Electrodeposition Of Thin Films Research Articles

Electroplating of CdTe Thin Films from Cadmium Sulphate Precursor and Comparison of Layers Grown by 3-Electrode and 2-Electrode Systems

Electrodeposition of CdTe thin films was carried out from the late 1970s using the cadmium sulphate precursor. The solar energy group at Sheffield Hallam University has carried out a comprehensive study of CdTe thin films electroplated using cadmium sulfate, cadmium nitrate and cadmium chloride precursors, in order to select the best electrolyte. Some of these results have been published elsewhere, and this manuscript presents the summary of the results obtained on CdTe layers grown from cadmium sulphate precursor. In addition, this research program has been exploring the ways of eliminating the reference electrode, since this is a possible source of detrimental impurities, such as K+ and Ag+ for CdS/CdTe solar cells. This paper compares the results obtained from CdTe layers grown by three-electrode (3E) and two-electrode (2E) systems for their material properties and performance in CdS/CdTe devices. Thin films were characterized using a wide range of analytical techniques for their structural, morphological, optical and electrical properties. These layers have also been used in device structures; glass/FTO/CdS/CdTe/Au and CdTe from both methods have produced solar cells to date with efficiencies in the region of 5%–13%. Comprehensive work carried out to date produced comparable and superior devices fabricated from materials grown using 2E system.

One step electrodeposition of Cu2ZnSnS4 thin films in a novel bath with sulfurization free annealing

Cu2ZnSnS4 (CZTS) is a quaternary kesterite compound with suitable band gap for thin film solar cells. In most electrodeposition-anneal routes, sulfurization is inevitable because the as-deposited film is lack of S. In this work, a novel green electrolyte was designed for synthesizing CZTS thin films with high S content. In the one-step electrodeposition, K4P2O7 and C7H6O6S were added to form complex with metallic ions in the electrolyte, which could attribute to co-deposition. The as-deposited film obtained high S content satisfying stoichiometry. After a sulfurization free annealing, the continuous and uniform CZTS thin film was obtained, which had pure kesterite structure and a suitable band gap of 1.53eV. Electrodeposition mechanism investigation revealed that the K4P2O7 prevented the excessive deposition of Cu2+ and Sn2+. The C7H6O6S promoted the reduction of Zn2+. So the additives narrowed the co-deposition potentials of the metallic elements through a synergetic effect. They also promoted the reduction of S2O32− to ensure the co-deposition of the four elements and the stoichiometry. The sulfurization free annealing process can promote the commercialization of CZTS films and the successful design principle of environmental friendly electrolytes could be applied in other electrodeposition systems.

A Mixture of Ionic Liquid and Ethanol Used for Galvanostatic Electrodeposition of CuInxGa1-xSe2 Thin Films

A mixture of 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4) and ethanol is used for synthesizing CuInxGa1-xSe2 (CIGS) thin films by one-step electrodeposition. The conductivity and electrochemical windows of the mixtures with different volume ratios of ethanol are studied, and Fourier transform infrared spectroscopy spectra are recorded for investigating the interaction between BMImBF4 and ethanol, which indicates that the cations and anions of the ionic liquid interact with ethanol molecule. The electrochemical behaviors of Cu-In-Ga-Se systems are investigated with different ethanol volume fraction. Quantum chemical calculations and molecular dynamic simulations are introduced to study the electronic properties and orbital information of mixtures and electrochemical behaviors of Cu-In-Ga-Se in the mixture. CIGS thin films are characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy in terms of morphology and composition, and by X-ray diffraction and Raman regarding crystal structure. The results show ethanol content has great influences on the electrochemical behaviors of Cu-In-Ga-Se systems as well as the composition and morphology of CIGS thin films. The deposited CIGS thin films are high crystalline quality p-type semiconductor with a bandgap of 1.28 eV after annealed. The mixture can be a promising candidate in industrial application of ionic liquids for electrodeposition of CIGS thin films, even other metals, alloys and semiconductors.

Cobalt(ii) containing liquid metal salts for electrodeposition of cobalt and electrochemical nanoparticle formation.

Cobalt(ii)-containing liquid metal salts (LMS) with N-alkylimidazole ligands and bis(trifluoromethanesulfonyl)imide (bistriflimide, Tf2N-) or methanesulfonate (mesylate, OMs-) anions were synthesized and characterized. The chain length of the alkyl side chain on the imidazole ligand was varied. All compounds were characterized using CHN analysis, DSC and FTIR measurements. Single-crystal X-ray diffraction measurements were performed on six of the compounds for which single crystals of good quality could be obtained. All cobalt(ii) centers are six-coordinate with the N-alkylimidazole ligands in an octahedral configuration and the anions are non-coordinating. The same coordination environment was observed by EXAFS measurements on cobalt(ii) liquid metal salts in the liquid state. The electrochemical properties of the compounds with the lowest melting temperatures were investigated using cyclic voltammetry. It was found that part of the current was consumed in the electrodeposition of cobalt, whereas the other part of the current was consumed in the electrochemical formation of cobalt(0) nanoparticles.

Electrodeposition of Aluminum onto Copper-Coated Printed Circuit Boards

The electrodeposition of aluminum thin films onto copper-coated printed circuit boards from aluminum chloride-trimethylphenylammonium chloride ionic liquids is studied. Various electrodeposition methods with different surface pretreatment procedures were investigated and compared to optimize the deposited aluminum morphology and properties. For the same amount of charge, a pulse current deposition approach applied at a low duty cycle of 10% allowed the use of higher deposition current densities, leading to finer and more compact aluminum deposits compared with those produced by constant potential and constant current deposition techniques. Pulse current deposition with various peak current densities of −25 mA/cm2 to −65 mA/cm2 was conducted over a temperature range of 20°C to 60°C. At a moderate temperature of 40°C, the electrodeposited aluminum layer was the most adherent. An increase of peak current density did not have an obvious effect on the deposit morphology, but it led to an increased amount of both deposited aluminum and incorporated impurities (oxygen and chloride). At room temperature, the electrical resistivity of the copper-coated printed circuit boards with deposited aluminum decreased as the peak current density for aluminum deposition increased.

Electrodeposition and Capacitance Measurements of WS2 Thin Films

Polycrystalline WS2 thin films were fabricated by electrodeposition onto ITO from an electrolyte containing 4 mM (NH4)2WS4 + 0.1 M LiClO4 in acetonitrile, followed by a two-stage sulfurization and crystallization procedure at elevated temperature in a tube furnace. The as-deposited films had a S:W stoichiometric ratio of ∼2.8, which decreased to 2 after annealing. X-ray diffraction indicates that the annealed WS2 films crystallize into the 2H polytype with an average grain diameter of ∼22 nm. The capacitance of WS2 thin films was studied in different electrolytes, and the maximum capacitance observed was 1980 F/g, which decreased to 1610 F/g after 1000 cycles, for 10 nm thick WS2 in 1.0 M aqueous LiClO4. Capacitance studies as a function of WS2 film thickness yield different behavior in electrolytes containing Li+ and Na+, with the capacitance per unit area plateauing at a considerably higher film thickness in Li+-containing electrolytes. This suggests that the active depth for charge storage increases due to the smaller ionic radius of Li+.

Optimization of the Sandblasting Process for a Better Electrodeposition of Copper Thin Films on Aluminum Substrate by Feedforward Neural Network

The influence of a proper surface preparation is essential for a better adhesion of copper thin films on aluminum substrate. In this work, the surface properties of the aluminum substrate have been modified through sandblasting process, in order to influence the quality of electroplating. To evaluate the correct adhesion of the thin film to the substrate non-destructive measurements of diffusivity by infrared thermography have been made. A combining of a feedforward artificial neural network (FFANN) and an external optimized algorithm (EOA) is proposed to optimize the substrate surface preparation process. A FFANN model is developed to map the complex non-linear relationship between the surface process conditions of the substrate and the thermal diffusivity of the electroplated sample. A good performance of the FFANN model is achieved. An EOA is used for the optimization of the sandblasting process conditions, in order to maximize the adhesion of the thin film to the substrate.

Effect of different complexing agents on Pb–Co thin-film electrodeposition

Lead (Pb)–cobalt (Co) films have been studied by several researchers regarding their electrocatalytic activity when used as anodes in oxygen evolution reactions. Although several authors have suggested that the electrodeposition technique is the best alternative to Pb–Co film deposition, the process is complex. In many cases, the use of complexing agents facilitates the electrodeposition of multi-element coatings; but this performance has not been reported in the literature for Pb–Co electrodeposition. In this work, the effect of three different complexing agents (tartaric acid, sodium citrate, and ascorbic acid) on Pb–Co electrodeposition was studied. Speciation diagrams and polarization curves have been used to determine the reduction potentials of Pb2+ and Co2+ ions in the different systems studied. Speciation diagram predictions were incapable of revealing all species present in solution and for an accurate prediction of the actual electrochemical functioning of the system; the information given by the speciation diagrams and polarization curves must be considered together. Additionally, electrodeposition of Pb–Co films was achieved without complexing agent and using the three complexing agents. Morphological and chemical properties of these coatings are shown and discussed in terms of the electrochemical functioning of each system. Finally, the electrocatalytic ability of the Pb–Co films was investigated by means of polarization curves.

Influence of support electrolytic in the electrodeposition of Cu[sbnd]Ga[sbnd]Se thin films

CuGaSe2 is an important thin film electronic material that possesses several attributes that make it appealing for solar energy conversion. Due to its properties it can be incorporated in to various devices, among the greatest highlights are photovoltaic cells, as well as its potential use as photocathodes for hydrogen production, via the photoelectrolysis. There are several methods of its preparation, most notably electrodeposition that has the potential for large areas and high volumes. Electrodeposition of ternary and/or quaternary semiconductors generally proceeds via the formation of a binary, which is subsequently reacted to form the ternary compound. Several conditions must be controlled to form binary compounds that include the use of complexing agents, buffers, temperature, etc. In this paper, we discuss the effect of anion composition in the electrolytic bath and the type of lithium salts, in order to manipulate the atomic concentration of CuGaSe2 during the electrodeposition of thin films, yielding copper-rich, gallium-rich or stoichiometric thin films. We also present the results of a study on the morphology and structure obtained using two types of substrates both before and after performing a heat treatment.

Electrodeposition and characterization of as-deposited and annealed CdTe thin films

Thin films of CdTe semiconductor materials were grown on fluorine doped tin oxide (FTO) conducting glass substrates using the technique of electrodeposition. CdSO 4 at high concentrations and CdCl 2 , TeO 2 at low concentrations were used as precursor salts for electrodeposition. The range of deposition potentials was estimated using cyclic voltammetric measurements. The electrical, optical, structural and morphological characteristics of as-deposited and annealed CdTe thin films were characterized using photo-electrochemical (PEC) cell studies, UV-Vis spectrophotometry, X-ray diffraction (XRD) and scanning electron microscopy (SEM). These particular samples were converted from n-type into p-type after heat treatment. UV-Vis spectrometric measurements for CdTe layers indicated that, the energy band gaps of 1.45±0.02 eV for both as-deposited and annealed samples which exhibited the required optical property for fabricating CdS/CdTe solar cells. Little increase in (220) and (311) peaks of XRD spectra were observed for annealed layers compared to the as-deposited material. However, annealing exhibited a small reduction of cubic phase preferential orientation (111). The optical transmission for both as-deposited and annealed CdTe samples were about 60% for wavelengths longer than about 850 nm.

Electrodeposition of Cobalt Selenide Thin Films Using Combined Voltammetry and Electrochemical Quartz Crystal Microgravimetry

Electrodeposition and composition of CoSe thin films have been studied using electrochemical quartz crystal microgravimetry and stripping voltammetry. CoSe thin films were synthesized using 0.1 M KNO3 solution containing SeO2 and Co(NO3)2 at room temperature. During the electrodeposition, selenium was electrodeposited first, followed by the induced under potential deposition of cobalt to result in CoSe films. Photocurrent transients proved that as synthesized Se and CoSe are p-type semiconductors and their band gaps have been determined with reflectance spectrometry. Deposition mechanism and effect of electrolyte composition on the film composition were studied in detail using electrolyte containing different ratio. Composition of CoSe thins films has been determined by combining EQCM and stripping voltammetry. First, free selenium in the electrodeposited film was reduced to soluble Se2- at –0.8 V in 0.1 M Na2SO4 solution and frequency change was used to determine the content of free selenium. The film was again subjected to –1.5 V in the same blank electrolyte to reduce CoSe to Co+Se2- and accompanied frequency change was used to determine selenium in CoSe based on the 1:1 stoichiometry. Finally, the content of free cobalt in the electrodeposited film was determined from the frequency change during the oxidation of Co to Co2+ and difference between total cobalt and cobalt in CoSe thin film. Compositional analysis indicated that film composition is sensitive to electrodeposition potential as well as composition of electrolyte.

Electrodeposition of Cumn from a Deep Eutectic Electrolyte

We demonstrate our recent progress in conducting electrodeposition of CuMn thin film using a deep eutectic solvent, which consists of CHCl and ethyl glycol. The sources for Cu ions and Mn ions are C10H14CuO4 and MnCl2, respectively. Plating methods such as potentiostatic, galvanostatic, and current pulsing have been explored with relevant electrochemical parameters optimized and discussed. We determine that the current pulsing route enables the formation of CuMn thin film with desirable Mn amount. Material characterizations including Scanning Electron Microscopy, X-ray diffraction, X-ray Photoelectron Spectroscopy, and X-ray Absorption Microscopy have been carried out. Our results indicate that Mn exists in both metallic form and oxide, and after heat treatment, precipitates with excess Mn are found on the surface. In addition, the conductivity of deep eutectic electrolyte is greatly affected by the ambient moisture and consequently, the plating process is kept in a glovebox to minimize unnecessary interference.

The Effect of Bath Condition on the Composition of Si Thin Films Electrodeposited in Non-Aqueous Solvents

Si thin films are attracted as materials for ultra-large-scale solar cell systems at relatively low cost. Electrodeposition is expected as one fabrication method of Si thin films due to its advantages such as relatively simplicity process, precision control of nanostructure and continuous deposition in large area. Si thin films have been electrodeposited in non-aqueous solvents owing to their large electrochemical windows which allows for the study of Si electrodeposition [1-3]. Among various non-aqueous solvents, organic solvents and ionic liquids, which can be used under low temperature, have been used as electrolytes for the electrodeposition of Si thin films in our laboratory. We have previously succeeded to electrodeposit Si thin films in organic solvents and ionic liquids [4-6]. However, there is a problem for applications to solar cells that some impurities (mainly carbon and oxygen) are incorporated in thin films. We have reported the carbon content can be reduced by annealing treatment [7]. On the other hand, the decrease of oxygen content is still required. Thus, we evaluate the composition of Si thin films electrodeposited in an organic solvent and an ionic liquid without oxygen atoms in order to analysis the effect of bath conditions on the composition of thin films (especially, where the oxygen incorporated in Si thin films comes from). Si thin films were electrodeposited with 3 electrode cell (W.E. : Au, R.E. : Ag/Ag+, C.E. : Pt) in acetonitrile, 0.3 M tetrabutylammonium chloride and 0.5 M SiCl4 was used as an organic solvent, and 1-butyl-3-methylimidazolium hexafluorophosphate and 0.5 M SiCl4 as an ionic liquid. The composition of Si thin films were evaluated by X-ray photoelectron spectroscopy. As a result, the oxygen content in Si thin films were decreased by using the solvents without oxygen atoms in both organic solvent and ionic liquid cases. This results suggest that the reason the oxygen inclusion is derived from the incorporation of solvents themselves in films during electrodeposition, and propose us the way to obtain films with low impurities. In addition, the rotating disk electrode was used in the organic solvent case in order to promote the convection. The usage of this rotating disk electrode showed the decrease of impurities in Si thin films. Therefore, it is indicated that the stable supply of SiCl4 to the electrode surface is important factor to obtain films with low impurities. This study reveals that bath condition significantly affects to the composition of Si thin films, and could help us to fabricate films for applications to solar cells. This study was financially supported in part by the Japan Science and Technology Agency (JST) CREST program, and Y. T. acknowledges the Leading Graduate Program in Science and Engineering, Waseda University, from MEXT, Japan. [1] S. Zein El Abedin, N. Borrissenko, F. Endres, Electrochem. Comm., 6 (2004) 510. [2] T. Munisamy, A. J. Bard, Electrochim. Acta, 55 (2010) 3797. [3] M. Bechelany, J. Elias, P. Brodard, J. Michler, L. Philippe, Thin Solid Films 520 (2012) 1895. [4] Y. Nishimura and Y. Fukunaka, Electrochim. Acta, 53 (2007) 111. [5] T. Homma, J. Komadina, Y. Nakano, T. Ouchi, T. Akiyoshi, Y. Ishibashi, Y. Nishimura, T. Nishida, and Y. Fukunaka, Electrochem. Soc. Trans., 41 (2012) 9. [6] J. Komadina, T. Akiyoshi, Y. Ishibashi, Y. Fukunaka, T. Homma, Electrochim. Acta, 100 (2013) 236. [7] Y. Tsuyuki, A. Pham, J. Komadina, Y. Fukunaka, T. Homma, Electrochim. Acta, 183 (2015) 49.

Exploring Different Concepts for 2D Cu Growth on Ru(0001) Assisted By Pb UPD Monolayer

The properties of heteroepitaxial thin films are much dependent on the method used for their deposition. The electrodeposition represents the ambient temperature process offering the opportunity to grow many heteroepitaxial metal overlayers while preserving the integrity of their interface. In recent years, a significant progress has been made in understanding the kinetic aspects controlling the growth modes [[i],[ii],[iii]]. The improved understanding has led to various discoveries in which the growth kinetics was manipulated to enhance the evolution of atomically flat epitaxial overlayers [[iv],[v],[vi]]. Exploiting some of these results has led to development of several new methods and protocols for electrodeposition of heteroepitaxial thin films assisted by UPD monolayer serving as a mediator, surfactant or sacrificial template. [[vii],[viii],[ix],[x]]. In this talk we will briefly review the progress in the electrochemical thin film growth assisted by UPD ML. Our focus is examining the epitaxial growth of Cu on Ru(0001) assisted by Pb UPD ML. Cu and Ru represent the overlayer/substrate system which has significant epitaxial strain (-5.5%). This fact together with room temperature growth conditions favor a 3D growth. However, as we will show in our talk (Figure 1), with convenient use of Pb UPD ML serving as surfactant, or mediator, a 2D growth of Cu on Ru is induced. Characterization of 2D Cu overlayers indicates that their quality is comparable to MBE grown films which qualifies our approach as relevant for many high-tech applications. Our results also re-confirm the fact that Pb UPD ML-assisted electrochemical growth could be used to produce smooth 2D films of various metal overlayers even in situations where both thermodynamics and kinetics conditions do not favor positive outcome. The authors acknowledge the support from NSF Chemistry division under the contract # 0955922. [i] Physics of Crystal Growth, A. Pipinelli and J. Villain, University Press, Cambridge, UK (1998). [ii] J. Tersoff, A.W. Denier van der Gon, and R.M. Tromp, Phys. Rev. Lett. 72, 266 (1994). [iii] G. Rosenfield, B. Polesma and G. Comsa in Chemical Physics of Solid Surfaces ed. D. A. King and D. P. Woodruff, vol. 8, Elsevier, New York (1997), p. 70. [iv] G. Rosenfeld, R. Servaty, C. Teichert, B. Poeselma and G. Comsa, Phys. Rev. Lett., 71, 895 (1993). [v] H. A. van der Vegt, H.M. van Pinxteren, M. Lohmeier, E. Vlieg and J.M.C. Thornton, Phys. Rev. Lett. 68, 3335 (1992). [vi] H. A. van der Vegt, H.M. van Pinxteren, M. Lohmeier, E. Vlieg and J.M.C. Thornton, Phys. Rev. Lett. 68, 3335 (1992). [vii] K. Sieradzki, S.R. Brankovic and N. Dimitrov, Science, 284, 138 (1999). [viii] S. R. Brankovic, Electrochemical Mediated Growth, PhD Thesis, Arizona State University, Tempe (1999) [ix] S.R. Brankovic, N. Dimitrov and K. Sieradzki, Electrochem.Solid-State Lett., 2, 443 (1999). [x] S.R. Brankovic, J.X. Wang and R. R. Adzic, Surf. Sci., 474, L173 (2001). Figure 1

Interconnected Ni Nanowire Scaffolds for Fast-Charging 3D Thin-Film Lithium-Ion Batteries

The growing market of small consumer electronics, such as cell phones, smartwatches or electronic eyewear requires development of small power sources that allow for both satisfactory usage time and fast charging. Lithium-ion batteries (LIBs) are currently the systems of choice thanks to their high energy and power density. However, downscalling these batteries for small device applications still possess a big challenge. Due to electronically and ionically resistive nature of the active materials, mini-LIBs are currently made only in thin film technology, thus the total output energy and power density are still far too low for consumer device applications. Also, the manufacturing of thin film batteries requires sophisticated PVD/CVD deposition techniques. To overcome these issues, 3D architecturing of the current collector can be employed [1, 2]. This can provide a system where very thin active materials are stacked over enormously large surface area of a 3D current collector to yield a cell with both high power density (due to reduced materials thickness) and high energy density (thanks to large total volume of the active materials). Herein, we report reproducible fabrication of 3D-interconnected nickel nanowires (Fig. 1) prepared by electrodeposition of nickel into anodized aluminum oxide (AAO) template. The inter-branching of the wires provides rigidity of the structure, together with increase of the surface area of the current collector. The total surface area enhancement of the electrode was characterized by electrochemical passivation of the nickel nanowires and reached values up to 60x for 3 μm-long 3D nanoscaffolds. Additionally, we present results of electrodeposition of thin films of electrolytic manganese dioxide (EMD) on our 3D current collector and their activity as battery electrodes. This shows the potential of the 3D Ni-meshes for cheap fabrication of high power density electrodes for thin-film lithium-ion batteries. J. F. M. Oudenhoven, L. Bagetto, P. H. L. Notten, Adv. Energy Mater., 2011, 1, p. 10-33.J.Vanpaemel, A. M. Abd-Elnaiem, S. De Gendt, P. Vereecken, J. Phys. Chem. C, 2015, 119 (4), pp 2105-2112 Figure 1

Electrodeposition of Lithium Anode Thin Films and Its Application in All-Solid-State Microbatteries

Thin film all-solid-state secondary microbatteries are extensively studied since the 1990’s [1-3]. These systems present specific features such as reduced surface, high thermal resistance, excellent cycle life, absence of liquid electrolyte, etc. that make them the most suitable energy sources for some emerging applications (real time clock, medical implants, secured smart cards, etc.). All-solid-state microbatteries are realized by successive deposition of thin films with a total thickness of less than 20 µm. The corresponding manufacturing steps are mainly carried out using physical vapor deposition processes such as thermal evaporation or sputtering, which are commonly used in the microelectronics industry. Each deposited layer is patterned either with shadow mask or photo-lithography step. Shadow masking process involves restrictive steps such as mask alignment and cleaning. Moreover, standard photolithography processes, commonly used in the microelectronics industry, are actually difficult to adapt to microbattery systems considering the high reactivity of active materials, mainly lithium metal and lithiated compounds like LiPON. The use of such techniques, for deposition as well as patterning steps, involves sophisticated equipment leading to high production and maintenance costs. Furthermore, deposition rates of each processing step remains rather low (~ 10 nm mn-1 for sputtering techniques). In this study, to increase throughput and limit production costs, Lithium anode thin films are deposited via an easy electrochemical route [4-5] using standard carbonate based electrolyte with LiPF6 salt. Deposited films exhibit self-aligned nanorods structure without any dendritic growth. The electrochemical performance of such lithium electrodes is evaluated in coin cell configuration versus silicon thin films and no obvious difference in behavior is observed between electrodeposited lithium thin films and bulk lithium metal foils. The process is then used to manufacture all-solid-state thin film battery stacks. The lithium anode electrodeposition on non-conductive LiPON layer is possible through the use of very thin Cu layer (Fig1). The all solid state micro-battery stack is then composed of a silicon cathode, LiPON as solid electrolyte, copper as conductive layer for the electrodeposition process and electrodeposited lithium as anode material (Fig2). Finally, the electrochemical performance (cycle life, specific capacity and curve shape (Fig3)) is close to those obtained with standard evaporated lithium (without Cu layer). This new lithium film deposition technique is suitable for 3D textured or high roughness substrates and limited to electronic conductive surfaces. In the end, this enables a direct patterning of the lithium anode layer. Therefore, considering that all other microbattery materials can be structured by photolithography, the Li electrodeposition could avoid using shadow masking technique during the all-solid state microbatteries manufacturing process. The authors thank ST-Microelectronics and the French Directorate General for Enterprise (DGE) for financial support through the Tours2015 project. [1] J.B. Bates, N.J. Dudney, D.C. Lubben, G.R. Gruzalski, B.S. Kwak, X. Yu, R.A. Zuhr, J. Power Sources 1995, 54,58-62. [2] J.B. Bates, N.J. Dudney, B. Neudecker, A. Ueda, C.D. Evans, Solid State Ionics 2000, 135,33-45. [3] B. Fleutot, B. Pecquenard, F. Le Cras, B. Delis, H. Martinez, L. Dupont, D. Guy-Bouyssou, J. Power Sources 2011, 196,10289-10296. [4] X. Yang, Z. Wen, X. Zhu, S. Huang, Solid State Ionics 2005, 176,1051-1055. [5] J. Qian, W. Xu, P. Bhattacharya, M. Engelhard, W.A. Henderson, Y. Zhang, J.-G. Zhang, Nano Energy 2015, 15,135-144. Figure 1

Nanometer-Thick Gold on Silicon as a Proxy for Single-Crystal Gold for the Electrodeposition of Epitaxial Cuprous Oxide Thin Films.

Single-crystal Au is an excellent substrate for electrochemical epitaxial growth due to its chemical inertness, but the high cost of bulk Au single crystals prohibits their use in practical applications. Here, we show that ultrathin epitaxial films of Au electrodeposited onto Si(111), Si(100), and Si(110) wafers can serve as an inexpensive proxy for bulk single-crystal Au for the deposition of epitaxial films of cuprous oxide (Cu2O). The Au films range in thickness from 7.7 nm for a film deposited for 5 min to 28.3 nm for a film deposited for 30 min. The film thicknesses are measured by low-angle X-ray reflectivity and X-ray Laue oscillations. High-resolution TEM shows that there is not an interfacial SiOx layer between the Si and Au. The Au films deposited on the Si(111) substrates are smoother and have lower mosaic spread than those deposited onto Si(100) and Si(110). The mosaic spread of the Au(111) layer on Si(111) is only 0.15° for a 28.3 nm thick film. Au films deposited onto degenerate Si(111) exhibit ohmic behavior, whereas Au films deposited onto n-type Si(111) with a resistivity of 1.15 Ω·cm are rectifying with a barrier height of 0.85 eV. The Au and the Cu2O follow the out-of-plane and in-plane orientations of the Si substrates, as determined by X-ray pole figures. The Au and Cu2O films deposited on Si(100) and Si(110) are both twinned. The films grown on Si(100) have twins with a [221] orientation, and the films grown on Si(110) have twins with a [411] orientation. An interface model is proposed for all Si orientations, in which the -24.9% mismatch for the Au/Si system is reduced to only +0.13% by a coincident site lattice in which 4 unit meshes of Au coincide with 3 unit meshes of Si. Although this study only considers the deposition of epitaxial Cu2O films on electrodeposited Au/Si, the thin Au films should serve as high-quality substrates for the deposition of a wide variety of epitaxial materials.

Efficient electrochemical treatment based on electrodeposited thin films of birnessite for mineralisation of AMPA (aminomethylphosphonic acid) in very soft conditions

The presence of AMPA in environment becomes today a real problem due to its persistence, its toxicity, and its multiple origins (main metabolite of glyphosate, the pesticide the most used in the world; degradation product of personal care and industrial products). This paper reports the development of a simple, effective, cheap and easy electrochemical treatment, for mineralising AMPA under very soft conditions: at room temperature, at free pH, and in a classical open electrochemical cell. The electrode material used is an electrodeposited thin film of birnessite, a non-toxic material, synthesised in very soft conditions. The original idea is to couple the spontaneous oxidative properties of birnessite to an electrochemical oxidation treatment in the aim to increase its reactivity towards this pollutant. Very good mineralisation rates and capacity (≈0.115g AMPA mineralized by gramme of birnessite) were obtained with very low energy supplies (Q≈3C). Some tests performed with concentrated glyphosate solutions, one of its main parents, give also good results allowing us to envisage the development of an easy method of wastewater treatments at very low costs in complement of classical methods and/or directly at the source of pollution.

One-step electrodeposition for targeted off-stoichiometry Cu2ZnSnS4 thin films

Cu2ZnSnS4 (CZTS) is a promising quaternary compound suitable for absorber layer of thin film solar cells. The precise control of the atomic ratio of the films are difficult for the electrodeposition of CZTS thin films. Here, we reported targeted off-stoichiometry CZTS thin films synthesized by one-step electrodeposition. We obtained Cu-poor thin films and the chemical composition of the as-deposited thin films were tailored to targeted off-stoichiometry. Based on the different kinetics of the metallic ion reduction, we successfully controlled the chemical composition by varying deposition time. After annealing, pure kesterite structure was obtained and the electronic interactions between Cu and Sn was verified in the films, which contributes to high carrier mobility. The band gap of the thin films were in the range of 1.43–1.52eV, which is suitable for absorber layers of thin film solar cells. The carrier mobility reached a value of 28.20cm2/Vs with carrier concentration of 2.09×1018cm−3 when Cu/(Zn+Sn) and Zn/Sn ratios were 0.97 and 1.13, respectively. This work paves a way for synthesizing targeted off-stoichiometry compounds by controlling kinetics and reaction time in large scale.

Potentiostatic electrodeposition of nanostructured NiO thin films for their application as electrocatalyst

We report the synthesis of nanostructured nickel oxide (NiO) films, and their implementation as photocathodes in photoelectrochemical (PEC) cells for hydrogen generation by water splitting. NiO nanograins were prepared by electrodeposition of nickel from complexing glycinate solution at different pH from 2 to 13, followed by annealing at 400°C. The characterization of NiO films was carried out by XRD, SEM, UV–vis, PL and electrochemical techniques. XRD study showed that NiO with cubic structure was obtained for all films. SEM micrographs showed a spherical-granular structure for NiO films with a grain size between 400 and 125nm. The measurements carried out on PEC cell with NiO as photocathodes, under simulated solar irradiation, demonstrated a significant increase of cathodic photocurrent as the pH of electrodeposition solution was increased. Analysis of Mott-Schottky plots for each NiO film showed a remarkable increment of the charge carrier density as the grain size was decreasing.