide bonding of ZnP2 suppresses the formation of deep intrinsic defects, making it defect resistant. Combined with its remarkable environmental stability, ZnP2 presents a highly promising material for solar absorbers and light emitters. Our work illustrates that underexplored inorganic materials spaces with unusual chemical bonding hold great promise for discovering novel optoelectronic materials.

Calciothermic reduction-diffusion (RD) is one of the leading synthesis methods for Sm2Fe17N3 (SmFeN), but sintering of such RD-derived powders is hampered by oxidation and CaO byproducts. Here, we systematically evaluate how post-synthesis washing solvents govern powder chemistry and magnetic performance. RD-synthesized SmFeN powder was washed with several aqueous and non-aqueous solvents using identical washing protocols. This was followed by an assessment of both the as-washed powder as well as after annealing at 425 degrees C. Phase content was quantified by synchrotron PXRD and Rietveld refinement and SEM/EDS. The oxygen content of the powders was determined via inert gas fusion and the magnetization by DC magnetometry. While all aqueous-based solutions were able to remove CaO, the non-aqueous solutions were only effective with extended washing times. Prior to annealing, the crystalline phases and magnetic properties of the as-washed powders were largely the same regardless of washing solvent. However, differences emerge after annealing, where water-based washing markedly lowers the coercivity (H-c similar to 3.8-4.3 kOe). In contrast, non-aqueous NH4Cl-methanol washing protocols were more effective in preserving coercivity (H-c similar to 4.9-5.9 kOe). We attribute this to lower oxygen content in the non-aqueous samples (similar to 9400 ppm v similar to 6400 ppm, respectively) which in turn reduced the formation of alpha-Fe during annealing. These results highlight the importance of solvent choice in washing RD-synthesized SmFeN and demonstrate that non-aqueous protocols, which better limit oxidation, outperform aqueous solvents despite the need for longer washing times.

The AM2Pn2 (A= Ca, Sr, Ba, Yb, Mg; M = Zn, Cd, Mg; and Pn = N, P, As, Sb, Bi) family of Zintl phases has been known as thermoelectric materials and has recently gained much attention for highly promising materials for solar absorbers in single-junction and tandem solar cells. In this paper, we will, from first principles, explore the entire family of AM2Pn2 compounds in terms of their ground-state structure, thermodynamic stability, and electronic structure. We also perform photoluminescence spectroscopy on bulk powder and thin film samples to verify our results, including the first measurements of the band gaps of SrCd2P2 and CaCd2P2. The AM2Pn2 compounds exhibit broad stability, are mostly isostructural to CaAl2Si2 (P3̅m1), and cover a wide range of band gaps from 0 to beyond 3 eV. This could make them useful for a variety of purposes, for which we propose several candidates, such as CaZn2N2 for tandem top cell solar absorbers and SrCd2Sb2 and CaZn2Sb2 for infrared detectors. By examining the band structures of the AM2Pn2, we find that Mg3Sb2 has the most promise as a thermoelectric material due to several off-Γ valence band pockets, which are unique to it among the compositions studied here.

By changing nitrogen chemical potential during synthesis of Mn–Ge–N ternary nitrides, both wurtzite MnGeN2 and antiperovskite Mn3GeN ternary phases are prepared. Antiperovskite films are optically opaque and conductive, while wurtzite films with Mn/(Mn + Ge) ≤ 0.5 transmit light above 2 eV. Alloys of Mn3GeN with Si and Al are also investigated. Mn3(Ge1−xAlx)N alloys with 0.07 ≤ x ≤ 0.16 exhibit a cubic (rather than tetragonal) structure. Mn3(Ge1−xSix)N with x ≤ 0.05 maintains the tetragonal structure but becomes cubic when x > 0.05. This study shows that care must be taken in the synthesis of Mn–Ge–N and similar nitrides, especially when materials are integrated into devices not amenable to structural and chemical probing.

Some ternary TM nitrides are predicted to adopt layered structures that make them interesting for thermoelectric conversion and quantum materials applications. Synthesis of TM ternary nitride films by physical vapor deposition often favors disordered 3D structures rather than the predicted 2D-like layered structure. In this study, we investigate the structural interplay in the Sc-Ta-N material system, focusing on ScTaN2. We use a two-step combinatorial approach to deposit Sc-Ta-N films by RF co-sputtering and then process the resulting 3D-structured precursor with RTA. Synchrotron GIWAXS on films annealed at 1200 °C for 20 min reveals the nucleation of the layered structure (P63/mmc) within a composition window of x = Sc/(Sc+Ta) = 0.2-0.5. We estimate the long-range order parameter in stoichiometric ScTaN2 films to be 0.86, corresponding to a fraction of antisites of 7

The crystal and magnetic structures of the nitride antiperovskite Mn_3GeN reveals ferrimagnetic order stemming from a distorted kagome-derived lattice of the Mn atoms. Polycrystalline Mn_3GeN was synthesized via a solid-state reaction and characterized using neutron powder diffraction, DC magnetometry, and first-principles calculations. Rietveld refinement reveals near-stoichiometric composition (Mn_3GeN_0.94(1)) adopting a tetragonal I4/mcm structure at T = 500 K and below, featuring axially distorted and tilted [NMn_6] octahedra that result in a buckled Mn kagome lattice. On heating, the tetragonal distortion and octahedral tilt angle decrease continuously before transitioning to the cubic Pm3̅m antiperovskite phase at T ≈ 524 K. Neutron diffraction and magnetometry together reveal noncollinear ferrimagnetic ordering. For 30 K ≤ T ≤ 500 K, the magnetic structure is described by a single propagation vector, k = (0, 0, 0), with inequivalent Mn1 and Mn2 sublattices that couple antiferromagnetically to yield a net moment. Density functional theory-based calculations show the different local moments originate from the bandwidths associated with the distinct Mn-N bond lengths. The temperature dependence of the sublattice moments indicates a compensation-like crossover between Mn1- and Mn2-derived magnetization near 380 K. These findings uncover a previously unrecognized subtlety in the magnetic and structural behavior of Mn_3GeN, highlighting the interplay between structural distortions, magnetic ordering, and electronic structure in kagome-derived antiperovskite materials.

Experimental synthesis and characterization of theoretically predicted compounds are important steps in the materials discovery pipeline. Here, we report on the synthesis of Co3PdN, which was recently predicted to be a stable magnetic antiperovskite. The Co3PdN thin films were grown by reactive sputtering and were confirmed to form in an antiperovskite crystal structure. The thermal stability of the compound is demonstrated up to 600 K by in situ X-ray diffraction, though the phase persists at slightly higher temperatures (700 K) in an air-free magnetometer. Both ab initio calculations and magnetization measurements find Co3PdN to be ferromagnetic with an experimentally determined Curie temperature of T C = 560 +/- 5 K. The saturation magnetization of 1.2 mu B/Co found in the experiment is slightly lower than the 1.7 mu B/Co value expected by theory. A narrow magnetic hysteresis loop with a coercive field of 100 Oe at low temperature suggests that Co3PdN might be useful in electronic applications requiring fast switching of the magnetization vector. While prior prediction of Co3PdN showed a gapped electronic band structure for each spin channel, we show that this was due to incomplete sampling of Brillouin zone paths and that band crossings exist along R-X|M and X|M-R paths. The metallic nature of Co3PdN is further confirmed by temperature-dependent transport measurements, which also show a considerable anomalous Hall effect. Altogether, this work represents an appreciable step toward understanding the synthesis, structure, stability, and properties of a new magnetic material.

Tetragonal ZnGa 2 Te 4 thin films with direct bandgap ∼1.86 eV show −2 mA cm −2 photocurrent, highlighting their potential as efficient photocathodes for photoelectrochemical CO 2 reduction.

We demonstrate the growth of size-controlled, high optical quality Zintl-phase BaCd2P2 colloidal quantum dots (QDs), an emerging semiconductor absorbing/emitting in the red and predicted to have favorable defect chemistry. The QDs are grown via hot injection of a phosphorus precursor into a solution of solubilized Ba and Cd precursors. The absorbance and photoluminescence (PL) are tunable via growth temperature and show a bandgap ranging from 1.47 to 1.81 eV, depending on the size, which ranges from 3 to 9 nm based on electron microscopy. Selected area electron diffraction is used to determine that the BaCd2P2 QDs crystallize in the P3̅m1 space group, same as the bulk material. Raman spectroscopy, powder X-ray diffraction, and X-ray fluorescence studies further confirm that BaCd2P2 QDs match those of the crystalline phase bulk material. The high optoelectronic quality is assessed by quantification of long-lived photoexcited carriers (∼160 ns average weighting), as determined by time-resolved PL spectroscopy, and bright red visible emission (∼21% PL quantum yield) despite no complex surface passivation. Furthermore, a demonstration of thin-film fabrication is shown via a solid state ligand exchange protocol. This synthetic protocol enables researchers to explore and utilize BaCd2P2 Zintl-phase QDs, as well as adjacent compositions, for a variety of optoelectronic applications enabled by their semiconducting properties.

Tantalum (Ta) has emerged as a promising low-loss material, enabling record coherence times in superconducting qubits. This enhanced performance is largely attributed to its stable native oxide, which may host fewer two-level system (TLS) defects, which are the key contributors to decoherence in superconducting circuits. Nevertheless, aluminum oxide remains the predominant choice for Josephson junction (JJ) barriers in most qubit architectures. Here, we investigate techniques for forming high-quality oxide layers on α-phase tantalum films to develop tantalum-oxide JJ barriers. We explore thermal oxidation in a tube furnace, rapid thermal annealing, and plasma oxidation of both room-temperature and heated Ta films, characterize the resulting structures using X-ray techniques and electron microscopy, and propose a mechanistic picture of the oxidation pathways. We find that plasma oxidation provides the smoothest Ta_2O_5 layers, is compatible with in situ Ta deposition, and offers thickness control through the annealing temperature, advantageous for JJ fabrication. Lastly, we evaluate methods for growing Ta/TaO_x/Ta trilayers. All trilayers showed c-axis-oriented columnar growth of the bottom Ta layer, with sapphire substrates producing larger, better-aligned grains yet higher dislocation densities than silicon. Nucleation of c-axis-oriented α-Ta on tantalum-oxide required an Nb seed layer, as direct Ta deposition yielded amorphous Ta. These results demonstrate the feasibility of α-Ta/Nb/TaO_x/α-Ta stacks for JJs with clean interfaces.

Ternary transition metal (TM) nitrides have gained significant attention in thin film research due to their promising properties for a broad range of applications. Particularly, some of the ternary TM nitrides have been predicted to adopt layered structures that make them interesting for thermoelectric conversion and quantum materials applications. Unfortunately, synthesis of TM ternary nitride films by physical vapor deposition often favors disordered 3D structures rather than the predicted 2D-like layered structure. In this study, we investigate the structural interplay in the Sc-Ta-N ternary system using a combinatorial approach. Combinatorial libraries ScxTa1-xN are synthesized following a two-step method: First, deposit film precursors by cosputtering and then process the resulting 3D-structured samples with rapid thermal annealing. Synchrotron grazing-incidence wide-angle x-ray scattering on films annealed at 1200(degrees)C for 20 min leads to the nucleation of ScTaN2 layered structure (P6(3)/mmc) near stoichiometry. We find that the layered structure can accommodate large off-stoichiometry in the Ta-rich region (x<0.5), facilitated by the alloying with quasi-isostructural Ta5N6 compound that exists on a composition tie line at x=0. While focusing on ScTaN2, we estimate the long-range order parameter in near-stoichiometric films to be 0.86, corresponding to a fraction of Sc/Ta antisites of 7%. Transport measurements on ScTaN2 reveal a nearly temperature-independent high carrier density (10(21)cm(-3)), suggesting a heavily doped semiconductor or semimetallic character, consistent with a small positive Seebeck coefficient of +19 mu V/K. The carrier mobility at 2 K is relatively small (9.5cm(2)V(-1)s(-1)) and the residual-resistivity ratio is minor, suggesting that electrical conduction is dominated by defects or disorder. Measured magnetoresistance suggests possible weak antilocalization at 2 K. This paper highlights the interplay between ScTaN2 and Ta5N6 crystal structures in stabilizing layered materials, emphasizes the importance of cation order/disorder for potential tunable alloys, and suggests that ScTaN2 is a promising platform for exploring electronic properties.

The development of tandem photovoltaics and photoelectrochemical solar cells requires new absorber materials with bandgaps in the range of approximate to 1.5-2.3 eV, for use in the top cell paired with a narrower-gap bottom cell. An outstanding challenge is finding materials with suitable optoelectronic and defect properties, good operational stability, and synthesis conditions that preserve underlying device layers. This study demonstrates the Zintl phosphide compound CaZn2P2 as a compelling candidate semiconductor for these applications. Phase-pure, approximate to 500 nm-thick CaZn2P2 thin films are prepared using a scalable reactive sputter deposition process at growth temperatures as low as 100 degrees C, which is desirable for device integration. Ultraviolet-visible spectroscopy shows that CaZn2P2 films exhibit an optical absorptivity of approximate to 10(4) cm(-1) at approximate to 1.95 eV direct bandgap. Room-temperature photoluminescence (PL) measurements show near-band-edge optical emission, and time-resolved microwave conductivity (TRMC) measurements indicate a photoexcited carrier lifetime of approximate to 30 ns. CaZn2P2 is highly stable in both ambient conditions and moisture, as evidenced by PL and TRMC measurements. Experimental data are supported by first-principles calculations, which indicate the absence of low-formation-energy, deep intrinsic defects. Overall, this study shall motivate future work integrating this potential top cell absorber material into tandem solar cells.

Controlled synthesis of metastable materials away from equilibrium is of interest in materials chemistry. Thin-film deposition methods with rapid condensation of vapour precursors can readily synthesize metastable phases but often struggle to yield the thermodynamic ground state. Growing thermodynamically stable structures using kinetically limited synthesis methods is important for practical applications in electronics and energy conversion. Here we reveal a synthesis pathway to thermodynamically stable, ordered layered ternary nitride materials, and discuss why disordered metastable intermediate phases tend to form. We show that starting from elemental vapour precursors leads to a 3D long-range-disordered MgMoN2 thin-film metastable intermediate structure, with a layered short-range order that has a low-energy transformation barrier to the layered 2D-like stable structure. This synthesis approach is extended to ScTaN2, MgWN2 and MgTa2N3, and may lead to the synthesis of other layered nitride thin films with unique semiconducting and quantum properties. Synthesis of metastable materials away from thermodynamic equilibrium has been a challenge in materials chemistry, but thin-film methods often struggle to yield ground-state structures. Now, a synthesis pathway to thin films of stable layered ternary nitrides is revealed, and the tendency for metastable intermediate formation is discussed.

Recent high-throughput computational searches have predicted many novel ternary nitride compounds providing new opportunities for materials discovery in underexplored phase spaces. Nevertheless, there are hardly any predictions and/or syntheses that incorporate only transition metals into new ternary nitrides. Here, we report on the synthesis, structure, and properties of MnCoN2, a new ternary nitride material comprising only transition metals and N. We find that crystalline MnCoN2 can be stabilized over its competing binaries, and over a tendency of this system to become amorphous, by controlling growth temperature within a narrow window slightly above ambient condition. We find that single-phase MnCoN2 thin films form in a cation-disordered rocksalt crystal structure. X-ray photoelectron spectroscopy analysis suggests that MnCoN2 is sensitive to oxygen through various oxides and hydroxides binding to cobalt on the surface. X-ray absorption spectroscopy is used to verify that Mn3+ and Co3+ cations exist in an octahedrally coordinated environment, which is distinct from a combination of CoN and MnN binaries and in agreement with the rocksalt-based crystal structure prediction. Magnetic measurements suggest that MnCoN2 has a canted antiferromagnetic ground state below 10 K. We extract a Weiss temperature of theta = - 49 . 7 K, highlighting the antiferromagnetic correlations in MnCoN2.