Single Bath Research Articles

A Breakthrough in Pb-Free Solder Electroplating

The progression in the electronics industry is toward further minimization and the global semiconductor assembly community is striving for a robust replacement for leaded solders due to increased environmental regulations. A family of Pb-free solder alloys based on Sn-Ag-Cu (SAC) compositions has shown promise, but due to reliability issues in certain assembly and operating environments, quaternary (Mn, Ni, Zn, and Al-doped SAC) solders are currently under investigation. With more computing power, higher performance is needed for smaller areas. The ball-grid-array (BGA) packaging system with a decreased size, is likely to be replaced by chip-scale packages (CSPs) (i.e. µBGA) and Copper Pillar Bumps (CPBs). There are several methods to form solder bumps such as screen printing, evaporation and electroplating. As the pitch and the bump size decrease, electroplating becomes the only efficient way to fabricate bumps with small size, fine pitch and low cost. Electroplating is considered to be the only feasible technique to form the copper pillar and the solder cap to realize the CPBs. Currently, solder electroplating is limited mainly to binary compound plating and there exist no stable solutions for electroplating of ternary alloys due to a large gap in electrochemical reduction potentials between different elements. For example, in order to perform SAC electroplating Karim et al. had to use sequential plating from two separate binary SnCu and SnAg plating solutions [1]. However, if developed, ternary alloy plating solutions may not be practical under manufacturing conditions considering that it is hard to maintain bath and alloy composition even for binary plating solutions. Obviously the development of a plating solution for quaternary alloy is even less probable. In order to deposit alloy with precise composition, multilayer electroplating method is proposed instead. The method lies in the sequential electroplating of each of the solder components from a separate bath and a consequent reflow to form uniform alloy. Unfortunately to warrantee the reliability the electroplating sequence should be carefully watched [2]. To overcome inter-diffusion limitation and achieve a uniform and fast reflow, low thickness of each layer is necessary and a proportional increase of layers number makes the process time-consuming and impractical from a conventional electroplating point of view due to multiple switching between solution baths. The present work will show how using a new concept in electroplating, based on multiple Dynamic Liquid Drop/Meniscus (DLD/DLM), is possible to realize multilayer approach to plate binary, ternary and even quaternary solder alloy at high throughput, high precision and low cost. The DLD/DLM [3] represents a constantly refreshed confined electrolyte volume in touch with a substrate surface. The plating concept lies in assembling multiple independent DLD/DLM in a sequential array (one or many for each plating component intercalated by a rinse DLD/DLM) into a multiple plating head. Thus scanning the plating head over the wafer surface will allow consequent plating of a layer of each of the component. Each pass of the plating head leads to deposition of the multilayered structure representing consequent components layers (grains) with a required proportion. Total thickness of the alloy depends on the number of passages and can be varied in a wide range. Using the proposed technique various solder compositions were deposited. As a proof-of-concept, SAC305 and SAC405 layers with 30µm thickness were deposited containing more than 350 layers of each element. A detailed investigation of SAC and quaternary SAC+Mn alloys composition will be presented; EDX analysis before and after reflow proving that the high number of layers an homogenous solder is obtained independently of metal deposition sequence and even without reflow. The proposed breakthrough technique offers the unique opportunity to deposit any kind of binary, ternary and quaternary Pb-free alloy solder from single bath solutions without any kind of cross contamination. Such technique poses a key milestone to obtain ternary and/or quaternary Pb-free solder alloy for the CSPs and CPBs allowing to tune the correct solder alloy in order to finally solve reliability issues. [1] Z. S. Karim and J. Martin, “Lead-free solder bump technologies for flip-chip packaging applications”, SMTA (2001). [2] Qinghua Zhao, Anmin Hu, Ming Li, Jiangyan Sun, “Effect of electroplating layer structure on shear property and microstructure of multilayer electroplated Sn-3.5Ag solder bumps” Microelectronics Reliability 53 (2013) 321–326 [3] Konstantin Kholostov, et al. “High uniformity and high speed copper pillar plating technique” IEEE 64th Electronic Components and Technology Conference (ECTC), 2014, 1571-1576 Figure 1 shows the SEM pictures and EDX analysis of SAC 305 μBGA by multiple DLD/DLM technique. Figure 1

Simultaneous dyeing and anti-bacterial finishing on 100% cotton fabric: process establishment and characterization

Nowadays, there is less emphasis on the aesthetic traits of textiles and more on their functionality. Traditionally functional textiles are prepared in two steps including dyeing and then finishing. This adds extra cost to the process through more energy consumption and water effluent. Current research deals with a single bath application of antibacterial finish with reactive dyeing. L-cysteine (L-cys) is a natural defensive thiolated amino acid found in many living organisms and is applied to cotton fabric through simple conventional reactive dyeing method. Fabrics with L-cys were assessed against both Escherichia Coli and Staphylococcus Aureus strains and promising results were found containing antibacterial activity up to 20 washes. The fastness properties of antimicrobial dyed fabrics were unaffected when compared with control samples. However, shade depth (k/s) was decreased with increasing amount of antibacterial agent while control samples showed highest value. This proposed process reduces chemical- and energy consumption, as well as water effluent.

The Role of Cu Length on the Magnetic Behaviour of Fe/Cu Multi-Segmented Nanowires.

A set of multi-segmented Fe/Cu nanowires were synthesized by a two-step anodization process of aluminum substrates and a pulsed electrodeposition technique using a single bath. While both Fe segment length and diameter were kept constant to (30 ± 7) and (45 ± 5) nm, respectively, Cu length was varied between (15 ± 5) and (120 ± 10) nm. The influence of the non-magnetic layer thickness variation on the nanowire magnetic properties was investigated through first-order reversal curve (FORC) measurements and micromagnetic simulations. Our analysis confirmed that, in the multi-segmented Fe/Cu nanowires with shorter Cu segments, the dipolar coupling between Fe segments controls the nanowire magnetic behavior, and its performance is like that of a homogenous Fe nanowire array of similar dimensions. On the other hand, multi-segmented Fe/Cu nanowires with larger Cu segments act like a collection of non-interacting magnetic entities (along the nanowire axis), and their global behavior is mainly controlled by the neighbor-to-neighbor nanodisc dipolar interactions.

Habitual hot water bathing protects cardiovascular function in middle-aged to elderly Japanese subjects

Favorable effects of sauna bathing on cardiovascular disease have been demonstrated. Hot water bathing is an alternative, and could also have similar effects. Information pertaining to hot water bathing frequency and water temperature was obtained from 873 subjects. Carotid mean and max intima-media thickness (IMT) and brachial-ankle pulse wave velocity (baPWV) were measured as indices of atherosclerosis. Central haemodynamics were evaluated using radial pulse waveform analyses. Plasma levels of B-type natriuretic peptide (BNP) were measured as an index for cardiac loading. The mean duration of a single hot bath was 12.4 ± 9.9 min. Subject bathing in hot water ≥5 times per week had significantly lower baPWV, central pulse pressure (PP), and BNP after correcting for possible confounding parameters. Stepwise regression analyses revealed that hot water temperature was negatively associated with baPWV, while bathing frequency was negatively related to central PP and BNP. A longitudinal follow-up in 164 subjects showed that hot water bathing ≥5 times per week was associated with significantly lower increase in BNP over time, while the temperature of the water tended to be related to lower increases in carotid max IMT and baPWV. Hot water bathing showed a favorable effect on atherosclerotic and central haemodynamic parameters.

Improvement of SO2 adsorption capacity of fiber web surface produced from continous graphene oxide fiber

Sulphur dioxide (SO2) is an important atmospheric pollutant, and capture of SO2 is of great importance for the environment, human health and market. Carbon based materials, especially activated carbon, are mostly used for adsorption purposes. However, there is a notable lack on adsorption of SO2 on graphene oxide (GO) fibers and fiber web surface. In this study, the effect of addition of activated carbon, pH of GO dispersions, hydrazine reduction and oxygen/argon plasma treatment on SO2 adsorption of GO fiber web surface were evaluated. It was seen that GO fiber web surface with activated carbon provides high SO2 adsorption (896 mg SO2/g) which is very higher than many of carbon based materials presented in the literatures. Single coagulation bath increases surface roughness of fiber and provides higher functional group than three coagulation baths leading to higher SO2 adsorption capacity.

Partial entropy production in heat transport

We consider a system of two Brownian particles (say A and B), coupled to each other via harmonic potential of stiffness constant k. Particle-A is connected to two heat baths of constant temperatures T1 and T2, and particle-B is connected to a single heat bath of a constant temperature T3. In the steady state, the total entropy production for both particles obeys the fluctuation theorem. We compute the total entropy production due to particle-A in the coupled system (partial and apparent entropy production) in the steady state for a time segment τ. When both particles are weakly interacting with each other, the fluctuation theorem for partial and apparent entropy production is studied. We find a significant deviation from the fluctuation theorem. The analytical results are also verified using numerical simulations. Furthermore, we investigate the effect of hidden fast degrees of freedom on the steady state fluctuation theorem for a system of a single Brownian particle coupled to two heat baths of distinct temperatures and dissipation constants, and coupled to a third heat bath of vanishing temperature and dissipation constant.

Crystal Quality and Photoelectrochemical Response of Bismuth Containing Cu2ZnSnS4 (CZTS) Absorber Layers for Photovoltaic Applications

Kesterite, Cu2ZnSnS4 (CZTS), absorber layer based solar cells are unique owing to their earth-abundant, non-toxic elements; however, the record efficiency, ~12 %, is still lower than the calculated theoretical values [1,2]. The crystallographic properties of CZTS absorber layers, which are found to influence the solar cell efficiency, can be manipulated with a suitable element [3, 4]. Bismuth has been shown to work as a fluxing element and enhance the grain growth of CZTS crystals [5,6], however it has been studied only to a limited extent and further studies are required to investigate the influence of bismuth on the properties of CZTS thin films. In this study, first we electrodeposited suitable Cu-Zn-Sn-Bi (CZTB) metallic precursors from a single deposition bath and synthesized CZTS layers with bismuth (CZTS-Bi) via sulfurization. Second, we investigated the crystallographic features of the resulting CZTS-Bi layers to inspect the doping role of Bi. Composition was determined by EDS and structural properties were analyzed with XRD and Raman Spectroscopy. Lastly, we presented the correlation between photoelectrochemical (PEC) performance and crystallographic properties of CZTS only and CZTS-Bi layers. The incorporation of Bi into the CZTS lattice is found to be limited to ~0.5 at% Bi, and above this amount we observed Bi-rich secondary phases in the layers. We found that Bi additions do increase the grain size, suggesting that it is acting as a fluxing agent; in addition, the FWHM analyses of films with XRD and Raman spectra are in agreement with regard to the better crystallinity of CZTS-Bi films vs. CZTS only layers. Figure 1 shows the PEC response of the CZTS only and CZTS-Bi thin films a function of Zn/Sn ratio. The PEC response of the layers increased with the increasing Zn/Sn ratio for both of the CZTS only and CZTS only layers. The photoresponse of the CZTS-Bi layers is higher than the CZTS layers for Zn/Sn ratio above 0.90. CZTS-Bi layer also showed the highest PEC response in these set of samples, with a 2.65 mA/cm2 photoresponse at -0.95 V. The improvement of the PEC performance is attributed to two reasons; the increase of the grain size and the improvement of the chemical order of the CZTS lattice, which influences the electronic structure, hence band gap, of the CZTS material.

CuNi Alloy Electrodeposition for Microbumps Using Benzotriazole

A pressing issue in flip-chip and stacked integrated circuit (SIC) technology is the breakdown of microbumps over time. These microbumps are the physical and electrical connections between the chips. They consist out of Cu stages on both chips which are typically soldered together by Sn. Due to diffusion and electromigration, Cu and Sn form two intermetallic phases of which Cu3Sn induces microvoids at the Cu3Sn/Cu interface causing in turn breakdown of the microbump. Chemical modelling shows that a CuNi alloy, with an approximate 9:1 Cu:Ni ratio, together with Sn doesn’t form the Cu3Sn intermetallic compound thus tremendously improving the stability of the microbumps, and therefore the chip. By far the most feasible method to manufacture microbumps is galvanostatic electrochemical deposition. However, electrochemical CuNi co-deposition from a single deposition bath requires current densities higher than the limiting current density of copper causing rough, uncontrolled dendritical growth of Cu. Existing CuNi baths are citrate based but citrates can corrupt other features of the chip manufacturing process. In this work the possibility of smooth, solid solution electrodeposition of CuNi in a 9:1 ratio using benzotriazole (BTA) is investigated. Benzotriazole is a well-known corrosion inhibitor for copper. Here we show that BTA has a tremendous potential for suppressing Cu2+ reduction and limiting the uncontrolled mass-transfer limited Cu growth. First we demonstrate with a RDE voltammetric investigation, together with viscosimetry, the effects of the combination of an existing CuSO4 and a NiSO4 bath on Cu2+ reduction. Then, we introduce BTA and show the large difference between the working of BTA in the combined bath and in a CuSO4 only bath. Later, we improve the working of BTA by increasing the pH thus defining a parameter window for which we’re able to deposit CuNi with a maximum suppressing effect of BTA. CuNi deposits on metal pellets with a Cu substrate layer are investigated by SEM and EDX to evaluate the morphology and elemental composition of the deposit. We were able to demonstrate the change in CuNi morphology upon increasing the BTA concentration from 0 to 1000 ppm. No distinction could be made in Cu or Ni rich areas over different deposit areas indicating that we’re able to deposit CuNi as a solid solution. Figure 1

Efficacy and Safety of Topical Fipronil 1% and Deltamethrin 0.1% in Water Buffaloes (Bubalus bubalis) Naturally Infested by Haematopinus tuberculatus

Haematopinus tuberculatus is the main arthropod affecting buffaloes around the world. It causes intense itching and restlessness, altering feeding habits, thus reducing animal productivity. This parasitosis is seldom studied, as it does not lead to significant animal mortality or financial losses. In this project, we evaluated the efficacy and safety of two commercially available products for control of pediculosis in naturally infested buffaloes. A total of 24 milk producing, clinically healthy female buffaloes that were naturally infested by lice were included in this study. Animals were equally distributed into two groups: group 1 was treated with a single dose of pour on Fipronil (1%, Carval de Colombia, 1 ml of product per 10 kg of live weight). Group 2 was treated with a single dose of deltamethrin (5%, Bioara, SA), at a final concentration of 0,1% applied with an aspersion pump as a single bath of 4 liters of diluted solution per animal. Lice were counted weekly from day 1 to day 58 post-treatment. Up to day 23 post-treatment, no significant differences in efficacy were observed between products.Fipronil 1% consistently exhibited an efficacy above 70% from day 8 and until 30 day of the study. These results suggest that both products are efficient and safe to control lice infestations in buffaloes. However, fipronil 1% exhibited a greater residual effect, which reduces the number of baths required to treat infested animals, and reduces the probability of selecting for drug-resistant lice populations

Optimization of Wool and Silk Blend Dyeing Using α-Bromoacrylamido Reactive Dyes by Response Surface Methodology

Dyeing of wool and silk fibre blend in a single bath dyeing process is very difficult process due different absorption of dyestuff by these fibres. Wool is become darker than the silk fibre. Here wool fibre is first pretreated with a commercial syntan and then dyed with silk fibre using I± bromoacrylamido reactive dyes. The process of dyeing is optimized my Central composite design using response surface methodology.

Ni-P/Zn-Ni compositionally modulated multilayer coatings – Part 1: Electrodeposition and growth mechanism, composition, morphology, roughness and structure

The Ni-P/Zn-Ni compositionally modulated multilayer coatings CMMCs were electrodeposited from a single bath by switching the cathodic current density. The composition, surface morphology, roughness, layers growth pattern as well as the phase structure of deposits were extensively studied via SEM, EDS, AFM and XRD analysis. Effects of bath ingredients on the electrodeposition behavior were analyzed through cathodic linear sweep voltammetry. Although the concentration of Zn2+ in bath was 13 times higher than Ni2+, the Zn-Ni deposition potential was much nearer to Ni deposition potential rather than that of Zn. Addition of NaH2PO2 to the Ni deposition bath considerably raised the current density and shifted the crystallization potential of Ni to more nobble values. Codeposition of P with Zn-Ni alloy lead to crack formation in the monolayer that was deposited in 60 mA/cm2. However, the cracks were not observed in the Zn-Ni layers of multilayers. Zn-Ni layers in CMMCs exhibited a three-dimensional pattern of growth while that of Ni-P layers was two-dimensional. Also, the Ni-P deposits tends to fill the discontinuities in Zn-Ni layers and performed leveling properties and lowered the surface roughness of Zn-Ni layers and CMMCs. Structural analysis demonstrated that Ni-P layers were amorphous and the Zn-Ni layers exhibited crystallite phase of Zn11Ni2. Thus, the Ni-P/Zn-Ni CMMCs comprised of alternate layers of amorphous Ni-P and nanocrystalline Zn Ni.

Ni-P/Zn-Ni compositionally modulated multilayer coatings – Part 2: Corrosion and protection mechanisms

The Ni-P/Zn-Ni compositionally modulated multilayer coatings CMMCs were electrodeposited from a single bath by switching the deposition current density. The corrosion resistance of the deposits was studied and compared with that of monolayers of Ni-P and Zn-Ni alloys via Tafel polarization, EIS and salt spray tests. Characterization of corrosion products by means of EDS and XRD revealed more details from the corrosion mechanism of the monolayers and multilayers. The corrosion current density of Ni-P/Zn-Ni CMMCs were around one tenth of Zn-Ni monolayer. The CMMC with incomplete layers performed lower polarization resistance and higher corrosion current density compared to the CMMC with complete layers. The electrical circuit that was proposed for modeling the corrosion process based on the EIS spectrum, proved that layering reduces the porosity and consequently improves the barrier properties. Although, layering of Zn-Ni layers with Ni-P deposits increased the time to red rust in salt spray test, the time for white rust formation decreased. The corrosion mechanism of both Zn-Ni and Ni-P (containing small amount of Zn) was preferential dissolution of Zn and the corrosion products were comprised of mainly Zn hydroxychloride and Zn hydroxycarbonate. Also, Ni and P did not take part in the corrosion products. Based on the electrochemical character of the layers and the morphology of the corroded surface, the corrosion mechanism of multilayers was discussed.

Electrochemical Deposition of CoCu/Cu Multilayers: Structural and Magnetic Properties as a Function of Non-magnetic Layer Thickness

Abstract Electrochemical deposition of CoCu/Cu multilayers was performed on titanium substrates from a single bath as a function of the Cu layer thicknesses. The deposition potentials were selected as −1.5 V for the magnetic layers and −0.3 V for the non-magnetic layers with respect to the saturated calomel electrode. The current-time transients were obtained during the deposition process, and the Co layer deposition and capacitive transients were calculated. On the basis of structural analysis, the multilayers were found to be polycrystalline with both Co and Cu layers adopting the face-centered cubic structure. The calculated lattice parameters of the multilayers slightly increase from 0.3585 to 0.3615 nm with increase in the Cu layer thickness, which is consistent with the bulk value of Cu. The inter-planar distance of the peaks of the multilayers is closer to that of Cu (d 111=0.2087 nm) and Co (d 111=0.2046 nm), and they become close to that of bulk Cu with increasing Cu layer thickness. In magnetic measurements, the magnetization decreases from 156 to 44 emu/cm3 depending on the Cu layer thickness. Furthermore, the coercivity of the multilayers increases from 20 to 140 Oe. These values show that the magnetic behaviour of the multilayers lie between those of soft and hard magnetic materials, but the multilayer having 2.5 nm Cu layer thickness shows hard magnetic property. For the CoCu(4 nm)/Cu(0.7 nm) multilayer, the magnetoresistance measurement shows 5.5 % giant magnetoresistance (GMR).

Study on the Comparison of the Effects of pH Buffer in Single Stage Preparatory Process with that of Conventional for CVC Woven Fabric

To minimize water and energy consumption, it has become necessary to combine several textile processing stages in order to reduce the number of operations, process time and cost. In this project work an attempt was made to combine the pre-treatment process with optimal quantities of chemicals in single bath by varying different pH with the help of different buffers and comparison was made with conventional process. It has found that buffered system at pH 11 for 60 min shows the best result in respect to wicking test, drop test, immersion test, weight loss%, whiteness index, yellowness index. Then all the pre-treated samples were dyed with reactive dyes by varying the depth of shade. After dyeing it has been found that buffered system at pH 11 for 60 min can be selected for any depth of shades and buffered system at pH 11 for 45 min is suitable for dark shade. This kind of a one-bath process is shorter, consuming less energy and hence being less expensive. The combined processes also lead to substantial saving in water energy and time along with chemicals.

Electrodeposition of a Functional Solid State Memory Material: Germanium Antimony Telluride from a Non-Aqueous Plating Bath

The electrodeposition of germanium antimony telluride (GST) alloys from a single non-aqueous plating bath based on tetrabutylammonium chlorometallate precursors is presented. The system provides a case-study for plating bath optimization in order to produce complex functional materials. GST deposits in the amorphous phase and the film composition and morphology can be readily adjusted by tuning the three precursor concentrations and the electrodeposition potential. Adjustment of the precursor concentrations allows the preparation of deposits ranging from the binaries (GeSb, GeTe, Sb2Te3) to ternaries with a wide range of compositions, including the standard Ge2Sb2Te5 composition – more commonly known as GST-225 – which is widely used in the solid state memory industry. In this paper we present a detailed study discussing the complex interplay between the deposition of germanium, antimony and tellurium and how adjusting the concentrations of their chlorometallates allows control over the composition and also the morphology of the deposits. We also highlight the benefits that arise from the wide separation in the deposition potentials for the three precursors, and in particular the ability to control the composition through modulation of the deposition potential.

Comparative Study Between Mixed Dyeing of Wool Fiber in One and Two Dye Baths with Natural Indigo and Madder Colorants

The objective of the present study was to compare between the mixed dyeing of wool fiber in one and two dye baths using natural indigo (<i>Indigofera tinctoria</i>) and madder colorants (<i>Rubia tinctorum</i>). Based on the reduction and oxidation reaction conditions under the same dyeing mechanism for the indigo and madder colorants, the exhaustion rate of the mixed dyeing in two dye baths was higher than that for mixed dyeing in one dye bath. The poor exhaustion rate that was achieved when dyeing in a single dye bath indicated the incompatibility of both dyes when mixed in one dye bath. However, both methods achieved a rigid fixation as confirmed by washing-fastness test 105C6A01.

Aqueous-Solution-Processed Cu2ZnSn(S,Se)4 Thin-Film Solar Cells via an Improved Successive Ion-Layer-Adsorption-Reaction Sequence.

A facile improved successive ionic-layer adsorption and reaction (SILAR) sequence is described for the fabrication of Cu2ZnSn(S,Se)4 (CZTSSe) thin-film solar cells (TFSCs) via the selenization of a precursor film. The precursor films were fabricated using a modified SILAR sequence to overcome compositional inhomogeneity due to different adsorptivities of the cations (Cu+, Sn4+, and Zn2+) in a single cationic bath. Rapid thermal annealing of the precursor films under S and Se vapor atmospheres led to the formation of carbon-free Cu2ZnSnS4 (CZTS) and CZTSSe absorber layers, respectively, with single large-grained layers. The best devices based on CZTS and CZTSSe absorber layers showed total area (∼0.30 cm2) power conversion efficiencies (PCEs) of 1.96 and 3.74%, respectively, which are notably the first-demonstrated efficiencies using a modified SILAR sequence. Detailed diode analyses of these solar cells revealed that a high shunt conductance (Gsh), reverse saturation current density (Jo), and ideality factor (nd) significantly affected the PCE, open-circuit voltage (Voc), and fill factor (FF), whereas the short-circuit current density (Jsc) was dominated by the series resistance (Rs) and Gsh. However, the diode analyses combined with the compositional and interface microstructural analyses shed light on further improvements to the device efficiency. The facile layer-by-layer growth of the kesterite CZTS-based thin films in aqueous solution provides a great promise as an environmentally benign pathway to fabricate a variety of multielement-component compounds with high compositional homogeneities.

Mechanical properties of electrodeposited amorphous/crystalline multilayer structures in the Fe-P system

Amorphous/crystalline multilayer structures of Fe-P alloys were deposited electrochemically using the single bath technique. Hall-Petch behavior of microhardness with respect to sublayer thickness was observed down to a sublayer thickness of 15nm. For thinner sublayers, a hardness plateau was obtained. The transition at a sublayer thickness of 15nm coincides with the loss of the multilayer structure as observed in transmission electron microscopy. The transition is a possible result of a change in the amorphous to crystalline sublayer thickness ratio and the interface roughness development during the deposition process. Additionally, crack deflection at the interfaces was observed for the layered structures with small sublayer thickness in microbending experiments.

Microcanonical Szilárd engines beyond the quasistatic regime.

We discuss the possibility of extracting energy from a single thermal bath using microcanonical Szilárd engines operating in finite time. This extends previous works on the topic which are restricted to the quasistatic regime. The feedback protocol is implemented based on linear response predictions of the excess work. It is claimed that the underlying mechanism leading to energy extraction does not violate Liouville's theorem and preserves ergodicity throughout the cycle. We illustrate our results with several examples including an exactly solvable model.

Electrochemical, Structural and Magnetic Analysis of Electrodeposited CoCu/Cu Multilayers: Influence of Cu Layer Deposition Potential

The electrochemical, structural and magnetic properties of CoCu/Cu multilayers electrodeposited at different cathode potentials were investigated from a single bath. The Cu layer deposition potentials were selected as $$-\,0.3,\,\hbox {V}$$ $$-\,0.4\,\,\hbox {V}$$ , and $$-\,0.5\,\hbox {V}$$ with respect to saturated calomel electrode (SCE) while the Co layer deposition potential was constant at $$-\,1.5\,\hbox {V}$$ versus SCE. For the electrochemical analysis, the current-time transients were obtained. The amount of noble non-magnetic (Cu) metal materials decreased with the increase of deposition potentials due to anomalous codeposition. Further, current-time transient curves for the Co layer deposition and capacitance were calculated. In the structural analysis, the multilayers were found to be polycrystalline with both Co and Cu layers adopting the face-centered cubic structure. The (111) peak shifts towards higher angle with the increase of the deposition potentials. Also, the lattice parameters of the multilayers decrease from 0.3669 nm to 0.3610 nm with the increase of the deposition potentials from $$-\,0.3\,\hbox {V}$$ to $$-\,0.5\,\hbox {V}$$ , which corresponds to the bulk values of Cu and Co, respectively. The electrochemical and structural results demonstrate that the amount of Co atoms increased and the Cu atoms decreased in the layers with the increase of deposition potentials due to anomalous codeposition. For magnetic measurements, the saturation magnetizations, $$M_s$$ obtained from the magnetic curves of the multilayers were obtained as 212 kA/m, 276 kA/m, and 366 kA/m with $$-\,0.3\,\hbox {V}$$ , $$-\,0.4\,\hbox {V}$$ , and $$-\,0.5\,\hbox {V}$$ versus SCE, respectively. It is seen that the $$M_s$$ values increased with the increase of the deposition potentials confirming the increase of the Co atoms and decrease of the Cu amount. The results of electrochemical and structural analysis show that the deposition potentials of non-magnetic layers plays important role on the amount of magnetic and non-magnetic materials in the layers and thus on the magnetic properties of the multilayers.