Cuprous Oxide Layer Research Articles

500 μm heavy micro-alloyed Cu wire for IGBT application: The study on microstructure characteristics, electrical fatigue fracture mechanism and bonding reliability

In this study, we introduced trace amounts of silver and nickel into 500 μm diameter copper wires to form micro-alloyed copper wires used in insulated gate bipolar transistors (IGBT). The addition of silver and nickel enhanced the mechanical properties of the conductors and suppressed the work hardening effect, significantly improving the power cyclic lifetime. Additionally, this study conducted chlorination and high-temperature oxidation test to compare the application characteristics of the heavy micro-alloyed copper wires with pure copper wires, through tensile and bending test, as well as electrical property comparisons. Finally, Cu50Ni (50 ppm Ni) wires were selected and nickel ceramic substrates for wire bonding to evaluate module electrical properties and bonding reliability.In the chloride test, there was no significant pitting corrosion observed in copper wire, and the micro-alloyed copper wire outperformed the pure copper wires in terms of bending lifetime and power cycling performance. In the high-temperature oxidation test, an oxide layer of cuprous oxide formed on the surface of all wires. The pure copper wire exhibited a significant increase in resistance. Notably, the micro-alloyed copper wires had better resistance to oxidation. Regarding wire bonding, the use of Cu50Ni wires and nickel ceramic substrates reduced the diffusion rate of nickel atoms from the substrate to the copper wire, forming a thinner alloy diffusion layer. This prevented electrical degradation and achieved high bonding reliability, especially under higher bonding forces. These findings confirm that micro-alloyed copper wires are suitable for high-power applications.

Room-temperature electrodeposition of Cu2O layers and its low-temperature annealing for photoelectrochemical water splitting applications

Cuprous oxide layers were obtained on a conductive glass substrate via room-temperature electrochemical deposition from the electrolyte containing 0.4 M CuSO4, 3 M lactic acid (pH = 12) at −0.5 V vs. SCE for various durations (from 0.25 to 3 h). Physicochemical properties of as-received FTO/Cu2O materials were characterized using SEM, PXRD, and UV–Vis DRS. The photoelectrochemical (PEC) properties of the obtained electrodes were evaluated in detail by analyzing the influence of the energy of monochromatic radiation, and the applied polarization on the resulting photocurrent transients. It was found that Cu2O crystals are getting bigger and sharper with prolonged electrosynthesis duration and a slight decrease in the band gap energy from 2.4 to 2.1 eV with increasing deposition duration was observed. Moreover, this trend was also reflected in PEC properties of resulted material, higher photocurrents were generated by the material deposited for 3 h. More importantly, this PEC response was enhanced by low-temperature (100 °C, 200 °C) annealing. Thermal treatment at 100 °C led to a noticeable improvement in the photoactivity of the samples. Further increasing post-treatment temperature to 200 °C resulted in a further six-fold increase in photocurrents. Finally, the calculated values of accumulated and dissipated charges indicated significantly lower surface recombination after thermal treatment.

Interfacial studies of Cu2O/TiO2 junction deposited at different electropotentials

Based on the simplistic two-step preparation method, a Cu2O/TiO2 junction was synthesized by electrodepositing a Cuprous Oxide layer on Titanium Oxide thin films at different deposition potentials. The thin films and junction were characterized for their structural, morphological, optical, and electrical properties using X-ray diffraction, Scanning Electron Microscopy, UV–visible spectroscopy, and Electrochemical Impedance Spectroscopy. The XRD analysis of the Cu2O/TiO2 junction indicated no sharp diffraction peaks of TiO2, only Cu2O peaks were observed. The Scanning Electron Microscopy also demonstrated that the Cuprous Oxide thin films possessed three-sided pyramidal structures on their surface. The band gaps of Cu2O and TiO2 thin films were calculated as 2.2 eV and 3.3 eV respectively by using Tauc’s plots. Electrochemical impedance spectroscopy revealed reduced interfacial charge transfer resistance and a boost in charge carrier generation in fabricated junctions (grown at −0.6 V). The flat band potentials and carrier concentrations of the fabricated thin films and their junction were calculated using Mott-Schottky analysis. Meanwhile, charge transfer resistance, solution resistance, constant phase element, and other circuit parameters of the electrochemical cell were studied using Nyquist plots.

Corrosion Evolution of Nickel Aluminum Bronze in Clean and Sulfide-Polluted Solutions

Nickel aluminum bronze (NAB) alloys are reported to suffer accelerated local corrosion in sulfide-polluted seawater. In this work, the real-time in situ scanning vibrating electrode technique (SVET) was employed to monitor the evolution of the corrosion product film of a typical NAB alloy immersed in the clean and sulfide-polluted 3.5% NaCl solutions. In the sulfide-free condition, the corrosion current peak surged at the individual point of the NAB surface and receded to calm in 2 h. In the presence of the sulfide, however, multiple active points on the measured metal surface released high corrosion current for a long time, indicating that intense corrosion had occurred. The corrosion mass loss was more than four times the former. Global electrochemical techniques, scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were adopted to perform a comprehensive analysis of the composition of the corrosion product films. The results show that a dense layer of aluminum and cuprous oxide forms on the NAB surface in the sulfide-free solution, while a loose mixture of cuprous sulfide and cuprous oxide is detected in the sulfide-contaminated solution. This finding is believed to account for the observed distinction between the corrosion behavior of NAB in the two solutions.

Investigation into Cu diffusion at the Cu/SiO2 hybrid bonding interface of 3D stacked integrated circuits

Reliability concerns are often risen for the hybrid bonding integration due to a potential misalignment in the bonding step leading that Cu directly faces dielectric at the hybrid bonding interface. Any Cu atomic or ionic diffusion could lead to serious decrease of the product lifetime. In the case of Cu/SiO2 interface, a self-formed cuprous oxide (Cu2O) layer that has some diffusion barrier characteristics was previously evidenced in the critical region where Cu is facing SiO2. In this paper, we investigate the immunity to both thermal (atomic) and field-enhanced Cu ion diffusion of the self-formed Cu2O barrier for the Cu/SiO2 hybrid bonding integration. The study of thermal diffusion by high precision analysis techniques shows limited Cu traces after bonding annealing. The same levels of Cu were also found in the presence of a SiN barrier. This study proves that the self-formed cuprous oxide and SiN have similar characteristics in decelerating Cu atomic diffusion. In addition, the study of the field-enhanced diffusion confirms that Cu2O is an effective barrier to Cu ionic drift even after long-term storage, which is chemically validated by a thermally stable interface. This self-formed Cu2O layer provides a negligible impact of Cu diffusion on the device performance.

Investigation on the electrochemical evolution of the Cu-sn-Pb ternary alloy covered with CuCl in a simulated atmospheric environment

• The long-term electrochemical evolution of Cu-sn-Pb alloy with CuCl patina is studied for the first time. • The impedance value increases at 0 ∼ 3 h, decreases at 3 ∼ 7 h, and recovers after 7 h during EIS monitoring. • The fluctuation of impedance value is related to the conversion of CuCl to Cu 2 O and the cycle of chloride ions. Nantokite (CuCl) layer induces severe corrosion of bronze by its active reactivity to copper alloy. To further understand its corrosion mechanism, this paper investigated the electrochemical evolution process of the Cu-S n-Pb ternary alloy covered with a CuCl layer by continuous electrochemical impedance spectroscopy (EIS) monitoring. And the EIS changing mechanism induced by dynamic Cl - circulation and the transformation of the CuCl were also discussed. The results showed that two extreme impedance value points, the 3rd and 7th hours, were observed during the evolution process of the CuCl layer within 48 h. The decrease of the impedance value at 0 ∼ 3 h was mainly affected by the reaction of CuCl hydrolysis forming a Cu 2 O film, while the increase of impedance value at 3 ∼ 7 h was affected by the reaction of copper attacked by chloride ion. After 7 h, the impedance value of the Cu-Sn-Pb alloys continued to increase due to the formation of a dense cuprous oxide layer and chloride ions migrating into solution.

Mg-doped Cu2O thin films with enhanced functional properties grown by magnetron sputtering under optimized pressure conditions

Cu2O appears as a promising material for synthesizing p-type transparent semiconducting oxides with low electrical resistivity and high optical transmittance. We report on an exhaustive study of magnesium-doped cuprous oxide layers deposited by radio frequency magnetron sputtering. We present the characterization of the structural and optoelectronic properties of Mg:Cu2O thin films deposited at room temperature with varied argon plasma pressure. As a result, we found that by adjusting the Ar plasma pressure, Mg-doped Cu2O layers with high crystallinity combined with optimal electrical and optical properties can be synthesized. Using a plasma pressure of 13 mTorr, we obtained a transparent p-type material with crystallite size of 15 nm, electrical resistivity of 10.2 Ωcm, and optical band gap of 2.55 eV.

Improving the Corrosion Resistance of Tin-bronze by Surface Modification

Bronze alloys are made of copper-based materials with another metal, usually tin. Many surface modification techniques such as chemical etching, oxidation, electro deposition and sol-gel could be employed to improve surface properties. The organic compound that was used in this study was extracted from chili peppers. FT-IR (Fourier-transform infrared) spectroscopy and UV (Ultraviolet) spectroscopy investigations were applied on the extracted compound and results showed that this compound is mainly capsaicin [N-(4-hydroxy-3-methoxybenzyl)-8-methylnon-trans-6-enamide) (HMMTE)]. Electrochemical deposition was employed under cell voltage equal to 30 volts in a two-electrodes cell where bronze was the anode and stainless steel was the cathode in a solution of 10 ml/L (HMMTE)/distilled-water. Modification of tin-bronze for 1 hr. in 10 ml/L HMMTE/ distilled water solution increased the contact angle from 48° to 132˚. Attension Biolin device (Model: Theta Optical Tensiometers) was used to measure the contact angle at ambient temperature. Electrochemical measurements revealed that a significant improvement in corrosion resistance of tin-bronze in 3.5% NaCl had been achieved. The corrosion rate of tin-bronze decreased from 10.22 mpy to 1.39 mpy. Surface morphology of the samples was investigated with scanning electron microscopy (SEN) and energy-dispersive X-ray (EDX). X-ray diffraction was employed to determined present phases. Surface investigations results confirmed that a layer of red cuprous oxide (Cu2O) was formed on the surface layer after modification which led to the improvement in corrosion resistance. Salt spray test was carried out using Alpha+ Salt Spray Testing Equipment for 13 days on the base and surface modified samples according to ASTM B117. A green layer from [CuCl2 and Cu46Cl24(OH)68-(H2O)4] was observed on the nonmodified specimen (could be patina and bronze disease) while the red layer [Cu2O] is still observed on the modified specimen. Adhesion test (using X-Cut Tape Adhesion test according to ASTM D3359) was also investigated.

On the growth of copper oxide nanowires by thermal oxidation near the threshold temperature at atmospheric pressure

This study focuses on the growth of copper oxide nanowires networks (CuO NWs) close to the onset temperature, found to be 310 ℃. The NWs were obtained by thermal oxidation in air of polycrystalline copper foils on hot plate. The investigated oxide layers with the NWs network on their surface grown between 200 ℃ and 440 ℃, were characterized by: SEM-EDX, STEM-EDX, XRD, and micro-Raman techniques. The accurate determination of copper content in self-exfoliated oxide sheets is above the stoichiometric concentration. XRD reveals nano-crystallites of 20–40 nm, in Cu2O phase of thick oxide sheets located close to the oxide-substrate interface. Statistical data on the average length of the NWs versus annealing time indicates unexpected early saturation in between 10 and 40 min at 320–340 ℃. A semi-empirical model proofs quantitatively that the emerging delays of the NWs relative to the start of copper oxidation determine the plateau of the average length versus time. The excess concentration of copper found in the cuprous oxide layer is cautioned to accompany the early saturation effect having critical restrictions regarding the oxidation time and temperature. This study sustains the development of control and monitoring methods, applied to the growth of CuO NWs.

From Electrical to Physical-Chemical Characterization of the Cu/SiO₂ Hybrid-Bonding Interface—A Cu₂O-Layer as a Cu Diffusion Barrier?

This letter discusses copper (Cu) diffusion in the framework of the development of future 3D stacked devices by means of hybrid bonding-based interconnects. Indeed, at the bonding interface, due to the bonding tool accuracy, an inherent misalignment exists between top and bottom tiers leading to a direct contact between copper and neighboring dielectrics. Our experimental studies do not evidence any copper diffusion for the analyzed hybrid bonding-based test structures. Indeed, BTS/TVS (Bias Temperature Stress/Triangular Voltage Sweep) electrical characterization does not evidence any mobile ions diffusion. Our Electron Energy Loss Spectroscopy (EELS) analysis reveals the presence of a thin layer (~3 nm) of cuprous oxide (Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O) at the copper/dielectric interface that most probably acts as a diffusion barrier to copper.

Enhancement of efficiency and external quantum efficiency of CIGSSe solar cell by replacement and inserting buffer and Cu2O ER-HTL layer

In this article, the performance of CIGSSe solar cells have been analyzed in two stages. Firstly, a conventional structure MgF2/ZnO:B/CdS/CIGSSe/Mo has been simulated based on experimental data to validate the results. Three toxic-free, buffer layer materials ZnSnO, ZnS and ZnMnO have been used in the conventional structure. Secondly, the recombination loss has been reduced and external quantum efficiency (EQE) has been increased by adding p-type cuprous oxide (p-Cu2O) layer at back surface field (BSF) contact. BSF acts as an electron reflected-hole transport layer (ER-HTL) in a conventional structure and proposed CIGSSe solar cell. The efficiency and EQE of the proposed Type-II solar cells have been increased by 5.94% and 2% respectively by optimizing cell parameters in terms of thickness, energy bandgap and doping concentration. It is shown that the proposed solar cell with ZnMnO as buffer layer achieves a conversion efficiency of 28.86%.

Effects of Mg% on open circuit voltage and short circuit current density of Zn1-xMgxO/Cu2O heterojunction thin film solar cells, processed using electrochemical deposition and spin coating

Zn1-xMgxO/Cu2O/Ag solar cells were fabricated upon fluorine doped tin oxide coated soda lime glass substrate with varying percentage of Mg mol% doping in zinc oxide (ZnO) layer. Short circuit current density & open circuit voltages of the fabricated cells were investigated. Optimum doping with Mg improved the transparency of ZnO layer which helped in increasing the short circuit current density of solar cells. An enhancement of open circuit voltage was observed with increase in x, which was investigated using X-ray photoelectron spectroscopy and the results revealed that with increase in x, there was a decrease in conduction band offset between Zn1-xMgxO and cuprous oxide layers. From UV-Visible transmittance spectra, it was observed that with Mg doping in ZnO nanostructure, optical losses were reduced which resulted in increase in Short circuit current density. The objective of this study was to investigate and develop a technology for fabrication of solar cells that is both cost effective and easy to produce.

Numerical modelling and optimization of CdS/CdTe solar cell with incorporation of Cu2O HT-EBL layer

In the recent years, use of CdTe thin-film as an absorber in solar cells has been augmented significantly due to high device efficiency, stability in the performance and cost effectiveness. In this work, CdTe solar cell has been investigated employing 2-dimensional numerical simulations using TCAD Silvaco-Atlas simulator. Initially, a reference structure of FTO/i-SnO2/CdS/CdTe solar cell was simulated based on experimental data for the validity of the simulation and the extent to which present results agree to the experimental data. To reduce the minority carrier recombination loss, a new structure is proposed by incorporation of the cuprous oxide (p-type Cu2O) layer at back-contact as a hole transport-electron blocking layer (HT-EBL). High performancehas been obtained by optimizing the cell parameters in terms of thickness, doping concentration and carrier lifetime. The efficiency of the structure is increased by 10.35% compared to the recent experimental results. Furthermore, the proposed structure consists of FTO/i-SnO2/CdS/CdTe/Cu2O presents the best conversion efficiency of 24.35%, short-circuit current density of 27.59 mA/cm2, open-circuit voltage of 1.03 V and fill-factor of 85.83%, under the air mass 1.5 global spectrum (AM1.5G).

Early-stage corrosion, ion release, and the antibacterial effect of copper and cuprous oxide in physiological buffers: Phosphate-buffered saline vs Na-4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid

Copper surfaces are well known for their antibacterial effects due to the release of copper ions. This benefit has been shown in many antibacterial efficiency tests, however, without considering the corrosion behaviors of copper in the physiological solutions, which could play an indispensable role in ion release from the metallic surface. This study compared the ground copper surface and sputtered cuprous oxide (Cu2O) coating in two common physiological buffers: phosphate-buffered saline (PBS) and Na-4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (Na-HEPES). The growth of the cuprous oxide (Cu2O) layer was found on copper in pure PBS, inhibiting further copper ion release. In contrast, a continuous release of copper ions was recorded in Na-HEPES for 3 h, where no oxide formation was observed. The antibacterial efficiency of copper (against E. coli) was measured and discussed with the ion release kinetics in the presence of E. coli. Similar results were obtained from Cu2O coating, ruling out its assisting role in showing the antibacterial property from copper surfaces, but they did indicate the importance of taking environmental parameters into consideration in interpreting the antibacterial efficiency of copper surfaces.

Bacteria accumulate copper ions and inhibit oxide formation on copper surface during antibacterial efficiency test

Copper surface after antibacterial test against E. coli was examined in the aspect of corrosion. Results from scanning electron microscope (SEM), grazing incidence X-ray diffractometer (GIXRD) and Raman spectroscopy together confirmed less oxidation on copper surface with the presence of E. coli. The inhibition of the cuprous oxide (Cu2O) layer instead ensured the continuous exposure of copper surface, letting localised corrosion attacks observable and causing a stronger release of copper ions. These phenomena are attributed to the fact that E. coli act as ions reservoirs since high amount of copper accumulation were found by energy dispersive X-ray spectroscopy (EDS).

Potentiostat Electro-Deposited Cuprous Oxide and Cupric Oxide Thin Films for Photovoltaic Use

To withstand the rising demand for energy while fuel and chemical energy are becoming rare, the development in the production of solar energy has become a necessity. There is a variety of solar cells; among them, thin-film photovoltaics is more popular because of low-cost production and good-efficiency. Nowadays, copper oxide has become popular to make thin film layers like CZTS, CIGS, etc. Unfortunately, the efficiency of these thin films is less than 20%. In order to obtain better efficacy, an investigation of the layers of thin films is needed. This research discussed the properties of copper and its oxides. In case of making the thin film layers, potentiostat electro-deposition was the chosen method where bath composition of CuSO4.5H2O solution, temperature, time, potential difference were the variable parameters. The best-deposited layers were obtained in 0.2 M concentration, 40 minutes, -0.5 V potential difference and 65oC. Hence, physical properties like thickness and hardness, and characterisation properties like X-ray diffractometry (XRD), scanning electron microscopy (SEM), UV-Vis spectrometry are observed to compare cupric oxide (CuO) and cuprous oxide (Cu2O) thin films. CuO thin film shows better stability and rigidity than the Cu2O thin film. But the thin film layer of cuprous oxide illustrates good homogeneity and nodular form. From the test mentioned above data, band gap has been measured for each deposited film, and the CuO thin film layer is raked out having a better band energy gap than the Cu2O thin film layer.

A neutron scattering and electron microscopy study of the structure, wetting, and freezing behavior of water near hydrophilic CuO-nanostructured surfaces

Oscillating heat pipes (OHPs) provide a promising heat transfer device for a variety of applications, including the cooling of electronic devices. Recently, it has been shown that a hydrophilic, nanostructured cupric oxide (CuO) coating can significantly enhance the thermal performance of copper OHPs that use water as the working fluid. Motivated by these results, we report neutron scattering and electron microscopy (EM) measurements to investigate the interaction of water with copper-oxide surfaces on the nanoscale. Our measurements confirm earlier observations of a thin cuprous oxide (Cu2O) layer growing on a bare copper substrate followed by “grass-like” CuO nanostructures. New evidence of the nanostructure hydrophilicity is provided by EM measurements of wetting and by our high-energy-resolution elastic neutron scattering measurements, showing a continuous freezing and melting of the water in our samples over a temperature range of ∼80 K. In addition, our neutron diffraction measurements are consistent with water closest to the CuO nanostructures freezing into an amorphous solid at low levels of hydration and hexagonal ice at higher hydration. In short, our findings support a strong interaction of water with the CuO nanostructures, which could significantly affect the operation of an OHP.

N-Type Cu2O/α-Fe2O3 Heterojunctions by Electrochemical Deposition: Tuning of Cu2O Thickness for Maximum Photoelectrochemical Performance

Abstract Here, we report the enhanced photoelectrochemical performance of surface modified hematite thin films with n-type copper oxide nanostructures (Cu2O/Fe2O3) obtained through simple electrochemical deposition method. The thickness and amount of cuprous oxide layer were varied by simply changing the number of electrodeposition cycles (viz. 5, 10, 25, 50 and 100) in order to understand its thermodynamic and kinetic influence on the photoelectrochemical activity of the resultant nano-heterostructures. Structural and morphological characteristics of the obtained Cu2O/Fe2O3 films have been studied by absorption spectroscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy analysis. Electrochemical investigations such as linear sweep voltammetry, Mott–Schottky analysis, and electrochemical impedance spectroscopy suggested the formation of n-type Cu2O layers over the hematite films with varying charge-carrier densities, ranging from 0.56×1019 to 3.94×1019 cm−3, that varies with the number of cycles of electrochemical deposition. Besides, the thickness of deposited cuprous oxide layer is noted to alter the net electrochemical and photo-electrochemical response of the base material. An interesting, peak event was recorded for a particular thickness of the cuprous oxide layer (obtained after 25 cycles of electrochemical deposition) below and above which the efficiency of catalyst was impaired. The heterojunction obtained thus, followed well known Z-scheme and gave appreciable increment in the photocurrent response.

A Cuprous Oxide Thin Film Non-Enzymatic Glucose Sensor Using Differential Pulse Voltammetry and Other Voltammetry Methods and a Comparison to Different Thin Film Electrodes on the Detection of Glucose in an Alkaline Solution.

A cuprous oxide (Cu2O) thin layer served as the base for a non-enzymatic glucose sensor in an alkaline medium, 0.1 NaOH solution, with a linear range of 50–200 mg/dL using differential pulse voltammetry (DPV) measurement. An X-ray photoelectron spectroscopy (XPS) study confirmed the formation of the cuprous oxide layer on the thin gold film sensor prototype. Quantitative detection of glucose in both phosphate-buffered saline (PBS) and undiluted human serum was carried out. Neither ascorbic acid nor uric acid, even at a relatively high concentration level (100 mg/dL in serum), interfered with the glucose detection, demonstrating the excellent selectivity of this non-enzymatic cuprous oxide thin layer-based glucose sensor. Chronoamperometry and single potential amperometric voltammetry were used to verify the measurements obtained by DPV, and the positive results validated that the detection of glucose in a 0.1 M NaOH alkaline medium by DPV measurement was effective. Nickel, platinum, and copper are commonly used metals for non-enzymatic glucose detection. The performance of these metal-based sensors for glucose detection using DPV were also evaluated. The cuprous oxide (Cu2O) thin layer-based sensor showed the best sensitivity for glucose detection among the sensors evaluated.

Pure and Oxidized Copper Materials as Potential Antimicrobial Surfaces for Spaceflight Activities.

Microbial biofilms can lead to persistent infections and degrade a variety of materials, and they are notorious for their persistence and resistance to eradication. During long-duration space missions, microbial biofilms present a danger to crew health and spacecraft integrity. The use of antimicrobial surfaces provides an alternative strategy for inhibiting microbial growth and biofilm formation to conventional cleaning procedures and the use of disinfectants. Antimicrobial surfaces contain organic or inorganic compounds, such as antimicrobial peptides or copper and silver, that inhibit microbial growth. The efficacy of wetted oxidized copper layers and pure copper surfaces as antimicrobial agents was tested by applying cultures of Escherichia coli and Staphylococcus cohnii to these metallic surfaces. Stainless steel surfaces were used as non-inhibitory control surfaces. The production of reactive oxygen species and membrane damage increased rapidly within 1 h of exposure on pure copper surfaces, but the effect on cell survival was negligible even after 2 h of exposure. However, longer exposure times of up to 4 h led to a rapid decrease in cell survival, whereby the survival of cells was additionally dependent on the exposed cell density. Finally, the release of metal ions was determined to identify a possible correlation between copper ions in suspension and cell survival. These measurements indicated a steady increase of free copper ions, which were released indirectly by cells presumably through excreted complexing agents. These data indicate that the application of antimicrobial surfaces in spaceflight facilities could improve crew health and mitigate material damage caused by microbial contamination and biofilm formation. Furthermore, the results of this study indicate that cuprous oxide layers were superior to pure copper surfaces related to the antimicrobial effect and that cell density is a significant factor that influences the time dependence of antimicrobial activity. Key Words: Contact killing-E. coli-S. cohnii-Antimicrobial copper surfaces-Copper oxide layers-Human health-Planetary protection. Astrobiology 17, 1183-1191.