Cu3N Films Research Articles

Evaluating Sulfur as a P‐Type Dopant in Cu3N Using Ab Initio Methods

Copper nitride (Cu3N) is an environmentally friendly semiconducting material with bipolar doping capability and is of interest to various applications. As deposited Cu3N films have inherent n‐type conductivity, further controllable n‐type doping is possible by introducing metal impurities. First‐principles methods based on density functional theory and beyond have been employed to study the p‐type doping behavior of sulfur atoms in Cu3N. The structural, electronic, optical, and thermal properties of pure Cu3N and sulfur‐doped Cu3N are computed for single and 3 × 3 × 3 supercells. Sulfur doping causes a shift from intrinsic n‐type to p‐type behavior. This study confirms that sulfur atoms in sulfur‐doped copper nitride preferentially occupy interstitial positions over nitrogen substitution, face‐centered, or copper substitution sites. Due to this change and an increased lattice constant, Cu3N becomes a softer material with a larger bandgap in the single‐cell alloy. Doped Cu3N supercell results show significant changes in optical properties appropriate for solar and other photoelectric applications. Cu3N:S exhibits remarkable enhancements in power factor and thermal and electrical conductivity, indicating potentially better performance in thermoelectric applications. The dielectric constant and absorption coefficient also significantly change with the incorporation of sulfur into Cu3N.

Effect of substrate temperature and position on properties of Cu3N thin films deposited by reactive radio frequency magnetron sputtering

Copper nitride (Cu3N) thin films were deposited on soda lime glass (SLG) substrates by reactive radio frequency (RF) magnetron sputtering using a pure Cu target in the presence of argon and nitrogen. The structural, optical, and electrical properties of the Cu3N films were investigated systematically on substrate temperature and position, demonstrating that both parameters strongly influence the properties of Cu3N thin films. XRD patterns revealed the formation of the Cu3N phase at all substrate temperatures and positions. The transmittance of the Cu3N thin films was over 80 % in the transparent region and the band gap for Cu3N was determined to 1.7–1.9 eV with a very high absorption coefficient above 104 cm−1. The n-type conductivity was observed in every Cu3N film but the resistivity varied considerably with both substrate temperature and position. The promising physical properties of Cu3N thin films suggest their potential application in optoelectronic devices such as thin film solar cells.

Phase Composition and Structure of Ultrathin Nanocrystalline Cu-Ni Film Alloys

The results of studying the morphology, crystal structure and phase composition of ultrathin Cu-Ni alloy films with thicknesses up to d = 10 nm and concentrations 0 < Cu < 100 at.% are presented.

Nickel Salt Dependency as Catalyst in the Plating Bath on the Film Properties of Cu/Cu-Ni

Metal plating frequently employs nickel (Ni) and copper (Cu) as anodes. Cu/ Cu-Ni film formed has many advantages, such as better corrosion resistance and high hardness characteristics. This study aims to assess the properties of Cu/Cu-Ni film, such as phase, surface morphology, crystallographic orientation, hardness, corrosion analysis, and contact angle, which were fabricated using electrodeposition with various Ni salt additions (0.3, 0.5 and 0.7 M). In addition, the cathode current efficiency (CCE) and deposition rate of the Cu/Cu-Ni electrodeposition were also investigated. An increase in Ni salt in the plating bath could enhance the pH, promoting higher CCE and depleting hydrogen evolution at the cathode, leading to the presenting Ni phase in the alloy. The higher concentration of Ni salt in the solution could also enhance the deposition rate due to a shift to a pH value, which affects the roughening of the surface morphology, promoting a higher contact angle. All crystal structures generated by Cu/Cu-Ni electrodeposition were FCC, with the preferred orientation of the (111) plane. Crystallite size and lattice strain depend on the deposition rate. Less crystallite size and lattice strain affect the film’s hardness and corrosion resistance. Moreover, the third bath had the resulting Cu-Ni layer with the best hardness and corrosion rate of around 136 HV and 0.081 mmpy.

The Piezoresistive Performance of CuMnNi Alloy Thin-Film Pressure Sensors Prepared by Magnetron Sputtering

Effects of varying Mn and Ni concentrations on the structure and piezoresistive properties of CuMnNi films deposited by magnetron sputtering with a segmented target were investigated. An increase in the Ni content refines the CuNi film grains, inducing an increase in defects such as internal micropores and a decrease in film density. At the same time, the positive piezoresistive coefficient of the film changes to negative. When 17.5 at.% Ni was added, the negative piezoresistive coefficient of the CuNi film was −2.0 × 10−4 GPa−1. The doping of Ni has a weakening effect on the positive piezoresistive effect of the film. Adding Mn into Cu refines the film grains while increasing the film density. The surface roughness of the film decreases with the increase in Mn content. When the Mn content was 16.7 at.%, the piezoresistive coefficient reached the largest recorded value of 23.81 × 10−4 GPa−1, and the film exhibited excellent repeatability in multiple piezoresistive tests. After the CuMn film with 16.7 at.% Mn was annealed at 400 °C for 2 h, the film grains grew slightly and the film residual stress decreased. The optimization of the film structure can reduce the scattering of electrons during transportation. The piezoresistive coefficient of the film was further improved to 35.78 × 10−4 GPa−1.

Impact of alloying on electrocatalytic hydrogenation of benzaldehyde over sputtered NiCu film catalysts

In this work, we prepare a series of NiCu alloy film catalysts with different contents by magnetron sputtering to investigate the synergistic effect between Ni and Cu in electrocatalytic hydrogenation of benzaldehyde. The results show that alloying of Ni and Cu can significantly enhance the electrocatalytic activity of benzaldehyde hydrogenation. With the increase of Ni content, the conversion rate of benzaldehyde increases two to three orders of magnitude, and the Faradaic efficiency of the Ni-rich catalysts is higher than that of the Cu-rich catalysts. In addition, the alloy composition affects the relative coverages of H and benzaldehyde, leading to different reaction orders in benzaldehyde. The boosted electrocatalytic activity with the increase of Ni content is in accordance with the electrochemical impedance spectroscopy that increasing Ni content can decrease the charge transfer resistance of the alloy catalysts.

Mechanical Properties of Thermally Annealed Cu/Ni and Cu/Al Multilayer Thin Films: Solid Solution vs. Intermetallic Strengthening

In this study, Cu/Ni and Cu/Al multilayers, with individual layer thickness varying from 25 nm to 200 nm, and co-sputtered Cu-Ni and Cu-Al single layer films were deposited at room temperature via magnetron sputtering and further annealed from 100 °C to 300 °C. The mechanical and microstructural properties of the as-deposited and annealed samples were characterized by nanoindentation, x-ray diffraction, and scanning electron microscopy. Both multilayer systems exhibit an increase in hardness with increasing annealing temperature. However, the Cu/Ni system shows a gradual and moderate hardness increase (up to 30%) from room temperature to 300 °C, while the Cu/Al system displays a sharp hardness surge (~150%) between 125 °C and 200 °C. The co-sputtered Cu-Ni and Cu-Al samples consistently demonstrate higher hardness than their multilayered counterparts, albeit with distinctly different temperature dependence—the hardness of Cu-Ni increases with annealing temperature while Cu-Al maintains a constant high hardness throughout the entire temperature range. The distinct thermal strengthening mechanisms observed in the two metallic multilayer systems can be ascribed to the formation of solid solutions in Cu/Ni and the precipitation of intermetallic phases in Cu/Al. This study highlights the unique advantage of intermetallic strengthening in metallic multilayer systems.

Fabrication of transparent p-CuI/n-ZnO heterojunction with excellent ideality factor

Copper iodide (CuI) is an intrinsically transparent p-type semiconductor with a wide band gap of about 3.1 eV. In this work, Cu3N films were prepared as precursors through high-power impulse magnetron sputtering and then were solid-phase iodinated at room temperature for the preparation of transparent CuI films. Subsequently, transparent p-CuI/n-ZnO heterojunctions were fabricated wherein ZnO layers were deposited by radio frequency magnetron sputtering. After the properties are optimized by annealing, the heterojunctions exhibit significant rectification characteristics. The influence of annealing temperature on the electrical properties of the heterojunctions have been investigated. The optimal ideality factor of about 1.22 can be obtained with a rectification ratio of 1.05 × 105 after the heterojunctions annealing at 100 °C. This value is superior to most of the results reported in the literature. Meanwhile, the light-to-dark current ratio and the transmittance in the visible region of the heterojunction have also been studied. The light-to-dark current ratio is significant at 6.42 × 106. The average transmittance of the heterojunctions is 72.7%. These findings demonstrate the potential applications of CuI for optoelectronic devices and the promising prospects of p-CuI/n-ZnO heterojunction-based photodetectors and other optoelectronic devices.

(Invited) Magnetic Field Assisted Electrodeposition of Topographically and Chemically Structured Copper-Nickel Deposits

Electrodeposition under the influence of magnetic field has sparked the interest of researchers for decades. The beneficial effects of homogenous magnetic fields on electrodeposition enable increased deposition rates as well as smoother deposits.[1] These effects have been intensively studied and attributed to magnetohydrodynamic forces. Conversely, several questions remain unanswered with respect to the beneficial influence of heterogeneous magnetic fields.[2] There, local convection allows structuring of deposit morphologies; however, it has not yet been reported if magnetic gradients can be used to induce local compositional changes.[3] Here, we investigate the opportunity to induce both, topographic and chemical structuring of electrodeposits by magnetic gradients.For this purpose, potentiostatic deposition of CuNi films is carried out on an Au coated glass slide using a sulphate-based aqueous electrolyte. An iron wire template is magnetised by a permanent magnet and placed below the working electrode to apply well defined, high magnetic gradients during electrodeposition. The obtained Cu-Ni deposits are analysed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The results of these measurements reveal that the deposited film topography follows the distribution of superimposed magnet field gradients and that a local compositional change of the deposits is possible. Thus, our results open up a new path to control the local morphology of complex deposits structures and other properties of films by magnetic gradient assisted electrodeposition. References (1) Uhlemann, M.; Tschulik, K.; Gebert, A.; Mutschke, G.; Fröhlich, J.; Bund, A.; Yang, X.;Eckert, K. Eur. Phys. J. Spec. Top. 2013, 220, 287–302.(2) Mutschke, G.; Tschulik, K.; Weier, T.; Uhlemann, M.; Bund, A.; Fröhlich, J.Electrochimica Acta 2010, 55, 9060–9066.(3) Karnbach, F.; Uhlemann, M.; Gebert, A.; Eckert, J.; Tschulik, K. Electrochimica Acta2014, 123, 477–484

Mid-Infrared (MIR) Complex Refractive Index Spectra of Polycrystalline Copper-Nitride Films by IR-VASE Ellipsometry and Their FIB-SEM Porosity

Copper-nitride (Cu3N) semiconductor material is attracting much attention as a potential, next-generation thin-film solar light absorber in solar cells. In this communication, polycrystalline covalent Cu3N thin films were prepared using reactive-RF-magnetron-sputtering deposition, at room temperature, onto glass and silicon substrates. The very-broadband optical properties of the Cu3N thin film layers were studied by UV-MIR (0.2–40 μm) ellipsometry and optical transmission, to be able to achieve the goal of a low-cost absorber material to replace the conventional silicon. The reactive-RF-sputtered Cu3N films were also investigated by focused ion beam scanning electron microscopy and both FTIR and Raman spectroscopies. The less dense layer was found to have a value of the static refractive index of 2.304, and the denser film had a value of 2.496. The iso-absorption gap, E04, varied between approximately 1.3 and 1.8 eV and could be considered suitable as a solar light absorber.

Synthesis and Characterization of Cu-Ni Thin Films at Different pH Baths: A Comparative Study Using XRD, XPS and Corrosion Analysis

Cu-Ni films are electrodeposited at a cathodic current of 10 mA via galvanostatic mode on ITO-coated glass substrates. It found by X-ray diffraction that the films crystalized into fcc structure with the highest intensity corresponding to (111) plane at a two-theta value of 43°. The presence of binding energy peaks at 856.57 eV, 861 eV, 933 eV, and 952 eV observed in X-ray photoelectron spectroscopy have confirmed the presence of nickel oxide/hydroxide and copper oxide/hydroxide, respectively. Tafel polarization studies conducted in 3.5 wt. % sodium chloride solution shows the shifts in Ecorr towards the positive side and decrease of Icorr with the passage of exposure time is attributed to the formation of protective oxides/hydroxides layers of Cu and Ni elements in the films.

Copper Nitride: A Versatile Semiconductor with Great Potential for Next-Generation Photovoltaics

Copper nitride (Cu3N) has gained significant attention recently due to its potential in several scientific and technological applications. This study focuses on using Cu3N as a solar absorber in photovoltaic technology. Cu3N thin films were deposited on glass substrates and silicon wafers via radio-frequency magnetron sputtering at different nitrogen flow ratios with total pressures ranging from 1.0 to 5.0 Pa. The thin films’ structural, morphology, and chemical properties were determined using XRD, Raman, AFM, and SEM/EDS techniques. The results revealed that the Cu3N films exhibited a polycrystalline structure, with the preferred orientation varying from 100 to 111 depending on the working pressure employed. Raman spectroscopy confirmed the presence of Cu-N bonds in characteristic peaks observed in the 618–627 cm−1 range, while SEM and AFM images confirmed the presence of uniform and smooth surface morphologies. The optical properties of the films were investigated using UV-VIS-NIR spectroscopy and photothermal deflection spectroscopy (PDS). The obtained band gap, refractive index, and Urbach energy values demonstrated promising optical properties for Cu3N films, indicating their potential as solar absorbers in photovoltaic technology. This study highlights the favourable properties of Cu3N films deposited using the RF sputtering method, paving the way for their implementation in thin-film photovoltaic technologies. These findings contribute to the progress and optimisation of Cu3N-based materials for efficient solar energy conversion.

Power effect on the properties of copper nitride films as solar absorber deposited in pure nitrogen atmosphere

AbstractNowadays, copper nitride (Cu3N) is of great interest as a new solar absorber material, flexible and lightweight thin film solar cells. This material is a metastable semiconductor, nontoxic, composed of earth‐abundant elements, and its band gap energy can be easily tunable in the range 1.4–1.8 eV. For this reason, it has been proposed for many applications in the solar energy conversion field. The main aim of this work is to evaluate the properties of the Cu3N thin films fabricated by reactive radio‐frequency (RF) magnetron sputtering at different RF power values to determine its potential as light absorber. The Cu3N films were fabricated at room temperature from a Cu metallic target at the RF power ranged from 25 to 200 W onto different substrates (silicon and glass). The pure nitrogen flux was set to 20 sccm, and the working pressures were set to 3.5 Pa and 5 Pa. The X‐ray diffraction results showed a transition from (100) to (111) preferred orientations when RF power increased; the atomic force microscopy images revealed a granular morphology, while Fourier transform infrared spectroscopy and Raman spectra exhibited the characteristics peaks related to Cu–N bonds, which became narrower when the RF power increased. Finally, to stablish the suitability of these films as absorber, the band gap energy was calculated from transmission spectra.

A Comparison between Porous to Fully Dense Electrodeposited CuNi Films: Insights on Electrochemical Performance.

Nanostructuring of metals is nowadays considered as a promising strategy towards the development of materials with enhanced electrochemical performance. Porous and fully dense CuNi films were electrodeposited on a Cu plate by electrodeposition in view of their application as electrocatalytic materials for the hydrogen evolution reaction (HER). Porous CuNi film were synthesized using the hydrogen bubble template electrodeposition method in an acidic electrolyte, while fully dense CuNi were electrodeposited from a citrate-sulphate bath with the addition of saccharine as a grain refiner. The prepared films were characterized chemically and morphologically by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The Rietveld analysis of the XRD data illustrates that both CuNi films have a nanosized crystallite size. Contact angle measurements reveal that the porous CuNi film exhibits remarkable superhydrophobic behavior, and fully dense CuNi film shows hydrophilicity. This is predominately ascribed to the surface roughness of the two films. The HER activity of the two prepared CuNi films were investigated in 1 M KOH solution at room temperature by polarization measurements and electrochemical impedance spectroscopy (EIS) technique. Porous CuNi exhibits an enhanced catalysis for HER with respect to fully dense CuNi. The HER kinetics for porous film is processed by the Volmer-Heyrovsky reaction, whereas the fully dense counterpart is Volmer-limited. This study presents a clear comparison of HER behavior between porous and fully dense CuNi films.

Homogenizing of Pt on NiCu films for enhanced HER activity by two-step magneto-electrodeposition

The efficient production of hydrogen through water electrolysis requires stable, high-performance and rather cost-effective electrocatalysts to promote the hydrogen evolution reaction (HER).

Amorphous NiCu Thin Films Sputtered on TiO2 Nanotube Arrays: A Noble‐Metal Free Photocatalyst for Hydrogen Evolution

AbstractIn this work, NiCu co‐catalysts on TiO2 are studied for photocatalytic hydrogen evolution. NiCu co‐catalyst films are deposited at room temperature by argon plasma sputtering on high aspect‐ratio anodic TiO2 nanotubes. To tune the Ni : Cu atomic ratio, alloys of various compositions were used as sputtering targets. Such co‐catalyst films are found to be amorphous with small nanocrystalline domains. A series of parameters is investigated, i. e., i) Ni : Cu relative ratio in the sputtered films, ii) NiCu film thickness, and iii) thickness of the TiO2 nanotube layers. The highest photocatalytic activity is obtained with 8 μm long TiO2 nanotubes, sputter‐coated with a 10 nm‐thick NiCu films with a 1 : 1 Ni : Cu atomic ratio. This photocatalyst reaches a stable hydrogen evolution rate of 186 μL h−1 cm−2, 4.6 and 3 times higher than that of Ni‐ and Cu‐TiO2, respectively, demonstrating a synergistic co‐catalytic effect of Ni and Cu in the alloy co‐catalyst film.

Comparative study of electrical properties of chalcogenide films produced by reaction of Cu, Ag, Ni and NiCu with Sb2S3 in hot wall epitaxy

Films of transition-metal–chalcogen alloys are produced using hot wall epitaxy by means of sulphurization in the exposure of Cu, Ag, Ni and NiCu films to Sb2S3 vapor. The properties of the resultant chalcogenide films change widely depending on the material combination and the synthesis conditions. We investigate the influences of the coexistence of Sb in the alloys on the electrical properties of the films. The Ni-containing films are highly conductive, whereas the resistivity of the films produced from Cu and Ag is large. The sulphurization occurs two-dimensionally as homogeneous films consisting of Cu-Sb-S and Ag-Sb-S ternary alloys, giving rise to weak and negligible dependencies of the resistivity on the synthesis temperature in the respective cases. The thermal activation energy for the electrical transport varies in correspondence to the resistivity values. The Cu- and Ag-based films exhibit a suppression of current when Ag electrodes are used in comparison to using Au electrodes. The transient of photocurrent is shown for these films to be remarkably slow with an order of magnitude change of the current. The spontaneous reaction with Al contacts to trigger interfacial resistance switching is weak for the Sb-containing materials. The structural properties of the films are furthermore presented together with the Raman spectra to identify the synthesized alloys. A catalytic effect of Ni in the sulphurization of Cu and the surfactant effect of Sb are thereby revealed.

Enhanced Electrical Properties of Copper Nitride Films Deposited via High Power Impulse Magnetron Sputtering.

High Power Impulse Magnetron Sputtering (HiPIMS) has generated a great deal of interest by offering significant advantages such as high target ionization rate, high plasma density, and the smooth surface of the sputtered films. This study discusses the deposition of copper nitride thin films via HiPIMS at different deposition pressures and then examines the impact of the deposition pressure on the structural and electrical properties of Cu3N films. At low deposition pressure, Cu-rich Cu3N films were obtained, which results in the n-type semiconductor behavior of the films. When the deposition pressure is increased to above 15 mtorr, Cu3N phase forms, leading to a change in the conductivity type of the film from n-type to p-type. According to our analysis, the Cu3N film deposited at 15 mtorr shows p-type conduction with the lowest resistivity of 0.024 Ω·cm and the highest carrier concentration of 1.43 × 1020 cm−3. Furthermore, compared to the properties of Cu3N films deposited via conventional direct current magnetron sputtering (DCMS), the films deposited via HiPIMS show better conductivity due to the higher ionization rate of HiPIMS. These results enhance the potential of Cu3N films’ use in smart futuristic devices such as photodetection, photovoltaic absorbers, lithium-ion batteries, etc.

Effective Exchange Energy in a Thin, Spatially Inhomogeneous CuNi Layer Proximized by Nb.

Thin films of diluted magnetic alloys are widely used in superconducting spintronics devices. Most studies rely on transport measurements and assume homogeneous magnetic layers. Here we examine on a local scale the electronic properties of the well-known two-layer superconductor/ferromagnet structure Nb/CuNi. Scanning tunneling spectroscopy experiments demonstrated significant spatial variations of the tunneling conductance on nanoscale, with characteristic gapped, nongapped, and strongly zero-bias peaked spectra. The microscopic theory successfully reproduced the observed spectra and relied them to spatial variations of CuNi film thickness and composition, leading to strong variations of the effective exchange energy. The observed inhomogeneities put constraints on the use of diluted magnetic alloys in nanoscale devices.

Electrochemically Fabricated Surface-Mesostructured CuNi Bimetallic Catalysts for Hydrogen Production in Alkaline Media.

Ni-based bimetallic films with 20 at.% and 45 at.% Cu and mesostructured surfaces were prepared by electrodeposition from an aqueous solution containing micelles of P123 triblock copolymer serving as a structure-directing agent. The pH value of the electrolytic solution had a key effect on both the resulting Cu/Ni ratio and the surface topology. The catalytic activity of the CuNi films toward hydrogen evolution reaction was investigated by cyclic voltammetry (CV) in 1 M KOH electrolyte at room temperature. The Cu45Ni55 film showed the highest activity (even higher than that of a non-mesostructured pure Ni film), which was attributed to the Ni content at the utmost surface, as demonstrated by CV studies, as well as the presence of a highly corrugated surface.