Cu3N Films Research Articles

Time-resolved photoresponse of nanometer-thick Nb/NiCu bilayers

We present femtosecond optical time-resolved pump-probe investigations of superconducting hybrids structures consisting of Nb/NiCu bilayers with various thickness. Measurements performed on pure Nb and NiCu films are also given. The photoresponse experiments provide the quasiparticle relaxation times in bilayers of different thickness ratios. The study of the photoresponse as a function of the temperature reveals the spatial evolution of the superconductor order parameter across the bilayers.

Reactive magnetron sputtering of copper, silver, and gold

Copper, silver, and gold targets were sputtered in various reactive gas mixtures (Ar–N2, Ar–O2, and Ar–CH4) to compare the reactivity of noble metal atoms during the sputtering process. The evolution of the film's growth rate and the variation of the reactive gas partial pressure vs. the reactive gas flow rate were investigated for each kind of metal. The structure of the deposited films was characterised by X-ray diffraction. Electrical resistivity of the coatings was determined at room temperature. The optical band gap of oxides and nitrides films were deduced from UV–visible transmission measurements. The reactive sputtering of copper target leads to the synthesis of Cu3N, Cu2O, Cu4O3, or CuO films. No copper carbide films were deposited. Depending on the methane flow rate, Cu/C films were either nanocomposite coatings (nc-Cu/a-C:H) or amorphous. Silver oxide (Ag2O) films were formed by reactive sputtering of a silver target in Ar–O2 mixtures. On the other hand, the reactive sputtering method did not allow the synthesis of silver nitride nor gold oxide films.

Study on the preparation and properties of copper nitride thin films

Copper nitride (Cu3N) thin films were prepared on glass substrates by reactive radio-frequency (RF) magnetron sputtering under different nitrogen flow rate. The thermal stability of the Cu3N films was investigated through vacuum annealing treatment at different temperature. X-ray diffraction, scanning electron microscopy and near-normal reflectance spectra were employed to characterize the films. The deposited Cu3N films take on a different preferred orientation, which changed from (111) to (100) with increase of N2 ratio. The grains size of thin films can become small when the N2 ratio increases. The Cu3N phase can completely decompose into Cu and N2 through vacuum annealing treatment at a temperature of 200°C. The reflectance of as-deposited Cu3N films is quite different from decomposed films.

Electrodeposition and Characterization of Nickel-Copper Alloy Films as Electrode Material in Alkaline Media

A new and simple electrochemical procedure of anodic codeposition of nickel and copper oxide-hydroxide species on the gold electrode substrate from alkaline solutions is described. The electrodeposited alloy film, with an average composition Ni:Cu of 0.67 (i.e., was investigated by electrochemical, scanning electron microscopy, and X-ray photoelectron spectroscopy techniques. The resulting deposited alloys appear uniform, smooth, adherent to the gold substrate, and homogeneous, independently of the electrochemical procedure adopted for the preparation (i.e., potentiostatic or potentiodynamic conditions). The presence of copper oxyhydroxide species in deposited film imparts an extensive stabilization of the β/β crystallographic forms of the nickel oxyhydroxide under prolonged repetitive potential cycling in alkaline medium. The electrocatalytic activity of the resulting composite Ni-Cu film was investigated toward the oxidation of carbohydrates using glucose as a model compound. © 2002 The Electrochemical Society. All rights reserved.

X-ray microanalysis of multi-elements coatingsusing Auger formalism: application to biomaterials

For the thickness determination of thin coatings on substrate in scanning electron microscopy using x-ray energy dispersive spectrometry, a method called Auger formalism has been established in our laboratory. It consists of applying a formalism derived from that in the Auger spectroscopy which assumes a linear relationship between the signal intensity emitted by the coating and its thickness.In this paper, a development of the Auger formalism in the case of heterogeneous coatings is presented. Using x-ray energy dispersive spectrometry, this method allows one to determine the atomic concentrations of the elements which composed the coating. The capability of the proposed method is illustrated by two different applications: a Ni-Cu film on titanium alloy substrate (academic specimen) and calcium phosphate film on titanium alloy substrate (prosthetic coating). An iterative procedure established for the proposed method is also presented. The results show that the Auger formalism may now be applied not only to simple coatings for thickness determination but also to the complex ones for concentration determination. And its use does not require the local knowledge of the substrate composition which is not accessible in the Auger spectroscopy.

New CuM2/3Sb1/3O2 and AgM2/3Sb1/3O2 compounds with the delafossite structure

Abstract Several new compounds have been prepared with the delafossite structure: CuMn 2/3 Sb 1/3 O 2 , CuCo 2/3 Sb 1/3 O 2 , CuNi 2/3 Sb 1/3 O 2 , CuZn 2/3 Sb 1/3 O 2 , CuMg 2/3 Sb 1/3 O 2 , AgNi 2/3 Sb 1/3 O 2 , and AgZn 2/3 Sb 1/3 O 2 . The structures of the CuM 2/3 Sb 1/3 O 2 compounds are generally based on 2H stacking along the c axis, and the M 2+ and Sb 5+ cations can be ordered or disordered. The structures of the AgM 2/3 Sb 1/3 O 2 compounds are based on 3R stacking along c with the M 2+ and Sb 5+ cations disordered. The structures of CuMn 2/3 Sb 1/3 O 2 (disordered) and CuMg 2/3 Sb 1/3 O 2 (ordered) were refined from single crystal X-ray diffraction data. Pellets and transparent thin films of CuNi 2/3 Sb 1/3 O 2 with 10% Sn doping for Sb showed p-type electronic conduction.

Growth and properties of Cu3N films and Cu3N/γ′-Fe4N bilayers

Copper nitride films were grown by molecular-beam epitaxy of copper in the presence of nitrogen from a radio-frequency atomic source on (001) γ′-Fe4N/(001)MgO or directly on MgO substrates. The structural properties of the Cu3N films were found to be very dependent on the substrate and on the deposition temperature. At optimal growth conditions, the Cu3N films grow epitaxial on both substrates. The Cu3N films grown on MgO were characterized optically to be insulators with an energy gap of 1.65 eV. On γ′-Fe4N, Cu3N films with a thickness of only 6 nm, were grown as closed layers, epitaxial and rather smooth (root-mean-square roughness of 0.7 nm). This material has ideal properties to be used as a barrier in low resistance magnetic tunnel junctions.

Oxidation, Diffusion and Segregation in CuNi(Mn) Films Studied by AES

The surface and in-depth compositions of sputter-deposited Cu0.57Ni0.42Mn0.01 thin films were studied by Auger electron depth profiling after thermal treatment. The samples were thermally cycled to maximum temperatures of 300 °C to 550 °C in air, argon and forming gas (N2, 5 vol. % H2). Linear least-squares fit to standard spectra and factor analysis were applied to separate the overlapping Auger transitions of Cu and Ni. Under bombardment by 4 keV argon ions, CuNi(Mn) layers display bombardment-induced surface enrichment of Ni in the same extent as binary CuNi alloys. At sufficiently high oxygen partial pressures, a duplex oxide layer is formed and a thick surface copper oxide overgrows the initial nickel oxide. In reducing atmosphere selective oxidation of manganese takes place. A capping NiCr layer prevents CuNi(Mn) from being oxidized, but the film configuration is degraded with increasing annealing temperature due to formation of a surface chromium oxide and diffusion of Ni from the CuNi(Mn) layer into the NiCr/CuNi(Mn) interface.

Deposition and Characterization of Metastable Cu 3 N Layers for Applications in Optical Data Storage

Cu3N films for optical data storage were deposited on Si(100) wafers and 0.6 mm thick polycarbonate DVD base material discs at a temperature of 50 °C by reactive magnetron sputtering. A copper target was sputtered in rf mode in a nitrogen plasma. For basic investigations concerning the composition and structure of Cu3N, Si wafers were used as substrate material. To study the suitability of Cu3N as an optical data storage medium under technical conditions, Cu3N/Al bilayers were deposited on polycarbonate discs. The composition and structure of the films were investigated by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD).

Preparation of Cu-Ni Film Resistors with Low Resistivity and Low TCR

SUMMARYThin film resistors with low TCR and low electric resistivity were prepared from phosphorus free Cu-Ni alloy obtained by electroless and electrolytic deposition with heat treatment at low temperature.

Deformation-Mechanism Map for CuNi Thin Films

Deformation-mechanism maps have been constructed for Cu0.6Ni0.4 thin films using strain-rate equations for bulk material with some thin-film adaptations, and literature data for the diffusivities. Differences between the constructed maps and the results of thermal cycling of CuNi films arise mainly by too low estimated yield stresses and yield limits for diffusional flow due to the attachment of the film onto the substrate.

Copper nitride thin films prepared by the RF plasma chemical reactor with low pressure supersonic single and multi-plasma jet system

The RF plasma chemical reactor with low pressure supersonic plasma jet system (RPJ) has been used for deposition of Cu3N thin films. From comparison of experimental values of composition weight per cent with theoretically predicted ones, and from XRD analysis, it follows that if the RF power absorbed in the reactor does not exceed 75 W, stoichiometric Cu3N films are achieved. The typical value of deposition growth rate was found to be on the order of 16 nm/min for RF power Pw≈40 W. The optical energy gap Eg and microhardness H of the deposited Cu3N thin films increased with decreasing RF power. They are Eg=1.24 eV and H=8.8 GPa for the sample deposited at RF power 40 W. For RF power higher than approximately 75 W, it appears that a small amount of Cu microparticles, up to ∼1 μm, is diluted in the Cu3N film. The deposition of the microparticles can be explained by local overheating of the probe surface by RF power absorbed in RF hollow cathode discharge.

Cu3N films prepared by the low-pressure r.f. supersonic plasma jet reactor: Structure and optical properties

Abstract A low-pressure r.f. supersonic plasma jet reactor (RPJ) has been used for deposition of Cu3N thin films. From a comparison of experimental values of composition weight per cent with the theoretically predicted values, it follows that if the r.f. power absorbed in the reactor does not exceed 75 W, stoichiometric Cu3N films can be obtained. The typical value of the deposition growth rate was found to be in the order of 16 nm min−1 for r.f. power Pw≈40 W. The optical energy gap, Eg, microhardness, H, and Young's modulus, E, of the deposited Cu3N thin films increase with decreasing r.f. power. They are Eg=1.24 eV, H=8.8 GPa and E=146 GPa for the sample deposited with a r.f. power of 40 W. Deposition of Cu3N thin films by means of the modificated RPJ reactor (with a multi-jet system) on to internal walls of cavities, holes and on the surface of complex shapes of hollow substrates can be useful for surface-treatment technology.

Copper nitride thin films prepared by reactive radio-frequency magnetron sputtering

Copper nitride (Cu3N) thin films were deposited on glass substrates by reactive radio-frequency (rf) magnetron sputtering from a metal copper target in a nitrogen/argon atmosphere. The deposition rate of the films gradually decreased and excessive nitrogen was added to the films as nitrogen partial pressure increased. The color of the deposited films was a reddish dark brown. The Cu3N films obtained by this deposition method were strongly textured with crystal direction[100]. The grain size of the polycrystalline films ranged from 15 to 30 nm. The resistivity and the optical energy gap of the films were found to be change with the nitrogen content.

Mechanical Stress, Grain-boundary Relaxation, and Oxidation of Sputtered CuNi(Mn) Films

This paper focuses on understanding stress development in CuNi42Mn1 thin films during annealing in Ar. In addition to stress-temperature measurements, resistance-temperature investigations and chemical and microstructural characterization by Auger electron spectroscopy, scanning and transmission electron microscopy, x-ray diffraction, and atomic force microscopy were also carried out. The films are polycrystalline with a grain size of 20 nm up to 450 °C. To explain the stress evolution above 120 °C, atomic rearrangement (excess-vacancy annihilation, grain-boundary relaxation, and shrinkage of grain-boundary voids) and oxidation were considered. Grain-boundary relaxation was found to be the dominating process up to 250–300 °C. A sharp transition from compressive to tensile stress between 300 and 380 °C is explained by the formation of a NiO surface layer due to reaction with the remaining oxygen in the Ar atmosphere. This oxidation is masking the inherent structural relaxation above 300 °C.

Young's modulus and tensile strength of CuNi(Mn) thin films on polyimide foils by tensile testing

Force-strain curves were measured for 1.0 μm and 1.5 μm thick Cu0.57Ni0.42Mn0.01 films on 8 μm thick polyimide foils by tensile testing. By separating the force working on the polyimide foil from that working on the metal-polyimide compound, stress-strain curves for the CuNi(Mn) films were obtained. Young's modulus and tensile strength were determined for as-deposited and annealed [350 °C, 1 h, N2/H2(5 vol%) atmosphere] films by this method. Crack propagation starts at the end of the elastic region at 0.2 to 0.7% strain, depending on the film thickness and the thermal treatment. The cracking behavior is described by a steady-state approximation.

Properties of various sputter-deposited Cu–N thin films

Compositions and structures of sputter-deposited Cu–N films are strongly dependent on the total sputtering pressure and on the content of nitrogen gas. The Cu–N films obtained can be classified into four categories: metallic Cu-rich Cu3N films with a positive temperature coefficient of resistivity (TCR), semiconducting Cu-rich Cu3N films, semiconducting stoichiometric Cu3N films, and semiconducting N-rich Cu3N films with a negative TCR. The current–voltage curves of various Cu–N films are presented. The metallic conduction and semiconductor conduction are two main electrical conduction mechanisms for various Cu–N films. The decomposition temperature of various Cu–N films has been determined to be around 604–614 K using both thermogravimetry and dynamical measurement of electrical resistance during heating in a vacuum furnace. The great scattering of data over the electrical resistivity of Cu3N reported up to now is mainly due to the nonstoichiometry of the Cu3N. The optical band gap of stoichiometric Cu3N is determined to be around 1.8–1.9 eV, but it decreases with the decrease in the degree of stoichiometry.

The Mechanical Response of Thin Film Substrates Subject to Ultrasonic Joining

ABSTRACTThe ultrasonic wire bonding process is widely used for making interconnections between IC chips and package lead frames, yet the relationships between the wire/substrate materials properties and the bond formation processes are not yet well understood. In this study, we have conducted experiments to understand the mechanical response in thin film substrates subject to ultrasonic wire bonding. Atomic force microscopy (AFM) has been used to examine the morphology of thin film surfaces before and after bonding. Al wires were bonded to thin films of Cu, Cu-Ni and Ag, after which the aluminum wire was removed by etching. AFM examination of the Cu and Cu-Ni bonded surfaces revealed the extent of surface smoothing increased with bonding power level. However, at power levels typically employed in practice almost no morphological surface changes were observed, indicating surface smoothing is not required to obtain good bonds. TEM and SEM cross-sections were also used to examine Al wedge bonds and Au ball bonds to Al films on Si. A wide variety of features were observed, including surface smoothing, microcracking and void formation.

Development of Mechanical Stress in Cuni(mn) Films During Temperature Ramping: Related Mechanisms

ABSTRACTThis paper focusses on the development of biaxial stress in Cu0.57Nio.42Mno.ol thin films during annealing in Ar and, for comparison, in vacuum. Besides stress-temperature measurements also resistance-temperature investigations as well as chemical and microstructural characterization by Auger electron spectroscopy, scanning and transmission electron microscopy, and X-ray diffraction were carried out. To explain the stress evolution, atomic rearrangement (excessvacancy annihilation, grain-boundary relaxation, and shrinkage of grain-boundary voids) and oxidation were considered. Up to 250 - 300 °C grain-boundary relaxation was found to be the dominating process. A sharp transition from compressive to tensile stress between 300 °C and 380 °C is explained by the formation of a NiO surface layer

Stress-Strain Curves by Tensile Testing of Thin Metallic Films On Thin Polyimide Foils: Al, AlCu, CuNi(Mn)

ABSTRACTFor better understanding the mechanical properties of thin films it is helpful to use the same experimental methods as for bulk material, like tensile tests, thereby being able to directly compare the results. However, tensile tests of free-standing metallic thin films are often difficult to perform for reasons of preparation, handling, and stresses in the films. By leaving the metallic film on an elastic substrate tensile tests were performed in a rather simple and precise manner, using a commercial tensile testing machine. Stress-strain curves were determined by separating the force working on the substrate from that working on the film-substrate compound. Those measurements were done at room temperature for Al, AlCu(0. 5 wt %) and Cuo0.57Ni0.42Mn0.01 thin (200–2000 nm) films prepared by magnetron sputtering on 8 μm and 13 μm thick polyimide (Kapton) foils. The film microstructure was characterized by scanning and transmission electron microscopy and X-ray diffraction. The tensile strength of the fine grained films was found to be up to one order of magnitude higher than for the corresponding coarse grained bulk material. Al and AlCu films showed little, CuNi(Mn) films showed no plastical behavior. Crack formation started between 0.3 % and 2 % strain depending on the material, the thermal history, and the grain size.