Electrodeposition Of Thin Films Research Articles

(Invited) Optimization of Pulsed Electrodeposited Bi2Te3-Based Thin Films from DMSO Solution: Influence of Deposition Parameters, Electrolytic Bath Composition and Annealing

Bismuth telluride based alloys have been extensively investigated for thermoelectric power generation (TEG) and cooling near room temperature applications. To employ materials in TEG, requires materials with large Seebeck coefficient (S), high electrical conductivity (s) and low thermal conductivity (k) to achieve a high thermoelectric efficiency defined by zT = S2σ T/ k, where T is the absolute temperature at which properties are measured. Nanostructured materials, specifically mesoscale composites showed improved zT values due to the reduction in thermal conductivity without reducing the electrical conductivity [1]. However, most of these materials are being fabricated through alloying using high temperature and pressure [2, 3], and thereby not scalable in terms of Si based fabrication processes. The growing demand of miniaturized room temperature thermoelectric devices based on bismuth telluride alloys has led to research focused on synthesizing thin films, in particular, using electrochemical deposition. Electrodeposition of thin films is a facile, low cost process without the need for sophisticated high-vacuum equipment in contrast to the physical deposition methods [4-6], which is also Si-Fab compatible. The electrodeposition of bismuth telluride alloy films has been reported in the literature [2-4]. The challenge, however, is to achieve bulk-like thermoelectric properties in the electroplated thin films. A comprehensive analysis of the literature demonstrates that the composition of bismuth telluride alloys plays a pivotal role in determining their thermoelectric properties [3, 4]. Schumacher et al., reported that the Seebeck coefficient of (BixSb1-x)2Te3 thin film increases after annealing the films in tellurium (Te) atmosphere for 60 h which is attributed to the improved Te content in the annealed films [4]. The objective of the present work is to synthesize electrodeposited p and n-type bismuth telluride alloy based thin films and to optimize the thermoelectric properties similar to the bulk by tuning the composition of the films. Here, we studied comprehensively the influence of electrolytic bath content, deposition potential and annealing on the composition of as-deposited films and in turn on the thermoelectric properties. The impact of annealing temperature on the films composition, structure and the Seebeck coefficient is discussed. The annealed p- and n-type thin films exhibit a room temperature Seebeck coefficient of about 175 and -160 μVK-1 respectively, which is similar to the bulk materials [3]. Structural and chemical investigations of the as-deposited and annealed thin films are performed with X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Thus, we synthesize the electroplated thin films based on bismuth telluride and optimize its composition and micro-structure by adjusting the deposition parameter and annealing temperature to enhance the thermoelectric properties. Acknowledgements This work is financially supported by Enterprise Ireland and Analog Devices, Limerick, Ireland under Innovation Partnership project IP-2012-0197.

Electrodeposition of Cu-Ag Alloy Thin Films Directly on W Diffusion Barrier By Controlling Complexing Agents and Organic Additives

Cu as an excellent electrical conductor has been used for interconnect in Si-based microelectronic devices. Recently Cu alloys instead of Cu have emerged as interconnect material for future microelectronic device fabrication because higher adhesion strength to foreign materials, larger resistance to electromigration, and improved electrical conductivity are required in very narrow interconnect lines. It is known that Cu-Ag alloy among Cu alloys has beneficial properties such as higher electrical conductivity, better formability, higher mechanical strength, and better resistance to electromigration than pure Cu. In this research, we investigate the effect of electrodeposition parameters on the nucleation and growth of Cu-Ag alloy nano-nuclei and the formation of thin, smooth Cu-Ag alloy thin film. Cu-Ag alloys are electrodeposited directly on W diffusion barrier without employing a Cu seed layer. Area density, size, and morphology of Cu-Ag alloy nano-nuclei influence the microstructure, surface roughness, and thickness of Cu-Ag alloy thin film formed on the W diffusion barrier. Sophisticated control of chemical equilibrium of electrolyte is carried out by managing the concentration and type of complexing agent and organic additives. Chelation behavior of Cu and Ag with complexing agent is also studied according to pH of electrolyte. Reduction rate and chemical composition of electrodeposited Cu-Ag alloy are controlled under diffusion-controlled deposition conditions.

In-Situ Stress Measurements during Cobalt Electrodeposition on (111)-Textured Au

The electrodeposition of Cobalt1-3 thin films has attracted much attention in recent years owing to its uses in both magnetic recording as well as alkaline fuel cell catalysis. The evolution of residual stress during thin film growth is complex, having dependence on the microstructure, growth conditions, and material parameters. However, numerous studies have led to a better understanding and mechanisms of residual stress are beginning to emerge. During film deposition, stress is small in the initial stages, eventually becoming tensile during the coalescence of nuclei into a continuous film. However, as films become increasingly thicker and the height becomes more uniform, the stress often assumes a constant steady-state value. Models have been developed that treat this steady state stress as a competition between the tensile and compressive stress generation mechanisms that are governed by atomic mobility, microstructure, and deposition rate4. In this study, the stress was measured with optical wafer curvature techniques that can be used during electrodeposition to determine real-time stress. The measured curvature is proportional to the product of the average biaxial stress (stress-thickness product) and the film thickness vis-à-vis the Stoney equation. Figure 1 shows a cyclic voltammogram (CV)/ stress thickness curve for the deposition of Co on (111) textured Au in 0.1 M NaClO4 + 0.001 M Co(ClO4)2. The CV shows a small peak at -1.0 V, due to the reduction of H+ on the Au surface followed by the reduction of Co at -1.2 V, with increasing overpotential eventually leading to HER due to H2O reduction. The anodic crossover on the return sweep occurs at a potential of -1.08 V, which is presumably close to the equilibrium value of -1.03V. The accompanying stress curve shows that prior to Co reduction, there is a slight increase in the tensile stress owing to electrocapillarity as well as the desorption of ClO4 - from the Au surface. Upon the initial reduction of Co, the stress initially becomes compressive (about -0.2 N/m) before turning back to the tensile direction. The negative electric charge associated with the peak in the compressive stress is about 500 µC/cm2. Considering a 2-electron reduction process, this corresponds to less than 1 monolayer of cobalt metal, assuming that 590 µC/cm2 is required to deposit an incommensurate close-packed monolayer The stress-thickness reaches a maximum of ~ +1.5 N/m under cathodic scan. It is interesting to note that little stress change is observed at potentials more negative than -1.4 V, reflecting the very low faradaic efficiency for Co deposition once H2O is able to be reduced. On the reverse sweep, additional tensile stress (+3.25 N/m) is produced until dissolution of Co occurs further along the anodic cycle. This talk will examine the nature of the stress generation in Cobalt electrodeposited films with focus on overpotential and structure.

Electrodeposition of Ordered Copper Germanide from an Alkaline Tartrate-Complexed Electrolyte

Copper is widely used for contacts and interconnects in Si-based semiconductor devices. Copper, however, is regarded as the fastest interstitial-diffusing element in Si with a diffusivity of ~ 10-8 cm2/s at room temperature [[i]]. The diffusion of copper into surrounding materials would significantly degrade their properties and the performance of semiconductor devices. Therefore, a barrier metal layer is necessarily required to completely surround all copper interconnects, which complicates the device fabrication. Recently, copper germanide (ɛ-Cu3Ge) has received much attention as a promising candidate material for contacts and interconnects due to its remarkably low resistivity of 5.5 μΩ cm at 300K [[ii]], which is only approximately three times the resistivity of pure Cu films. In particular, Cu3Ge is stable up to a temperature of 450°C, thus impeding the diffusion of Cu from the film into the surrounding materials, making it an excellent candidate for interconnects in Si-based devices [[iii]]. In the present work, the electrochemical deposition of ɛ-Cu3Ge thin films from an alkaline tartrate-complexed electrolyte [[iv]] was thoroughly investigated. Primarily, the partial (single element Cu and Ge deposition) and net (Cu-Ge alloy co-deposition) processes occurring in such electrolyte were studied by means of cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM) and electrochemical impedance spectroscopy (EIS) techniques. Subsequently, the electrodeposition of Cu-Ge thin films was realized in potentiostatic mode at various selected potentials. The morphology, composition and microstructure of as-deposited Cu-Ge thin films were characterized, and the results reveal that the Ge content in the deposits increases with decreasing applied potential in a sigmoidal manner, leading to a gradual disorder-order phase transformation of Cu-Ge alloy from a disordered face-centered-cubic solid solution (α-phase) to an ordered orthorhombic Cu3Ge intermetallic compound (ɛ-phase). Combining the morphological, compositional and structural characteristics of electrodeposited Cu-Ge thin films with the processes kinetics studies, a possible mechanism of Cu-Ge induced codeposition was postulated. The dependence of resistivity of as-deposited Cu-Ge thin films on Ge content was also examined, which exhibits a non-monotonic behavior. A minimum value was found around stoichiometric Cu3Ge, which corresponds to the completion of the disorder-order transformation. The ɛ-Cu3Ge thin film displays a resistivity of 7.5 μΩ cm-1 (~50 nm) and 25 μΩ cm-1 (~1 μm), increasing with the deposition duration, which is believed due to the progressive incorporation of O into the films. In order to overcome this limitation, the effect of the bath temperature and pH on Cu-Ge electrodeposition kinetics, composition and microstructure were investigated, and optimal electrodeposition conditions for ɛ-Cu3Ge were identified. [i] M.O. Aboelfotoh, H.M. Tawancy, L. Krusin-Elbaum, Correlation of electrical-resistivity anomalies and crystal structure in copper-germanium thin-film alloys, Appl. Phys. Lett. 63, 1622 (1993). [ii] L. Krunsin-Elbaum, M.O. Aboelfotoh, Unusually low resistivity of copper germanide thin films formed at low temperatures, Appl. Phys. Lett. 58, 1341 (1991). [iii] M.A. Borek, S. Oktyabrsky, M.O. Aboelfotoh, J. Narayan, Low resistivity copper germanide on (100) Si for contacts and interconnections, Appl. Phys. Lett. 69, 3560 (1996). [iv] A. Joi, R. Akolkar, U. Landau, Pulse plating of copper germanide, Appl. Phys. Lett. 102, 134107 (2013).

Electrodeposition of ZnO-RGO thin film for determining Hg(II) in water samples

Electrodeposition of ZnO-RGO thin film for determining Hg(II) in water samples

Electrochemical cell for in situ electrodeposition of magnetic thin films in a superconducting quantum interference device magnetometer.

An electrochemical cell is designed and applied for in situ electrodeposition of magnetic thin films in a commercial SQUID magnetometer system. The cell is constructed in such a way that any parasitic contribution of the cell and of the substrate for electrodeposition to the magnetic moment of the deposited film is reduced to a minimum. A remanent minor contribution is readily taken into account by a proper analysis of the detected signal. Thus, a precise determination of the absolute magnetic moment of the electrodeposited magnetic film during its growth and dissolution is achieved. The feasibility of the cell design is demonstrated by performing Co electrodeposition using cyclic voltammetry. For an average Co film thickness of (35.6 ± 3.0) atomic layers, a magnetic moment per Co atom of (1.75 ± 0.11) μ(B) was estimated, in good agreement with the literature bulk value.

Electrodeposition of PbTe thin films: electrochemical behavior and effect of reverse pulse potential

This paper reports on the voltammetric behavior of gold substrates in acidic nitrate electrolytes containing HTeO2+ and Pb2+. Particular anodic behavior is highlighted and studied by anodic stripping experiments, demonstrating that the presence of PbTe dendrites induces an additional anodic peak prior to the dissolution of bulk PbTe. The diffusion coefficients of Pb2+ and HTeO2+ were measured in order to adjust their respective concentration in the electrolyte. Diffusion of Pb2+ being slightly faster than HTeO2+, optimal concentrations were calculated to be 4.1mM Pb2+ for 5mM HTeO2+. For steady state potentiostatic deposition, Pb is underpotentially deposited onto overpotentially deposited Te0 from -175mV and its content in the deposit slightly increases with the applied overpotential. However, increasing the overpotential also induces dendritic morphologies. In contrast, reverse pulse deposition can lead to the formation of spherical assemblies of hollow trigonal nanorods with high specific area. However, it strongly decreases the Pb content in the film.

In Situ Ftirs Study of Glycine Effects on Cobalt Electrodeposition on Gold Electrodes

INTRODUCTION The presence of certain chemical species (additives) in plating baths can significantly influence the metal electrodeposition process. Thus, the electrodeposits may show different properties, due to altered morphology, structure or composition. Glycine is an additive present in many electrolytic solutions for electrodeposition of Cobalt thin films and alloys (which are interesting due to their magnetic properties). The properties of some Co-based alloys obtained from glycine-containing baths are well documented [1,2], but more fundamental-oriented studies of the exact role of the aminoacid are lacking. In this paper, we report some spectroelectrochemical studies using external reflection FTIR spectroscopy, method that can be used to obtain microscopic information on the interfacial region, assess the possibility of glycine adsorption at negative electrode potentials, and verify possible alterations in composition of solutions containing cobalt and glycine. EXPERIMENTAL The spectroelectrochemical experiments were carried out in solutions containing CoSO4 (0.050 mol L-1), Na2SO4 (0.30 mol L-1) and glycine (0.20 mol L-1), with pH values of 3, 4, and 6. A gold electrode (8 mm diameter) was used as working electrode. The electrode potentials are referred to a Ag|AgCl (3M KCl) reference electrode, which was separated from solution via Luggin capillary. The spectroelectrochemical cell had a flat CaF2window at its bottom, to which the gold electrode was pressed against. Experiments consisted of a potential step from +0.20 V (E0) to the desired sample potential (ES, with ES<E0), where spectra were acquired. The absorbance unit is given by A = -log(I/I0), with I0being the radiation intensity at the reference potential (+0.20 V). RESULTS AND DISCUSSION The hydrogen evolution reaction (HER) imposed a lower limit for the electrode potentials that could be studied. At these limit potentials, the H2evolution starts to disturb the thin layer. In our system, the potential limits were -0.55 V for pH 3, and -0.75 V for pH 6. Within these limits, no signs of adsorption of glycine on the Au electrode were detected with the experimental conditions and configuration utilized. Changes in composition of the solution in the thin layer were detected and depended on pH, as expected. For solutions in pH 3 the HER is strongly intensified in comparison to glycine-free solutions, this being attributed to appearance of a pH buffer, as a significant fraction of glycine is in the cation form (protonated carboxyl). During the potential steps, negative absorption bands assigned to the cation and positive bands assigned to the zwitterion form were observed in the spectra, confirming perturbation of the equilibrium. The use of glycine in this pH value is not common in plating baths, but may be useful in Co alloys electrodeposition according to some authors [2]. For pH 4, signs of glycine coordination to Co2+ are observed. The absorption bands assigned to symmetric and asymmetric carboxyl stretching in the zwitterion appear in lower wavenumbers when sufficiently negative potentials are applied (-0.60 V, Figure 1), this evidences complex formation [3]. In the initial pH value of 4, cobalt-glycine complexes are absent. Therefore, the increase in thin layer pH should be substantial (at least to pH 5) during electrode polarization. Similarly, in pH 6 solutions, the infrared spectra show an increase in the concentration of cobalt-glycine complexes at negative potentials. CONCLUSIONS In the range of electrode potentials investigated, glycine molecules do not undergo redox reactions, and no signs of adsorption on polycrystalline Au electrode were detected. For low pH values in which a considerable amount of glycine is in its cation form, the HER is greatly enhanced. In pH 4, the increase of pH in the thin layer during potential step to -0.60 V was high enough to promote Co2+coordination with glycine. In pH 6, a rise in the concentration of the complexes was detected, probably also due to HER. ACKNOWLEDGEMENTS We thank Professor Mauro C. dos Santos and Júlio C. M. da Silva for useful discussions. We thank Fapesp and CNPq for the financial support. REFERENCES 1. J. C. Wei, M. Schwartz e K. Nobe. J. Electrochem. Soc. 155(10), D660 (2008). 2. O. Ergeneman, K. M. Sivaraman, S. Pané, E. Pellicer, A. Teleki, A. M. Hirt, M. D. Baró, B. J. Nelson, Electrochim. Acta 56, 1399 (2011). 3. K. Nakamoto, Y. Morimoto, A. E. Martell, J. Am. Chem. Soc. 83, 4528 (1961). Figure 1

Impact of Thiourea Addition on Morphological and Structural Characteristics of Electrodeposited ZnO Thin Films Using Nitrate Aqueous Solutions

Thin films of ZnO find a number of important applications such as chemical sensors, light emitting devices, photosensors, solar cells and dye-sensitized solar cells [1]. Electrodeposition is one of the promising techniques for cost reduction and large area applications and specially suited to solar cells. Electrodeposition of crystalline ZnO thin films from aqueous solution is either based on electroreduction of nitrate or dissolved oxygen [2]. Large numbers of studies have been devoted to growth by electrodeposition for the synthesis of nanostructured ZnO layers. It has been shown that is possible to tune the morphology and density of ZnO layers by varying the electrolyte composition or the concentration of the chemical species present in solutions. In this study the effect of the action of thiourea on the growth mechanism, crystal structure and morphology of ZnO layers will be investigated. The deposition of zinc oxide is investigated using zinc nitrate aqueous solutions. The effect of thiourea concentration has been first evaluated from a theoretical solution chemistry analysis by mean of solubility diagrams and repartition of the species showing that even if zinc-thiourea complexation constants are quite low, zinc ions are consistently complexed by the thiourea for pH<6. Moreover, standard equilibrium potentials have been estimated from the Gibbs free energy values at 80 °C in order to predict the reactions which are most likely to occur. Cyclic voltammetry studies are then carried out using SnO2:F (FTO) and ZnO:Al-coated glass as a function of the thiourea concentration. The main reduction wave corresponds to simultaneous nitrate reduction and ZnO electrodeposition (Reaction 1)[3]: Zn2+ + NO3 - + 2 e- → ZnO + NO2 - (1) A shift of the reduction wave is observed as soon as thiourea is added into the electrolyte. In order to visualize this trend, Fig. 1 shows the potential as a function of the thiourea concentration recorded for a fixed current density value in the voltamperometric curves. The films have been grown at a potential of -1.5 V/MSE for 5 minutes for increasing thiourea concentrations between 0 M and 1 M on both the substrates. The films are characterized through XRD, SEM and EDX analysis. Results show that the concentration of thiourea has a significant influence on the morphology and growth rate of films. XRD analysis shows that the film is composed of well-crystallized ZnO. EDX analysis highlights that Zn and O are the main components of the films with a very low incorporation of sulfur. SEM analysis indicates that the surface morphology is clearly evolving from a classical platelet ZnO structure, to nodular morphology for increasing thiourea concentrations. Fig. 2 shows the cross section of a deposited ZnO film in presence of thiourea. The film is about 4 μm thick and presents a nanoporous structure. In fact, as soon as 0.05 M of thiourea is added in the electrolyte, the thickness of the films seems to be much larger than expected from the apparent Faradaic efficiency (Fig. 3). Based on these results it seems that thiourea could be a suitable additive for the formation of nanoporous films. The mechanism of the formation of the films will be discussed in detail.

Delafossite CuFeO2 thin films electrochemically grown from a DMSO based solution

This study shows the results obtained in the direct electrodeposition of CuFeO2 thin films from a DMSO based solution. First, a detailed electrochemical study was carried out in order to determinate the best condition for the CuFeO2 electrodeposition. The films were obtained potentiostatically from a 0.01M CuCl2+0.005M Fe(ClO4)3+0.1M LiClO4 solution in the presence of molecular oxygen at 50°C onto FTO/glass substrates. In all cases, the time of electrodeposition was 1000s. The grown films presented a yellow-reddish color and exhibit an homogeneous aspect. Analyses of composition carried out through EDS, shown that a stoichiometric composition (atomic relation Cu:Fe=1:1) is obtained at a potential of –0.6V. However, as-grown films analyzed through XRD experiences did not evidence the presence of CuFeO2 compound presumably because it is amorphous. An annealing treatment at 650° C for 30minutes in an argon atmosphere was necessary to transform the solid phase of the as grown films in crystalline CuFeO2. Furthermore, the presence of CuFeO2 has been confirmed through XPS analyses. UV-vis analyzes shown a ladder-like appearance due to the presence of several absorption edges from the IR to the UV spectrum region. The most clearly determined were a direct-like edge at the IR: Eg(IR)=1.64eV. However, several absorption edges in the visible (Egdir(vis)=2.35eV, and Egind(vis)=2.03eV) and UV beginning (Egind(UV)=3.37eV) spectrum region also were observed.

Synthesis and performance of Zn–Ni–P thin films**Project support by the Partnership Romanian Research Program (PNCDI2), CORZIFILM Project nr.72-221/2008-2011 and “EU (ERDF) and Romanian Government” that allowed for acquisition of the research infrastructure under POS-CEEO 2.2.1 project INFRANANOCHEM-Nr.19/01.03.2009.

The electroplating of Zn–Ni–P thin film alloys from a sulfate bath containing phosphoric and phosphorous acid was investigated. The bath composition and the deposition parameters were optimized through Hull cell experiments, and the optimum experimental conditions were determined (pH = 2, temperature = 298–313 K, zinc sulfate concentration = 30 g·L−1, EDTA concentration = 15 g·L−1, and current density, = ,1.0–2.0 A·dm−2). The SEM analysis of the coating deposited from the optimum bath revealed fine-grained deposits of the alloy in the presence of EDTA. Optical microscopy analysis indicated an electrodeposited thin film with uniform thickness and good adhesion to the steel substrate. The good adherence of the coatings was also demonstrated by the scratch tests that were performed, with a maximum determined value of 25 N for the critical load. Corrosion resistance tests revealed good protection of the steel substrate by the obtained Zn–Ni–P coatings, with values up to 85.89% for samples with Ni contents higher than 76%. The surface analysis of the thin film samples before and after corrosion was performed by X-ray photoelectron spectroscopy (XPS).

Synthesis and Characterization of Au-CdS Composite Thin Films for Photoelectrochemical Sensing of Hg&lt;sup&gt;2+&lt;/sup&gt; Ions

This article presents a simple method for fabrication of Au-CdS composite thin films onto indium-tin-oxide (ITO) coated glass substrates. The method starts with electrodeposition of CdS thin films onto ITO substrates and followed by spontaneous growth of Au nanoparticles onto the CdS surface in solutions containing AuCl4- ions. X-ray diffraction (XRD) and UV-vis spectroscopy were used to investigate the Au-CdS thin films. The photoelectrochemical property and sensing for Hg2+ ions of the Au-CdS/ITO were studied. The electrode exhibits a low limit of detection of 2.5 μM and a high selectivity for Hg2+ ions, even in the presence of a large excess (1000-fold) of other metal (Na+, K+, Ca2+, Mg2+, Cd2+, Pb2+, and Zn2+) ions.

Electrodeposition of CdSe photoabsorber thin films in the presence of selected organic additives

Photoabsorbing CdSe semiconductive thin films were prepared by cathodic electrodeposition onto titanium substrates from an acidic aqueous electrolytic bath, containing some selected, commercially available organic salts as additives, specifically monosodium l-glutamate and choline chloride. The products obtained were fully characterized with XRD and SEM–EDAX techniques and their photoelectrochemical behavior was studied using a photoelectrochemical cell (PEC). It is observed that the use of both additives leads to more uniform and in many cases to better crystallized deposits. All films, taken in the presence of the additives, exhibit some differences in their semiconductive behavior, in comparison to the pure CdSe ones. However, the addition of monosodium l-glutamate salt into the bath brought about a clear improvement in photoresponse of the deposits, whereas the use of the choline chloride salt clearly led to a deterioration of their photoconductivity. It is considered that the organic ions of the salts (l-glutamate anion and choline cation) are potentially adsorbed on the CdSe deposits, thus introducing crystal defects, which modify the electric properties of the final products.

Electrodeposition of ZnSe thin film and its photocatalytic properties

ZnSe is an important and excellent II–VI semiconductor material, which has the direct transition band structure. In this paper, ZnSe thin films were prepared by electrochemical deposition method, and the effects of deposition potential and deposition time on the photocatalytic properties of the ZnSe thin films were studied systematically. The results showed that more positive potential and longer deposition time lead to the decrease of degradation efficiency. The deposition time has a significant effect on the degradation efficiency. The film which was prepared at the potential of −1V (versus Pt) for 1h showed the highest degradation efficiency, and methyl orange could be completely degraded within 5h. The mechanisms for the photocatalytic activities were also discussed.

Controlled electrodeposition of nanostructured Pd thin films from protic ionic liquids for electrocatalytic oxygen reduction reactions

Nanostructured Pd thin films are prepared from protic ionic liquids via hydrogen-assisted electrodeposition for oxygen reduction reactions.

Electrodeposition and Characterization of Copper Oxide Thin Films for Solar cell Applications

Copper oxide thin films are being considered in thin film solar cells for its unique photovoltaic properties. Electrodeposition is one of the cheapest processes to deposit copper oxide thin films. In this study, copper oxide was electrodeposited on the copper substrate and gold plated glass substrate in an electrolyte bath containing 0.2M CuSO4.5H2O, 3M lactic acid and NaOH. A Potentiostat/Galvanostat with silver chloride electrode (Ag/AgCl) as a reference electrode was used for elctrodeposition. During deposition, the bath temperature and pH were maintained 600C and 12-12.5 respectively. Copper oxide was deposited at different potentials and deposition time. The films deposited at different electrodeposition conditions were characterized by Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS). The optical band gap was determined from the films deposited on gold plated glass substrate using Ultraviolet-Visible Spectroscopy. From visual inspection it was found that copper oxide film was black and adherent on copper substrate. In gold coated glass substrate copper oxide film was also black but bonding between the substrate and copper oxide film was not good. The SEM study reveal that the films become more compact and grain sizes of copper oxide films decreases at more negative potentials in deposition potential range. EDS analysis shows that percentage of oxygen in the copper oxide films increases with more negative potentials at the deposition potential range. It was found that with increase of time more adherent and uniform film thickness occurs. The variation of the thickness of copper oxide films with different deposition parameters was analyzed.

Study of electrode processes and deposition of cobalt thin films from ionic liquid analogues based on choline chloride

The cathodic processes of cobalt ion in ionic liquids consisting in binary mixtures of choline chloride (ChCl) with urea, ethylene glycol, malonic acid or oxalic acid were investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The as-received hexahydrate cobalt chloride has been the precursor of cobalt ionic species. It was found that the reduction mechanism of Co2+ in ChCl-urea and ChCl-ethylene glycol is a quasi-reversible (or with high degree of irreversibility at high scan rate) and diffusion controlled process, whereas in ChCl-carboxilic acid solvents the cathodic process of Co2+ is overlapped with reduction of protons. By using Pt and vitreous carbon electrodes, one has computed the value for the Co2+ diffusion coefficient in ChCl-urea at 80 °C; in comparison with values obtained in aqueous solutions, this is up to two orders of magnitude lower. The paper also describes preliminary experiments concerning electrodeposition of cobalt thin films on copper substrate from the four ionic liquid analogue solvents containing choline chloride. The crystalline morphology and structural constitution of Co deposits were examined by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Good results regarding the quality and cobalt content in films were obtained for Co deposits using ChCl-urea or ChCl-ethylene glycol mixtures as solvents. The behaviour of Co films grown from these media was typical for a ferromagnetic material.

Electrodeposition of thermoelectric Bi2Te3 thin films with added surfactant

Bismuth telluride (Bi2Te3) thin films were electrodeposited at room temperature from nitric baths in the presence of a surfactant, cetyltrimethylammonium bromide (CTAB). Nearly stoichiometric Bi2Te3 thin films were obtained from electrolytes containing 7.5 mM Bi(NO3)3. The surface morphology and mechanical properties of the electrodeposited thin film were improved by the addition of CTAB to the electrolyte, while the electrical and thermoelectric properties were preserved. Post-deposition annealing in a reducing environment did not improve the electrical and thermoelectric properties, possibly because the change in the microstructure of the Bi2Te3 thin film was too small.

Effects of temperature in electrodeposition of ZnTe thin films

ZnTe thin films have been deposited at various temperatures about 110–160 °C onto FTO-coated glass substrates by low-cost, easy and simple non-aqueous electrodeposition method for using it in solar cell application. The optimized growth conditions are chosen for ZnTe layers by investigating the photoelectrochemical, optical, structural and morphological properties of the deposited films. Optical measurement of the p-type ZnTe films have higher transmittance in the UV–Visible region; moderate transmittance in the visible region and moderate to lower transmittance in the visible–infrared region and have higher absorbance in the middle of the visible region to near infrared region. Band gap values were estimated to vary from 2.23 to 1.8 eV for the ZnTe films deposited at different conditions. Band gap of ZnTe decreases when the films annealed at 300, 350 and 425 °C in nitrogen environment. From the XRD and SEM study the films deposited from 110 to 150 °C were elemental Te film but Zn was not deposited at this temperature. When the deposition temperature was increased to 160 °C and annealing at 425 °C, the films were found to be polycrystalline ZnTe films with (111) preferential orientation of the cubic structure and appeared dense crack-free surfaces with regular granular shaped grains without any cauliflower like appearance. After annealing and all characterization it was concluded that ZnTe thin film can be deposited at 160 °C for 40 min at −0.75 V.

Electrodeposition of kesterite thin films for photovoltaic applications: Quo vadis?

This paper aims at providing an updated overview of the main achievements in the development of solar cells based on Cu2ZnSn(S,Se)4 (CZTS(Se)) kesterite absorbers obtained by electrodeposition. Although undoubtedly challenging, the ultimate goal is to learn from the past works and build a solid framework for future advances in this field. What is the reason for the lower efficiency of electrodeposited CZTS(Se)-based devices (8%) compared to the world record efficiency achieved with a hydrazine-based solution approach (12.6%)? Can this gap be filled, or there are intrinsic limitations for this achievement? The review is divided into the three main electrodeposition approaches: sequential elemental layer, alloy co-deposition, and chalcogenide co-deposition. It is argued that considerable technical challenges must be overcome for the latter approach to be successfully applied. Plot of the record power conversion efficiencies of kesterite sulfide-based solar cells obtained by electrodeposition (hollow dots), and world record efficiency of CZTS(Se)-based devices (full dots). The dashed line shows the 15% minimum efficiency threshold considered relevant for potential industrial application.