Thin Cu Films Research Articles

Cu thin film growth on stepped Si substrate: Effects of incident energy and thermal annealing

The existence of defects on the substrate surface is unavoidable and has a significant impact on the determination of surface properties. Among the prevalent types of defects, steps play an important role. In this study, molecular dynamics simulations are employed to explore the growth process of a thin film of Cu on a Si (001) substrate with a step. This research investigates how incident energy and thermal annealing affect the growth mode, surface roughness, film-substrate interface, and dislocation evolution. The results indicate that during the initial stage of the growth, the nucleation phenomenon was observed on terraces. The simulation indicates that the Cu atoms occur in an island growth mode on the stepped substrate. It is found that when the incident energy is increased and thermal annealing is performed, the surface curvature and roughness are reduced. Furthermore, the intermixing thickness at the interface increases due to the variation of the incidence energy. A dislocation analysis revealed that some dislocations disappeared before and after annealing, and a perfect dislocation appeared by increasing the incident energy.

Composition-Tunable Properties of Cu(Ag) Alloy for Hybrid Bonding Applications

In the present study, the properties of Cu(Ag) alloy films were studied to evaluate their potential use as an alternate material for interconnection in hybrid bonding. Thin alloy films of Cu(Ag) were deposited by pulsed electrochemical deposition (PED) using a sulfuric acid-based bath, rotating disk electrode, and hot entry. Secondary ion mass spectrometry (SIMS) was used to measure the silver content of the films, with us finding that it decreases with increasing duty cycle. Thereafter, bright field scanning transmission electron microscope (STEM) imaging in combination with energy-dispersive x-ray spectroscopy (EDS) was used to visualize the thin film microstructure and to confirm the uniform distribution of silver throughout the film, with no bands being seen despite the pulsed nature of the deposition. Film resistance was measured by a four-point probe to quantify the impact of Ag content on resistivity, with us finding the expected linear relationship with the Ag content in the film. Furthermore, the coefficient of thermal expansion (CTE) of the films was measured using X-ray diffraction, and modulus and hardness were measured via nanoindentation, revealing linear dependences on the Ag content as well. Notably, the addition of 1.25 atom% Ag resulted in a significant increase in the CTE from 17.9 to 19.3 ppm/K, Young’s modulus from 111 to 161 GPa, and film hardness from 1.70 to 3.99 GPa. These simple relationships offer a range of properties tunable via the duty cycle of the pulsed plating, making Cu(Ag) a promising candidate for engineering wafer-to-wafer metal interconnections.

EMI Shielding and Conductive Textiles Functionalized with (Ti,Cu) Nanomaterials for Biomedical Applications.

This study explores the potential of integrating thin-film technology in the design of new and effective electromagnetic interference (EMI) shielding and conductive materials for textiles and wearables. This application is of particular interest to the textile industry as it can bring new functionalities to wearables and protect humans from prolonged exposure to EM radiation. Three different thin films of pure Ti, pure Cu, and Ti-doped with Cu prepared by magnetron sputtering were used to functionalize textile knits based on cotton (code 39F) and lyocell fibers (62I). The films displayed different crystalline structures, morphologies, and topographies, which depended on their chemical compositions. The shielding effectiveness (SE) of the functionalized knits against EMI was evaluated in the frequency range of 2-8 GHz. Also, the electrical response under stress was assessed since the electrical conductivity is closely related to the EMI shielding effectiveness. The results demonstrate the feasibility of using a thin conductive layer based on Cu or Ti-Cu to improve the shield textiles with great adhesion and low thickness, providing an interesting path to improve shielding efficiency for EMI without modifying the flexibility of the textiles.

Durability and Surface Oxidation States of Antiviral Nano-Columnar Copper Thin Films.

Antiviral coatings that inactivate a broad spectrum of viruses are important in combating the evolution and emergence of viruses. In this study, nano-columnar Cu thin films have been proposed, inspired by cicada wings (which exhibit mechano-bactericidal activity). Nano-columnar thin films of Cu and its oxides were fabricated by the sputtering method, and their antiviral activities were evaluated against envelope-type bacteriophage Φ6 and non-envelope-type bacteriophage Qβ. Among all of the fabricated films, Cu thin films showed the highest antiviral activity. The infectious activity of the bacteriophages was reduced by 5 orders of magnitude within 30 min by the Cu thin films, by 3 orders of magnitude by the Cu2O thin films, and by less than 1 order of magnitude by the CuO thin films. After exposure to ambient air for 1 month, the antiviral activity of the Cu2O thin film decreased by 1 order of magnitude; the Cu thin films consistently maintained a higher antiviral activity than the Cu2O thin films. Subsequently, the surface oxidation states of the thin films were analyzed by X-ray photoelectron spectroscopy; Cu thin films exhibited slower oxidation to the CuO than Cu2O thin films. This oxidation resistance could be a characteristic property of nanostructured Cu fabricated by the sputtering method. Finally, the antiviral activity of the nano-columnar Cu thin films against infectious viruses in humans was demonstrated by the binding inhibition of the SARS-CoV-2 spike protein to the angiotensin-converting enzyme 2 receptor within 10 min.

Method for extracting the intrinsic diffusion coefficient from grain boundary diffusion depth profile

Numerical research is done on grain boundary diffusion of Cu-Ni bilayer thin films. Together, the composition-dependent interdiffusion coefficient and the position of the grain boundary are considered. Fick’s second law provides a quantitative assessment of the effects of grain size, volume, grain boundary diffusion coefficient, diffusion temperature, and time on the depth profile. Regarding the situation where the plateau values of the Ni concentration in the Cu layer and the Cu concentration in the Ni layer are almost the same for the case where the Ni intrinsic diffusion coefficient is significantly bigger than that for Cu, a detailed explanation is provided. We may produce a profile that is like the direct volume diffusion profile with a relative inaccuracy of 7.53% by using a method that is provided to eliminate the impacts of grain boundaries and grain size on the grain boundary diffusion profile. For most of the circumstances covered in this study, the technique is effective. The transformation of the grain boundary diffusion profile yields a composition-dependent interdiffusion coefficient, and the calculation’s outcome is consistent with the theoretical conclusion drawn from the Darken equation. Thin films of Cu (150 nm)/Ni (150 nm)/SiOx/Si (100 nm) were produced as examples, and Auger electron spectroscopy was used to determine the respective depth profiles. The calculated diffusion parameters, namely, the pre-exponential factor and the activation energy, are well within the bounds of the available data.

A comparison of antibacterial activity in dark-UV light in perspective of surface and structural properties of spray pyrolysis grown Cu doped Cr2O3 thin films

Thin films of Cr2O3 and Cu doped Cr2O3 thin films were prepared using the spray pyrolysis technique with different Cu/Cr ratios. Precursor solution of 0.2 M was sprayed on a pre-heated (≈ 400 °C) soda lime glass substrate using air as the carrier gas. XRD analysis confirmed polycrystalline nature of the films with rhombohedral structure. Crystallite size and lattice strain have been estimated using Williamson-Hall method. These films were porous and presented a rough morphology and showed a strong signature on the presence of vibrational Cr-O bonding. The solid-liquid surface contact angle measurements revealed a large contact angle which is indicative of reduced surface energy. Vickers hardness measurement reveals that Cr2O3 thin film with 2% Cu/Cr ratio have high hardness value of 903 HV (0.2 kgf). The antibacterial activity of the films was investigated against two gram-positive (Bacillus Subtilus and Bacillus Meurellus) and two gram-negative bacteria (Escherichia Coli and Acetobacter Rhizopherensis). A comparison was established both under dark and UVA light in terms of structural properties of the films. Antibacterial activity was significantly enhanced with the increase in Cu/Cr ratio. Interestingly, the UVA light further facilitated to boost the antibacterial effect against both types of bacteria. A good correlation was found between the structural parameters and the zone of inhibition.

Stress-induced pseudoelasticity in freestanding Cu–Al–Ni thin film by AFM-assisted nanoindentation

Freestanding thin films of Cu–Al–Ni shape memory alloys (SMAs) have attracted interests in recent years for the development of next generation micro-scaled sensors and actuators in MEMS. Thin films’ capacity to recover stress-induced strain is critical to assess their potential for applications in these technologies. In this work, we report for the first time a quantitative study of this capacity in a freestanding Cu–Al–Ni thin film by Atomic Force Microscopy (AFM)-assisted nanoindentation. Stress-induced pseudoelastic (or superelastic) effects were successfully observed by this technique for relatively high strains up to a relative indentation depth of 30% concerning the film thickness. This effect highlights a clear shape memory effect, suggesting a sample's high mechanical performance for potential applications in the design of micro actuators for MEMS technologies. Results enable to set new perspectives of the use of this technique as an efficient methodology for future study of pseudoelasticity in micro/nanostructured SMAs.

Stress tuning in sputter-grown Cu and W films for Cu/W nanomultilayer design

Controlling growth stresses during thin film fabrication is of paramount importance to solve reliability issues during operation of functional thin films in harsh environments. A combination of different methods for thin-film stress determination, such as in situ wafer curvature and ex situ x-ray diffraction, is usually required to reveal and tailor growth stresses in thin film systems, as well as to extract interface stress contributions in multilayered coatings. In this article, the tuning of intrinsic growth stresses in thin films of Cu and W, as grown by magnetron sputtering, was performed by varying the Ar pressure and gun power during thin-film deposition. The average growth stress in Cu and W thin films could be tuned between tensile and compressive. Next, the thus obtained knowledge on stress engineering of Cu and W single layers was applied to investigate the corresponding intrinsic stresses in Cu/W nanomultilayer coatings, for which interface stress was found to play an important role.

Effects of ammonia concentration on morphology, composition and optical properties of ZnO1-xSx thin films of Cu(In, Ga)Se2 solar cells

Effects of ammonia concentration on morphology, composition and optical properties of ZnO1-xSx thin films of Cu(In, Ga)Se2 solar cells

Plasmon resonance-induced photoluminescence enhancement of CdS quantum dots thin films on fabricated Au/Ag/Cu metallic thin films

Multi-metallic nanoparticles (NPs) offer tunable Localized Surface Plasmon Resonance properties which depend on their elemental and configurational variations, which have been used in optical sensing and biomedical imaging. In the present study, the composition and optical properties of hybrid nano-structured thin films of CdS quantum dots (QDs) incorporated on Au-, Ag- and Cu-NPs for photonic applications are investigated. Initially, CdS QDs were prepared by chemical reduction method and characterized by Transmission electron microscopy, UV–Visible absorption spectroscopy and Fourier transform infrared spectroscopy techniques. Then nanometer thin films of Au, Ag and Cu were fabricated by thermal evaporator and insitu heating along with uniform rotation of substrate was used to convert these into respective uniform spherical NPs on ITO substrate. Further, CdS QDs were deposited over these metallic NPs and we observed enhanced photoluminescence (PL) of CdS QDs due to Surface Plasmon Resonance effect by these metallic NPs. The time resolved spectroscopy of these films was carried out to correlate the enhanced PL emission from CdS–Au–Ag–Cu-ITO thin film. The results of the present study of these plasmonic nanostructures will be further utilized in metal enhanced fluorescence sensors.

Irradiation of Cu(In, Ga)Se-=SUB=-2-=/SUB=- Thin Films by 10 MeV Electrons at 77 K: Effect on Photoluminescence Spectra

Thin films of Cu(In, Ga)Se2 on Mo/glass were irradiated by 10 MeV electrons at 77 K and examined by photoluminescence at 77 K before and after irradiation without warming the samples as well as after warming to 300 K. The photoluminescence spectra revealed a broad band constituting 3 merged peaks (P1, P2, P3) assigned to: band-to-band recombination (P1) and recombination of free electrons with holes localised at acceptors influenced by the valence band tail (P2, P3). Irradiation reduced the intensity of the peaks due to deep traps generated by electrons and anomalously reduced the degree of compensation of the material. Keywords: thin films, irradiation, photoluminescence, recombination, band-to-band.

Irradiation of Cu(In, Ga)Se-=SUB=-2-=/SUB=- Thin Films by 10 MeV Electrons at 77 K: Effect on Photoluminescence Spectra

Thin films of Cu(In,Ga)Se2 on Mo/glass were irradiated by 10 MeV electrons at 77 K and examined by photoluminescence at 77 K before and after irradiation without warming the samples as well as after warming to 300 K. The photoluminescence spectra revealed a broad band constituting 3 merged peaks (P1, P2, P3) assigned to: band-to-band recombination (P1) and recombination of free electrons with holes localised at acceptors influenced by the valence band tail (P2, P3). Irradiation reduced the intensity of the peaks due to deep traps generated by electrons and anomalously reduced the degree of compensation of the material. Keywords: thin films, irradiation, photoluminescence, recombination, band-to-band.

Optical and microstructural characterization of nanocrystalline Cu doped ZnO diluted magnetic semiconductor thin film for optoelectronic applications

A series of Zn 1-x Cu x O nanocrystalline films were deposited on a silica substrate using e-beam evaporation technology. The physical properties of the deposited film were closely examined using x-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), atomic force microscopy (AFM), and spectroscopic ellipsometry (SE). The deposited film's structure revealed the formation of a hexagonal wurtzite structure, with no extra phases found. According to AFM analysis, the deposited Zn 1-x Cu x O (x = 0.0, 0.04, 0.08, 0.12, 0.16, and 0.2) film has nanocrystalline characteristics. The present findings show that increasing Cu content up to x ≤ 0.2 reduces the direct optical energy gap E g from 3.286 eV (x = 0) to 2.934 eV (x = 0.2), which can be attributed to the sp-d exchange coupling. The refractive index dispersion extracted from SE analysis for Cu-doped ZnO thin films increased as the Cu dopant increased. In addition, the refractive index dispersion of the deposited film was studied using a single oscillator model proposed by Wemple-DiDomenico (WDD). It was found that the oscillator energy E o decreases as the Cu concentration increases, while the dispersion energy E d increases. As a result of the improvement in the optical energy band gap and the tunability of the values of the dispersive oscillator parameters E o , E d , n 0 , ε 0 , M -1 , and M -3 with increasing Cu doping levels, Cu doped ZnO films are a good candidate for optoelectronic device applications. • E-beam techniques is used to deposit a series of thin film of Cu doped ZnO. • The deposited film's structure show the formation of a hexagonal wurtzite structure. • SE technique is used to obtained the direct energy gap and found that E g is reduced from 3.286eV to 2.934eV with Cu concentration increases from 0 up to 0.2. • The SE analysis reveal that refractive index dispersion of Cu-doped ZnO thin films has increased as the Cu dopant has increased.

Fabrication NiO: Cu / Si Heterojunction by the Aerosol-Assisted Chemical Vapor Deposition (AACVD)

In this research, as the thin films were formed by an AACVD process, copper doped nickel oxide was used to prepare the Cu doped Ni thin films by ratio doping (Cu/Ni = 0, 7.5, 10 and 12.8 at w.t %). Thin films of Cu doped NiO were heated at a crystallization temperature of 400 °C for 2 hours. The thin films obtained by the AACVD method have a film thickness of the order (45-62 nm). Promising solar cells that could be created by NiO film as the absorber using Cu doping. The NiO:Cu film has promising optical characteristics; about (3.5-2.8 eV) energy gap band and a high absorption coefficient, which means that the most suitable absorber can be commercially developed using the NiO:Cu film. Furthermore, there are no rare metals in the NiO: Cu film The best conversion efficiency with the heterojunction of NiO: Cu/Si and NiO:Cu was 2.8571429% which showed the possibility of a very low cost solar cell.

A Hybrid Hole Transport Layer for Perovskite-Based Solar Cells

This paper presents the effect of a composite poly(3,4-ethylenedioxythiophene) polystyrene sulfonate PEDOT:PSS and copper-doped nickel oxide (Cu:NiOx) hole transport layer (HTL) on the performance of perovskite solar cells (PSCs). Thin films of Cu:NiOx were spin-coated onto fluorine-doped tin oxide (FTO) glass substrates using a blend of nickel acetate tetrahydrate, 2-methoxyethanol and monoethanolamine (MEA) and copper acetate monohydrate. The prepared solution was stirred at 65 °C for 4 h and spin-coated onto the FTO substrates at 3000 rpm for 30 s in a nitrogen glovebox. The Cu:NiOx/FTO/glass structure was then annealed in air at 400 °C for 30 min. A mixture of PEDOT:PSS and isopropyl alcohol (IPA) (in 1:0.05 wt%) was spun onto the Cu:NiOx/FTO/glass substrate at 4000 rpm for 60 s. The multilayer structure was annealed at 130 °C for 15 min. Subsequently, the perovskite precursor (0.95 M) of methylammonium iodide (MAI) to lead acetate trihydrate (Pb(OAc)2·3H2O) was spin-coated at 4000 rpm for 200 s and thermally annealed at 80 °C for 12 min. The inverted planar perovskite solar cells were then fabricated by the deposition of a photoactive layer (CH3NH3PbI3), [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and a Ag electrode. The mechanical behavior of the device during the fabrication of the Cu:NiOx HTL was modeled with finite element simulations using Abaqus/Complete Abaqus Environment CAE. The results show that incorporating Cu:NiOx into the PSC device improves its density–voltage (J–V) behavior, giving an enhanced photoconversion efficiency (PCE) of ~12.8% from ~9.8% and ~11.5% when PEDOT:PSS-only and Cu:NiOx-only are fabricated, respectively. The short circuit current density Jsc for the 0.1 M Cu:NiOx and 0.2 M Cu:NiOx-based devices increased by 18% and 9%, respectively, due to the increase in the electrical conductivity of the Cu:NiOx which provides room for more charges to be extracted out of the absorber layer. The increases in the PCEs were due to the copper-doped nickel oxide blend with the PEDOT:PSS which enhanced the exciton density and charge transport efficiency leading to higher electrical conductivity. The results indicate that the devices with the copper-doped nickel oxide hole transport layer (HTL) are slower to degrade compared with the PEDOT:PSS-only-based HTL. The finite element analyses show that the Cu:NiOx layer would not extensively deform the device, leading to improved stability and enhanced performance. The implications of the results are discussed for the design of low-temperature solution-processed PSCs with copper-doped nickel oxide composite HTLs.

Structural Characteristics and Photoluminescence of Thin Films of Cu(In1–xgax)(Syse1–y)2 Solid Solutions

The phase composition and structural and optical characteristics of thin films of Cu(In1–xGax)(SySe1–y)2 solid solutions with the chalcopyrite structure were investigated. The unit-cell constants according to x-ray diffraction analysis were a ~ 5.720 A and c ~ 11.52 A. The elemental compositions were x = Ga/(Ga + In) ~ 0.14 and y = S/(S + Se) ~ 0.11 for Cu(In1–xGax)(S ySe1–y)2 thin films. The optical band gap of Cu(In1–xGax)(S ySe1–y)2 solid solutions determined from measurements of photoluminescence spectra and luminescence excitation spectra at ~4.2 K was Eg ~ 1.122 eV. The mechanism of radiative recombination of nonequilibrium charge carriers in thin films of Cu(In1–xGax) (S ySe1–y)2 solid solutions is discussed.

From binary to multinary copper based nitrides – Unlocking the potential of new applications

• Diversity of synthetic strategies towards copper nitrides as bulk or thin films. • Overview of conditions that allow to control the morphology and particle size. • Structural diversity of multinary copper nitrides and their emerging applications. This review summarizes the current knowledge on the chemistry of binary copper(I) nitride, Cu 3 N and its multinary derivatives containing either main group or transition metal elements. For many years, research in this area was focused on the development of copper nitride prepared in the form of thin films. Successful deposition of these materials has been achieved mainly by employing physical methods, which have provided materials suitable for potential application in optical data storage. However, for the last decade, attention has also been devoted to expanding the available options by which Cu 3 N can be synthesized and deposited. Consequently, the focus has switched to the development of chemical synthetic methods towards the fabrication of this semiconductor and to broadening the range of related compounds that might be discovered. Simultaneously, the formulation of novel techniques and the successful preparation of new nanostructured functional materials has resulted in the rapid evolution of new and relevant applications; e.g. catalytic and electrochemical. The overview presented here concentrates on the chemical methods that have been devised to synthesise both bulk samples and thin films of Cu 3 N. Our article also shows how these approaches have been developed to achieve significant progress in the creation of multinary copper based nitrides and in identifying their potential applications. It provides a concise history of previous copper nitride research and sets the context for the most current advances. These will no doubt provide the springboard for future research areas that will impact both transition metal nitride chemistry and materials science more generally.

Излучательная рекомбинация на ионно-индуцированных дефектах в тонких пленках твердых растворов Cu(In, Ga)Se-=SUB=-2-=/SUB=-

In thin films of Cu(In,Ga)Se2 solid solutions radiation-induced effects after irradiation of hydrogen ions with an energy of 2.5, 5 and 10 keV with dose of ~ 3∙10^15 cm-2 were studied. A comparative analysis of the optical characteristics of non-implanted and implanted Cu(In,Ga)Se2 thin films was carried out based on the measurements of photoluminescence spectra and the luminescence excitation spectra at liquid helium temperature of ~ 4.2 K. The bandgap of Cu(In,Ga)Se2 solid solutions determined from the data of mathematical processing of the luminescence excitation spectra was ~ 1.171 eV. An intense band with a maximum of ~ 1.089 eV was found in the photoluminescence spectra of non-implanted and hydrogen-implanted Cu(In,Ga)Se2 thin films caused by the recombination of free electrons with holes localized in the tails of the valence band. It was established that appearance of intense broad bands in the photoluminescence spectra with maxima in the energy range of ~ 0.92 eV and ~ 0.77 eV is due to radiative recombination of nonequilibrium charge carriers at deep energy levels of acceptor type ion-induced defects formed in the bandgap of Cu(In,Ga)Se2 solid solutions. The conditions for the appearance of the ionic passivation effect of dangling electronic bonds on the surface and in the bulk of Cu(In,Ga)Se2 polycrystalline films, possible nature of point defects in the structure and the mechanisms of radiative recombination are discussed.

Spontaneous and Stimulated Emission in Thin Films of Cu(In1 –xGax)(SySe1 –y)2 Solid Solutions in the Сomposition of Solar Cells

The emission spectra of thin nanocrystalline films of Cu(In1 – xGax)(SySe1 – y)2 (CIGSSe) direct-gap solid solutions in the structure of solar cells, recorded upon continuous-wave laser excitation (~0.5 W/cm2) and nanosecond pulsed laser excitation with a power density in the range of 0.1–53 kW/cm2 at temperatures ranging from 10 to 300 K, are analyzed. It is found that stimulated emission (SE) occurs in thin CIGSSe films at temperatures from 10 to 90 K in the spectral range hν = 1.062–1.081 eV, with a minimum threshold-pump level of ~1 kW/cm2. It is shown that the spontaneous emission band is blue-shifted with an increase in the excitation intensity. It is also established that, with an increase in temperature, the photoluminescence (PL) band (upon weak excitation) and the stimulated-emission band are blue-shifted, whereas the PL band is red-shifted upon strong excitation. The possible reasons and mechanisms for the influence of temperature and excitation intensity on the spectral positions of the spontaneous and stimulated emission bands for the solid-solution films are discussed.

Young’s modulus and vibrational frequency dependence on shape and size in nanomaterials

In the present work, the dependence of thermodynamic properties on shape, size and dimension of the nanomaterials is studied. The theoretical model proposed by Lu et al. is used in the present work and the model is extended to calculate the variation in Young’s modulus and vibrational frequency with size of the nanomaterial for spherical, hexahedral and tetrahedral nanomaterials along with nanowires and thin films of metals Au, Ag and Cu. The present calculated results are found in good agreement with the available experimental data which proves the validity of the theoretical model used.