bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Epitaxial Lift-Off of Flexible and Transparent Single-Crystal Gold Foils from Silicon Wafers
Authors: Switzer Jay A.
Published: February 2020

Single-crystal silicon is the industry standard for electronic devices because of its high crystalline order and abundance. However, the brittle nature of bulk silicon precludes its use in flexible electronics. Here, we show a simple and inexpensive procedure for epitaxial lift-off of wafer-size flexible and transparent foils of single-crystal Au using Si(111) as a template. Lateral electrochemical undergrowth of a sacrificial SiOx layer was achieved by photoelectrochemically oxidizing n-Si(111) under light irradiation. The processing scheme is shown in Fig. 1. Cu2O as an inorganic semiconductor was epitaxially electrodeposited onto the Au foils, which showed a more ideal diode quality factor of 1.6 (where n=1 is ideal) than the value of 3.1 observed for a polycrystalline deposit. ZnO nanowires electrodeposited epitaxially on a Au foil showed flexibility with the nanowires intact up to 500 bending cycles. A 28 nm Au foil with a sheet resistance of 7 Ω.sq-1 showed only a 4% increase in resistance after 4000 bending cycles. A flexible organic light-emitting diode based on tris(bipyridyl)ruthenium(II) was spin-coated on a foil to exploit the transmittance and flexibility of the gold foil. The simple epitaxial lift-off procedure produces single-crystal Au foils that offer the order of traditional semiconductors such as Si wafers without the constraint of a rigid substrate.

Reference

[1] N. K. Mahenderkar, Q. Chen, Y.–C. Liu, A. R. Duchild, S. Hofheins, E. Chason, and J. A. Switzer, “Epitaxial lift-off of electrodeposited single-crystal gold foils for flexible electronics,” Science
355, 1203 (2017).

Fig. 1. Schematic for epitaxial lift-off of single-crystal Au foils [1].

Figure 1
Tuning Electrodeposition Conditions Towards the Formation of Smooth Bi2Se3 Thin Films
Authors: Souza Paloma Boeck , Tumelero Milton André , Zangari Giovanni , Pasa André Avelino
Published: February 2020

Bismuth selenide (Bi2Se3) is a semiconductor presenting two distinct crystalline phases, one with rhombohedral structure (R-3M), and another, metastable, with orthorhombic phase (Pnma). Each phase has distinct band gap and interesting optical, thermoelectric and topological electronic properties. Thin films of thicknesses up to 1.5 μm were grown by electrodeposition under constant potential onto silicon (100) substrate. It is shown that under an optimum set of deposition parameters, simultaneous heating and electrolyte stirring, very smooth and thick films can be obtained. Morphological characterization evidences the formation of compact, uniform and smooth layers, attributed to the growth of very small grains of ~50 nm. Structural characterization of the samples indicates a majority of a metastable orthorhombic phase with traces of a rhombohedral phase. The films grow initially with a rhombohedral crystalline structure, which progressively changes to orthorhombic, likely due to the accumulation of internal stresses and successive stress relaxation. In addition, a full recrystallization to the rhombohedral structure can be achieved by using short time and low temperature thermal treatments. These results show the possibility to grow smooth samples and also to control the crystalline structure of Bi2Se3. This is of interest since both phases present different but complementary properties, and each one or the combination of the two may be successfully exploited to the construction of low cost, efficient novel devices based on thermoelectric, optical or topological insulator technologies.
In-Situ Measurements of Stress during Electrodeposition of Copper Nanofilms: Effects of Deposition Rate and Grain Size
Authors: Buckley D. Noel , Murphy Joe A. , Lenihan Catherine , Chason Eric , Lynch Robert P.
Published: February 2020

Thin metal films deposited on a substrate are usually in a state of stress and this has been the subject of extensive experimental investigation and theoretical analysis. [1-4] Various studies of the stress generated during the electrodeposition and aging of copper films have been reported.

In this paper we report results of in situ stress monitoring during deposition of copper nanofilms from acidic CuSO4 electrolytes. Stress was monitored over a larger range of growth rates from 0.22 nm s-1 to 6.9 nm s-1 during deposition from additive-free electrolyte. At low growth rates, steady state stress was compressive. As growth rate was increased, the stress became less compressive and eventually became tensile. Crossover from compressive to tensile stress occurred at a growth rate of ~1 nm s-1. Both in-situ AFM imaging during deposition and ex-situ SEM imaging were used to characterise the evolution of grain size. In general, grain size increased with continued deposition but eventually reached a constant value.

Simulations based on a kinetic model [3] gave an excellent fit of our experimental stress measurements in the region of constant grain size (~870 nm). In the region of variable grain size, a fit of the model to the experimental data gave a grain size that is in good agreement with the average (520 nm) obtained from SEM and AFM.

The observed behaviour supports Chason’s model [3] of stress development in thin films. According to that model, stress originates primarily from effects at grain boundaries. As grain boundaries form, tensile stress tends to develop because of a so-called “zipping” effect whereby the surfaces of adjacent grains near the film surface tend to attract once the separating distance becomes small. When the attraction between adjacent grains becomes strong enough, they “zip” together, closing the gap between them and creating tensile stress as the material stretches slightly to fill the gap. Similar effects occur near the film surface as existing grains continue to grow: when the atoms at the edges of terraces on two adjacent grains get sufficiently close to each other they bond to each other even if that bond causes stress in the layer. This tensile stress can be relaxed or made compressive by the insertion of atoms into the grain boundary by diffusion from the surface. Our experimental results will be discussed in detail in terms of this model.

References

O.E. Kongstein, U. Bertoci, G.R. Stafford, J. Electrochem. Soc.
152, C116 (2005)

S. Ahmed, T.T. Ahmed, M. O'Grady, S. Nakahara, D.N. Buckley, J. Applied Physics
103, 073506 (2008)

E. Chason, Thin Solid Films
526, 1 (2012)

E. Chason, A. Engwall, F. Pei, M. Lafouresse, U. Bertocci, G. Stafford, J.A. Murphy, C. Lenihan, D.N. Buckley,J. Electrochem. Soc.
160, D3285 (2013)

Figure 1
Two-Dimensional Semiconductors Thin Films of MoS2 and MoSe2 on Ag(111)
Authors: Salvietti Emanuele , Vizza Martina , Giaccherini Andrea , Passaponti Maurizio , Piciollo Emanuele , Di Benedetto Francesco , Cavallini Massimiliano , Innocenti Massimo
Published: February 2020

In the recent years, technological development in the fields spanning from nanoelectronics to new solar energy materials, requires highly controlled nanostructured surfaces, ultra-thin films and 2D structured materials.

The Electrochemical Atomic Layer Deposition (E-ALD) is one of these techniques that allows us to produce thin films of semiconductor. Exploiting Surface Limited Reactions (SLR), it enables the deposition of highly ordered ultra-thin films from diluted aqueous solutions and at room temperature and pressure.

Underpotential deposition (UPD) is a type of electrochemical SLR, where an atomic layer of a first element is deposited on a second, at a potential prior to (under) that needed to deposit the first element on itself, so that the resulting deposit is generally limited to an atomic layer.

It occurs when the depositing element is able to somehow interact with the substrate, so that the deposition of the layer in direct contact with the substrate occurs at a potential preceding bulk deposition, that is, the deposition of the element on itself.

MoS2 and MoSe2 are important transition metal dichalcogenides (TMDs). E-ALD method was used to obtain semiconductor compounds in the form of thin films. UPD anodic electrodeposition of Na2S and Na2SeO3 on crystalline Ag[111] electrode are well-known. The research move to discover the optimal conditions to deposit Mo on Ag/S and on Ag/Se from a solution of MoO4
2- in alkaline buffer. This study has been carried by means of voltammetric techniques, XPS and AFM characterizations of the deposit.
In-Situ observation of Cu Electrodeposition and Dissolution Behavior By Video-AFM
Authors: Yoshioka Taiki , Matsushima Hisayoshi , Ueda Mikito
Published: February 2020

1. Introduction

 Advanced nanotechnology applications are requires copper plating and epitaxial control by electrochemical method, which is used for various electronic devices such as a micro machine technology (MEMS). To control the surface structure of the plating film with high precision at the nanometer size, it is indispensable to clarify the mechanism of electrodeposition. However, since the electrochemical reaction process in nucleation and growth occurs rapidly in a small area, it is extremely difficult to capture the dynamic behavior at the nanoscale. In this study, we investigate the nucleation and growth process at the initial stage of copper electrodeposition by using Video-AFM.

2. Experimental

A three-electrode electrochemical AFM cell was used for in-situ observation. In the cell, the working electrode was single crystal Au(100) substrate (φ= 3 mm). The reference electrode was a copper wire and the counter electrode was a platinum wire. Potentiostatic electrodeposition was carried out in an aqueous electrolyte containing 3 mM CuSO4 and 50 mM H2SO4 at room temperature. The Video-AFM measurement was performed during potentiostatic electrodeposition. The image area (500×375 nm2) was recorded at 2 flame s-
1

3. Results and discussion

When the experiment was carried out at -0.09 V, the initial stage of the deposition on Au substrate was shown in Fig.1(a)~(d). Before electrodeposition, a smooth substrate without any irregularities was observed. Immediately after the start of electrodeposition, copper deposited with about 100 nm in x-axis direction instantaneously (Fig.1 (a)), and it was confirmed that growth of the deposited copper in the planar direction (Fig.1 (b) ~ (d)). From these images, the local deposition rate in the planar direction was calculated as 45 nm s-
1. From the height profile, the thickness of the deposit was about 1 nm, which was corresponding to 4 or 5 atomic layers.

Figure 1
Au-Pd-Pt Multilayer Catalyst for Miniature Fuel Cells
Authors: Shirai Ryo , Vasiljevic Natasa , Hayase Masanori
Published: February 2020

We have developed miniature fuel cells with monolithically fabricated Si electrodes. In the fuel cells, two Si electrodes with porous Pt catalyst layer, which Pt usage was 3.6mg/cm2, were hot-pressed onto either side of a PEM (polymer electrolyte membrane), and the prototype fuel cells showed promising performances of over 500mW/cm2 output at 313K with H2-O2. However, recent improvements of Li-ion battery are lowering expectation to the miniature fuel cells. The advantage of the fuel cell, i.e. clean and efficient energy source, should be strengthened.

Bio-mass is an ultimate energy source. Hydrogen can be produced by gasification of the bio-mass in reducing environment, but high CO concentration in the bio-mass derived hydrogen is inevitable. Catalyst poisoning by CO is problematic. We found that our Pd-Pt catalyst obtained by using UPD-SLRR had promising feature. Though the catalyst layer used only 6μg/cm2 of Pt, high tolerance to CO was observed. But Pd and Pt are rare metals, and both amounts should be minimized. In this study, a novel Au-Pd-Pt multilayer catalyst is proposed. Though Au is also a precious metal, reserve of Au is much larger than Pd and Pt, and porous Au can be formed on a Si substrate by similar process to porous Pt.

There is no clear evidence, but it is assumed that high CO tolerance of the Pd-Pt catalyst is realized with sub-monolayer Pt on Pd. Hydrogen absorption or stress near the interface between Pd and Pt are sensitive to the number of atomic layer of Pd, and fine control of Pd and Pt deposition on Au is crucial. In our previous study, sub-monolayer Pt was deposited with Cu-UPD, but hydrogen also absorbs on some metal surfaces and form atomic monolayer at slightly under the equilibrium potential. The H-UPD-SLRR can be performed just in an acidic plating bath containing Pd2+ or Pt4+. There is no need to replace the plating bath, and repetition of the atomic layer deposition process will be easy. In this study, basic fabrication strategy of the Au-Pd-Pt multilayer catalyst using H-UPD-SLRR process was examined using Au wire. Preliminary results of cyclic voltammetry suggested that Pd and Pt were successfully deposited on Au wire, and only one Pt deposition cycle on the Au wire with Pd, deposited by several UPD-SLRR cycles, showed large hysteresis loop in the CV, which related to catalytic performance.
(Electrodeposition Division Research Award Address) Metal Deposition Assisted by UPD Monolayers-Fundamentals and Applications
Authors: Brankovic Stanko R
Published: February 2020

The improved understanding of nucleation and growth kinetics provided the base for design of new experimental approaches where the thin film growth was manipulated to enhance the evolution of atomically flat epitaxial overlayers. Following this progress, a new protocols for electrochemical thin film growth were developed which benefit from the Underpotentially Deposited Monolayers (UPD ML) serving as a surfactants (Surfactant Mediated Growth, SMG), mediators (Defect Mediated Growth, DMG) or sacrificial materials (Deposition via Surface Limited Redox Replacement, SLRR) in electrodeposition process of thin films. In these examples, the essential step that results in desired 2D growth mode is achieved by precise control of the electrode potential, electrodeposition sequence and/or solution chemistry which enable particular action/benefit of the UPD ML to be fully exploited in the growth process.

In the first part of the talk we will briefly review fundamentals of the electrochemical thin film growth assisted by UPD ML. Our results and discussion are focused on examining the extendibility of SMG, DMG and SLRR approach for thin film growth in technologically relevant system such as Cu/Ru(hklm). The Cu/Ru(hklm) represents 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 it will be shown, with convenient use of UPD ML serving as surfactant, or mediator, or sacrificial material a 2D growth of Cu on Ru can be achieved readily.

In the second part of the talk we will demonstrate that UPD-like ML can be deposited on different substrates using an electroless (e-less) approach. The example of improved morphology and magnetic properties of e-lessly deposited Co overlayers on Cu assisted by e-lessly deposited Pb ML serving as surfactant are analyzed. The phenomenon of e-less UPD-like ML deposition as a prelude for e-less atomic layer epitaxial deposition (E-less ALD) will be discussed as well. We will show results demonstrating noble metal thin film growth on Cu and other substrates using e-lessly deposited Pb UPD-like ML serving as a reducing precursor in SLRR reaction with noble metal ions such as Pt, Pd, and Ru. In conclusion of the talk, (if time permitted), the results from exploratory research studying the benefit of UPD ML serving as a stress moderators in electrodeposition process of Pd thin films will be discussed.

The author acknowledges support from Lam Research Corporation and NSF Chemistry division under the contract # 0955922 and #1605331.
Manufacture of Copper Foils for the Current Collector of Lithium-Ion Batteries By Electrochemical Deposition
Authors: Lin Chun-Cheng , Hu Chi-Chang
Published: February 2020

Manufacture of copper foils by electrochemical deposition is a mature and indispensable technique in the modern industry, and one of the important products is the copper clad laminate for printed circuit board industry. In recent years, as the rapid increase in electric cars industry, the demand for Cu foils acting as the current collector of negative electrodes for lithium-ion batteries (LIBs) surges strikingly. Nonetheless, the method to produce Cu foils for LIBs could not be conducted by electrochemical deposition but by rolling, since the rolled copper foils provides a double side smooth surface, which is crucial to achieve good capacity retention rate of LIBs. Moreover, rolled copper foils possess excellent mechanical properties such as tensile strength to ensure the foils pass through the following roll-to-roll coating process without fracture. Unfortunately, rolled Cu foils are much costly in comparison with the electroplating, especially for thin foils since it require more times of rolling and annealing the copper ingot. Meanwhile, the surface roughness of electrodeposited Cu foils on both sides is distinctively different by the conventional electrolyte composition, which is known to deteriorate the capacity retention rate of LIBs. Consequently, we introduced several organic additives that had been applied in copper damascene plating into copper foils plating, and attempted to manufacture Cu foils with optimal quality that can meet the requirements to be adopted into LIBs. Unlike damascene process, the target of using additives is not to change the deposition rate of copper, but to modify the surface morphology and strengthen the structure of the deposited copper. In addition, the applied current density of Cu foil plating usually ranges from 500 to 1000 mA·cm-2, which is 20 times more than damascene plating. Correspondingly, the convection rate in the plating bath ought to be extremely high to make sure the limiting current density higher than the applied current density. Therefore, the electrochemical behavior of each additives has yet to be studied under such high current densities and strong flow-rate environments. Last but not least, the degradation rate of the organic additives may be much faster since the current density is much higher. To produce Cu foils with consistent quality, understanding the bath aging problem and the proper method to maintain the bath is very important. In this research, the effects of the selected additives on the structure and surface morphology of deposited copper, the electrochemical behavior of additives under high current density, and the full consideration to solve the bath aging issue will be presented. Ultimately, a proper solution to manufacture Cu foils for LIBs by electrochemical deposition will be proposed.
The Study of Complexed Copper(II) Ion and Its Application for Electroless Copper Deposition
Authors: Chang Hong-Ming , Dow Wei-Ping
Published: February 2020

Nowadays, sidewall metallization of microvias and through holes of a printed circuit board (PCB) after drilling and desmearing processes mainly utilizes palladium as a catalyst for electroless copper plating process. Although the palladium catalyst has been commonly used in PCB metallization, the palladium catalyst is expensive. In this work, we use complexed copper(II) ion to replace the palladium catalyst in order to greatly reduce the process cost and maintain the same metallization performance and reliability as that of palladium. The synthesis process of the complexed copper ion is simple and its cost is inexpensive compared to palladium. Particularly, they have no oxidation issue because they are not metallic copper nanoparticles but copper(II) ions. In this study, we utilized a PCB with through holes as a substrate. A conditioner with a quaternary ammonium group was employed to graft the complexed copper(II) ions onto the sidewalls of these through holes. Before electroless copper plating, the grafted copper(II) ions were chemically reduced to copper atoms, so that they can catalyze electroless copper deposition. The deposition performance of the electroless copper plating on the sidewall of a through hole catalyzed by the grafted copper catalyst were examined by backlight degree analysis using an optical microscope (OM) and surface morphology analysis using a scanning electron microscope (SEM). The thermal reliability of the electroless copper deposition catalyzed by the grafted copper catalyst was examined after copper electroplating using thermal shock in a tin bath at 288℃ for ten seconds and repeated it for 5 times. Results show that it can pass the thermal shock test.
Light Assisted Electrodeposition for Silicon Solar Cell Copper Metallization
Authors: Huang Qiang
Published: February 2020

Cu electroplating is of a great deal of interest for the metallization of silicon solar cells due to its comparable resistance with the current silver metallizaion, and its lower cost for both the material and the operation.[1,2] However, the notorious Cu diffusion into Si is of great concern to the devices performance degradation during the life cycle of the cells. Ni silicide and Ni metal layers have been recently reported as part of the integration scheme to enable the Cu metallizaion and greatly improved the solar cell reliability.[3,4] The formation of this Ni silicide and Ni stack structure is to provide a low-resistance contact between the silicon and metal grid, a good adhesion of metal grid, and a diffusion barrier for the Cu. Among them, the Ni silicide formation needs to be well controlled so that it is not too thick to shunt the solar cell.

This paper will present the development of light assisted plating processes for the formation of nickel silicide and copper grids on silicon solar cells, including beaker scale, bench top tool, and pilot tool processing[5,6,7]. The solar cell substrates for plating comprise ~ 60 ohm/sq emitter formed by POCl diffusion, PECVD SiN passivation layer, and evaporated Al back surface field. Electrodeposition of Ni and copper was studied on 4 cm x 4 cm solar cells in small scale studies and 6 in x 6 in cells on tools.

Figure 1 shows the absorption spectra of different electrolytes for deposition and the relation between the applied potential and the light intensity at different constant current densities. Nickel solution has a strong absorption at wavelength between 350 to 450 nm and between 600 to 800 nm. Two regions of operation were clearly observed with a threshold light intensity when a high intensity wide spectrum halogen light source is used for illumination during electroplating. At high illumination, when enough carriers were generated by the light, the plating occurs at the forward bias mode of the diode. As the light intensity decreases below a threshold value, the potential increases significantly and stays at a high value indicating the diode operates at reverse bias mode. The threshold light intensity is dependent on the illumination energy spectrum, solution absorbance, anode shadowing and applied current density. The learnings from beaker scale experiments were directly used to define the tool requirements and process specifications.

REFERENCES

D. A. Yates, US Patent 4,609,565 (1986).

K. Holdermann, US patent 5,543,333 (1996).

J Bartsch, A Mondon, K Bayer, C Schetter, M Horteis, and S W Glunz, J. Electrochem. Soc., 157, H942 (2010).

J Bartsch, A Mondon, C Schetter, M Horteis, S W Glunz, IEEE 35th PVSC, Honolulu HI (2010).

Q Huang, S S Papa Rao, K. Fisher, ECS J. Solid State Sci. Technol., 4, Q75 (2015).

Q Huang, ECS J. Solid State Sci. Technol., 5, P51 (2016).

Q Huang, K B Reuter, Y Zhu, V R Deline, ECS J. Solid State Sci. Technol., 5, Q24 (2016).

Figure 1
(Invited) Electrodeposition of Functional Nanomaterials from Weakly Coordinating Solvents
Authors: Bartlett Philip Nigel
Published: February 2020

Electrodeposition is already well established as a key process step in the fabrication of electronic devices in microchip manufacture via the double Damascene process (1) and in through template plating in the manufacture of hard disk read write heads (2). Electrodeposition has great potential in the patterned deposition of materials for a range of other applications, such as solid state memory, thermoelectrics or infrared detection. In addition to providing a relatively green and scalable method for the preparation of thin film materials, electrodeposition brings significant advantages in the filling of high aspect ratio nanostructures compared to more conventional preparation processes, such as PVD or CVD, which make it especially appealing for the fabrication of sub 20 nm structures.

The p-block elements and their compounds and alloys are important materials for many electronic applications. Over the last 4 years we have developed an electrolyte system based on compatible tetrabutylammonium chlorometallate metal sources in non-aqueous electrolytes (3, 4) that allows the one-pot preparation of a wide range of functional materials, such as GeSbTe(5), CdHgTe, and BiTe, based on the p-block.

In this lecture I will discuss the electrodeposition of p-block elements from weakly coordinating solvents and present results for the electrodeposition and electrical characterization of GeSbTe solid state memory materials and CdHgTe infrared detector materials and contrast their properties to the properties of conventionally prepared materials.

This work is conducted as part of the ADEPT project funded by EPSRC (EP/N035437/1).

References

1. P. C. Andricacos, C. Uzoh, J. O. Dukovic, J. Horkans and H. Deligianni, IBM J. Res. Dev., 42, 567 (1998).

2. L. T. Romankiw and S. Krongel, “The Path from Invention to Product for the Magnetic Thin Film Head” in Electrochemical Engineering Across Scales: From Molecules to Processes, R. C. Alkire, P. N. Bartlett and J. Lipkowski (Eds), Wiley, Weinheim, 2015.

3. P. N. Bartlett, D. Cook, C. H. de Groot, A. L. Hector, R. M. Huang, A. Jolleys, G. P. Kissling, W. Levason, S. J. Pearce and G. Reid, RSC Adv., 3, 15645 (2013).

4. P. N. Bartlett, J. Burt, D. A. Cook, C. Y. Cummings, M. W. George, A. L. Hector, M. M. Hasan, J. Ke, W. Levason, D. Pugh, G. Reid, P. W. Richardson, D. C. Smith, J. Spencer, N. Suleiman and W. Zhang, Chem. Eur. J., 22, 302 (2016).

5. P. N. Bartlett, S. L. Benjamin, C. H. de Groot, A. L. Hector, R. M. Huang, A. Jolleys, G. P. Kissling, W. Levason, S. J. Pearce, G. Reid and Y. D. Wang, Mater. Horiz., 2, 420 (2015).
Electrodeposition of Aluminum and Aluminum-Ruthenium Films in Ionic Liquids
Authors: Ispas Adriana , Schlag Leslie , Böttcher Rene , Jacobs Heiko O. , Bund Andreas
Published: February 2020

Aluminum is one of materials often used in different technical applications due to its light weight and its good corrosion resistance. Its melting temperature is around 660°C, therefore, it can be successfully used for corrosion protection of different materials below this point. Intermetallic phases between Al-Ru are promising candidates for corrosion protection in aggressive media at temperatures above 660°C. Polycrystalline Al-Ru layers present an exceptionally high ductility at room temperature. All these physical, chemical and mechanical properties of Al and Al-Ru films make them interesting for a variety of applications.

One can obtain Al and Al-Ru films by sputtering or by sintering by powder metallurgy and casting, as well as by electrodeposition. Aqueous solutions cannot be used for electrodeposition of Al, therefore, ionic liquids (ILs) were chosen in this study as electrolytes.

The electrolyte used in our work for deposition of Al consisted of 1:2 molar ratio of 1-ethyl-3-methylimidazolium chloride, [EMIm]Cl, and AlCl3. As an alternative, 1-butyl-1-methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]amide, [BMP][TFSA], has also been investigated. RuCl3 and AlCl3 were two of the sources chosen for Al and Ru. Moreover, Ru particles produced by gas phase electrodeposition, were added to an Al electrolyte. The morphology and the composition of the deposited layers were investigated by SEM/EDX. The effect of the IL and of the precursor for Ru on the growth of the layers and on the properties of the deposited films will also be discussed.
All-Inorganic Nanocrystal Thin Films Fabricated By Low-Voltage Electrophoretic Deposition
Authors: Dillon Andrew D , Taheri Mohammad , Mengel Shawn , Dastidar Subham , Baxter Jason , Fafarman Aaron T
Published: February 2020

The solution processability of colloidal nanocrystals (NCs) offers prospective next-generation solar cells significantly reduced fabrication costs, yet methods for scalable deposition of conductive, well-adhered NC films have yet to be realized. Electrophoretic deposition (EPD), a low-waste, high-throughput technique used commercially in other fields, is proposed for depositing solution-processed absorbing layers for solar cells. Here we share methods for fabricating all-inorganic semiconductor-NC films through low-voltage EPD. Through light scattering, absorbance spectroscopy and electric measurements, the fundamental electrochemical reactions and transport processes that occur during EPD are studied. Special emphasis is applied to elucidate the requirements for low-voltage EPD of semiconductor NCs. Through insights gleaned from this study, choice of NC-ligand-solvent combinations and reactor design, film electronic properties and morphology improvements are realized. Low-voltage EPD is demonstrated using both continuous flow and batch reactors in this study.
(Invited) Problems and Solutions for Lithium Metal Rechargeable Batteries
Authors: Blomgren George E
Published: February 2020

Lithium metal rechargeable batteries were extensively examined from the 1960s until the discovery and development of the lithium ion battery in 19911. The earlier work was compromised by the lack of development of materials of adequate purity, particularly with regard to water content in positive electrode materials and electrolyte solutions. As this aspect was solved by the increasing availability of battery grade materials, some of the basic limitations of the battery became more evident and work was advanced to cope with these problems. Complete solutions were not found when the advent of lithium ion batteries succeeded in avoiding the most severe problems of lithium metal negative electrodes. The state of the art in 1991 will be briefly summarized and the likely directions of continued progress in lithium metal rechargeable batteries will be discussed. Also, the potential advantages and disadvantages of lithium metal batteries will be given. Finally, the state of present art of lithium metal batteries for both solid and liquid electrolytes will be presented and the likelihood of success of present approaches will be considered.

1For the history of lithium ion batteries see: G. E. Blomgren, The Development and Future of Lithium Ion Batteries,
doi: 10.1149/2.0251701jesJ. Electrochem. Soc. 
2017, 164,A5019-A5025
(Invited) Advanced Diagnosis Tools for Probing Interfaces and Surfaces in Electrochemical Systems
Authors: Meng Ying Shirley
Published: February 2020

Several high voltage cathode materials such as Li-excess layered oxide Li(LixNiCoMn)O2 and spinel LiNi0.5Mn1.5O4 are considered to be promising candidates for high-energy electrode material for Li-ion batteries, particularly for electric vehicle applications. Nevertheless, many of these high voltage cathodes suffer from poor cycle life and capacity degradation, especially at elevated temperatures. In this work new findings on surface and interface stability affecting the electrochemical longevity of the high voltage cathode material are investigated using a combination of in situ and ex situ imaging and spectroscopic tools, including: transmission X-ray microscopy, synchrotron X-ray absorption spectroscopy, and double-aberration-corrected scanning transmission electron microscopy. These tools unveil that cation migration and subsequent surface structural changes at the atomic levels are majorly responsible for the degradation. Combining the DFT + U calculations with our experimental observations, a correlation between these interface structural instability and the capacity degradation can be established. On the other hand, with the development of solid-state electrolytes, the solid/solid electrode/electrolyte interfaces present some major challenges in diagnosis methods. We will discuss some of the new diagnosis method development as well.
Multiscale Chemical Evolution of Si Electrode upon Cycling in Li-Ion Cell Using Advanced Characterization Tools
Authors: Guyomard Dominique , Boniface Maxime , Quazuguel Lucille , Danet Julien , Dupre Nicolas , Lestriez Bernard , De Vito Eric , Bordes Arnaud , Rieutord François , Lyonnard Sandrine , Moreau Philippe , Bayle-Guillemaud Pascale
Published: February 2020

Continuous solid electrolyte interface (SEI) formation remains the limiting factor of the lifetime of silicon nanoparticles (SiNPs) based negative electrodes. Methods that could provide clear diagnosis of the electrode degradation are of utmost necessity to streamline further developments.

We show that a combination of selected techniques, such as 7Li, 19F MAS NMR, XPS, TOF-SIMS and STEM-EELS, provides an in-depth characterization at different scales of the SEI layer forming on the surface of silicon particles as well as its evolution upon cycling.

We demonstrate that STEM-EELS can be used to quickly map SEI components and quantify LixSi alloys from single experiments with nanoscale resolutions down to 5 nm. Exploiting the low-loss part of the EEL spectrum allowed us to circumvent the degradation phenomena that have so far crippled the application of this technique on such beam-sensitive compounds. Our results provide unprecedented insight into silicon failure mechanisms explored at the nanometer scale in full cell configuration. We observe the morphology of the SEI to be extremely heterogeneous at the particle scale but with clear chemical evolutions with extended cycling coming from both SEI accumulation and a transition from lithium-rich carbonate-like compounds to lithium-poor ones. In addition, we were able to correlate local discrepancies in lithiation to the initial crystallinity of silicon as well as to the local SEI chemistry and morphology. Electrode failure mechanisms at the particle scale were directly observed to be related to SiNP disconnection from both electronic and ionic conduction pathways, creating strong heterogeneous lithiation processes leading to some overlithiated SiNPs. It leads to differential swelling, amplified pulverization and enhanced SEI formation. These findings suggest that capacity retention could be improved through a better control of the nanoscale homogeneity of the electrical wiring and accessibility of porosity in these highly electrolyte-reactive electrodes.

Such results emphasize the importance of achieving multiprobe, multiscale and nanoscale analysis by using various advanced characterization tools.
New Operando Technique to Detect Manganese Dissolution from Lithium Manganese Oxide Electrodes
Authors: Zhao Lihong , Chenard Etienne , Sottos Nancy R. , White Scott R.
Published: February 2020

Lithium manganese oxide is a promising cathode material for the next generation of lithium ion batteries due to its high capacity, low cost, and low toxicity. However, LMO electrode suffer from rapid capacity loss due to degradation of the active material by manganese dissolution into the electrolyte. Significant scientific effort has recently been devoted to understanding the effect of environmental and operating parameters on Mn2+ dissolution (e.g. storage temperature, electrolyte acidity and overcharge/ overdischarge conditions). Yet, no experimental data exits for Mn2+ dissolution during lithiation and delithiation, due to lack of experimental techniques to monitor the Mn2+ ion concentration in real-time in the electrolyte while the battery is in operation.

Here we report an in-operando experimental technique to detect the concentration of Mn2+ ions in electrolyte using a UV-vis probe molecule (4-(2-pyridylazo) resorcinol, PAR) and activator (1,8-bis(dimethylamino)naphthalene, proton sponge) combination. Chelation between the probe molecule and Mn2+ ion induces a color change in the electrolyte, enabling in-operando characterization of Mn2+ dissolution via spectroscopy. The probe molecule is highly selective, and can selectively differentiate trace amount of Mn2+ ions compared to concentrated Li+ ions in the electrolyte solution.

The electrolyte consisted of 1 mol/L LiPF6 in ethylene carbonate/ dimethyl carbonate (1:1 by volume). Mn2+ ions were introduced into the electrolyte by dissolving different amounts of manganese(II) acetylacetonate (Mn(acac)2). Figure 1a shows the range of color of the electrolyte with respect to the concentration of manganese ions. The electrolyte was analyzed by UV-vis spectroscopy and the absorption peak is shown to shift from 490 nm to 534 nm (Figure 1b). When the Mn2+ ion concentration is stoichiometrically lower than probe concentration, all Mn2+ ions in the solution are assumed to be chelated with the probe molecules. Thus, the absorption peak intensity of chelated molecules at the characteristic wavelength (534 nm) is proportional to concentration (Figure 1c), which follows the Beer-Lamber law. Mn2+ concentration in the electrolyte can thus be determined spectroscopically without interfering with the natural operation of Li-ion batteries.

Figure 1
Studying Break-in Phenomena in Lithium-Ion Batteries through Acoustic and Impedance Measurements
Authors: Hodson Thomas , Knehr Kevin William , Steingart Daniel A
Published: February 2020

Lithium-Ion Batteries (LiBs) have become ubiquitous in modern technologies, such as in the burgeoning electric vehicle and consumer electronics markets. After manufacturing the LiB, a period of “break-in” occurs wherein the battery experiences rapid changes in properties, such as capacity [1] and stress [2], before leveling off to a stable value. Most research in LiBs analyze the full cycle life of the battery and have little regard for the initial break-in period. However, understanding and controlling break-in conditions could determine future performance of the cell. In this study, we use electrochemical acoustic and impedance spectroscopy measurements to analyze break-in of LiBs. We further analyze how break-in conditions, such as varying the rate of current, affect the overall performance of the battery.

[1] Hong, Jong‐Sung, et al. "Electrochemical‐calorimetric studies of lithium‐ion cells." Journal of the Electrochemical Society 145.5 (1998): 1492 [2] Liu, Xinyi M., and Craig B. Arnold. "Effects of Cycling Ranges on Stress and Capacity Fade in Lithium-Ion Pouch Cells." Journal of The Electrochemical Society 163.13 (2016): A2501-A2507.
Li-Ion Cell with Reference Electrode
Authors: Ming Yang , Kwon OuJung
Published: February 2020

Individual electrode performance is an important topic in Li-ion cell research. Most studies are based on post-mortem analyses of the anode and cathode. Full cell level studies require in-situ analysis with a reference electrode. 18650 size Li-ion cells were analyzed with the 3-electrode techniques; the impedance of cathodes and anodes were independently monitored with EIS and pulse tests.
(Invited) Aluminum Layer Electrodeposition from Aqueous Solutions
Authors: Watkins John D , Zhou Xu , Nulwala Hunaid B.
Published: February 2020

The electrodeposition of reactive metals, such as aluminum and magnesium, has proven to be an elusive goal in electrochemistry. These metals represent a class of materials that are generally more environmentally friendly than transition metal complexes but due to their overwhelmingly negative reduction potentials, are generally considered impossible to deposit from aqueous solutions. These metals may, however, be electrodeposited from solutions based on organic solvents or ionic liquids, but these media must be kept rigorously dry. In the presence of even trace amounts of water, the relatively low water splitting potential, combined with the relative abundance of water instead leads to excessive gas evolution.

We will show that, by using an ionic liquid inspired ligation approach to metal deposition we were able to successfully shift the reduction potential of reactive metals much less negative. This shift allows the metal reduction to be competitive with water splitting and allows the deposition of a metal rich oxide layer from aqueous solution. These layers were found, under some circumstances to be both adherent and coherent and with thicknesses on the micron scale.

Figure 1
Electrodeposition of Nickel Selenide Thin Films
Authors: Kutyla Dawid , Kolczyk Karolina , Zabinski Piotr , Kowalik Remigiusz
Published: February 2020

Chalcogenides of transition metals such as zinc, cadmium, cobalt or nickel feature semiconducting properties making them attractive materials for applications in electronics, optics and catalysis. One of the less investigated systems is Ni-Se, although it seems to be very promising material for many purposes. Nickel with selenium can form several selenides of different stoichiometry. NiSe2 can be used as anodic material in modern batteries of high capacity. Moreover NiSe can be successfully applied as a counter-electrode in high energy solar cells. Recently, several works have been devoted to obtain electrocatalytic materials containing nickel with selenium at the same time still featuring comparable properties to noble metal based catalysts.

The article presents results concerning electrochemical deposition of Ni3Se2 from aqueous acidic solutions. The mechanism of electrode reactions in the Ni2+ - H2SeO3 – H2O system was defined with the use of cyclic voltammetry with a gold disk electrode. According to the voltammetry and hydrodynamic methods the process of nickel and selenium co-deposition is determined by the velocity of selenium ions diffusion to the electrode surface. The Ni3Se2 coatings were obtained by the potentiostatic method on copper medium. The elemental composition was determined with the XRF method. The XRD analysis indicated that within potentials from -0.6 to -1.0 V the dominating phase is Ni3Se2. The influence of applied potential and concentration of electroactive species on the elemental and phase composition and the quality of obtained coatings was determined. The surface morphology was observed with the use of scanning electron microscopy.

Acknowledgment

The authors would like to thank Polish National Science Centre for the financial support provided by the grants: No UMO-2016/21/N/ST8/00222, 2011/01/D/ST5/05743, 2016/21/B/ST8/00431 and and the research was carried out in the frames of COST Action MP1407 (e-MINDS).
(Invited) In-Situ Stress Measurements during Cobalt Electrodeposition
Authors: Stafford Gery R. , Graciano Vinicius Primo , Bertocci Ugo
Published: February 2020

Electrodeposited Co has attracted much attention over the past several decades owing in part to its interesting magnetic properties. These properties are largely dependent upon the structure and morphology of the electrodeposit, which can vary dramatically with overpotential, electrolyte pH, and the presence of strongly adsorbing anions. For example, solutions with a pH < 2.5 will generally result in a mixture of both face-centered cubic (fcc) and hexagonal close-packed (hcp) Co on Au, while more alkaline solutions yield nearly pure hcp Co. The evolution of residual stress during thin film growth also depends on deposit microstructure and growth conditions, making in situ cantilever curvature measurements a nice complement to traditional electrochemical measurements during electrodeposition.

We have measured the stress response as a function of overpotential in films measuring less than 25 nm in thickness, from 0.1 mol/L NaClO4 + 0.001 mol/L Co(ClO4)2 (pH = 4.8) and at Co current efficiencies ranging from 65% to 90%. XRD analysis indicates that under these deposition conditions the Co is face-centered cubic and maintains the (111) texture of the Au substrate, suggesting epitaxial but not pseudomorphic growth on the Au. Figure 1(a) shows the measured stress-thickness product over the deposition/stripping cycle for several deposition potentials. The corresponding steady-state stress associated with these curves varies from 0 to 450 MPa tensile, with much of the increase occurring in the potential range of -1.22 V to -1.24 V vs. SSE. However, over this potential range there is no change in grain size or growth rate, factors typically associated with tensile stress generation. Interestingly, the corresponding stripping voltammetry (Figure 1(b)) shows than an additional stripping wave appears in films deposited at potentials that correspond to the large increase in tensile stress. These additional stripping waves are typically associated with hydrogen in the film, suggesting that tensile stress can be attributed to the co-generation of hydrogen. Interstitial hydrogen is typically associated with compressive stress, or post-deposition tensile stress as the hydrogen is liberated from the film. This talk will examine additional sources of hydrogen-induced tensile stress, such as the presence of hydrogen stabilized vacancies, defects found to be quite stable in fcc Fe-group metals and alloys deposited under conditions of H+ discharge. As a counter argument, we will consider the possibility that co-generation of hydrogen may alter the energetics associated with nuclei coalescence, through modification of the Co surface energy or subsequent grain boundary energy, rather than through changes in grain size.

Figure 1
Gold-Core Transition Metal Oxide-Shell Nanoparticle Electrocatalysts for Enhanced Oxygen Evolution
Authors: Strickler Alaina Leigh , Escudero-Escribano María , Jaramillo Thomas F
Published: February 2020

The oxygen evolution reaction (OER) is important for many renewable energy technologies, including electrolyzers, CO2 reduction, and metal-air batteries. Currently, the slow kinetics of this reaction limit efficiencies of many of these technologies, necessitating the development of high performance electrocatalysts. In recent reports, Au supports have been shown to enhance the OER catalytic activity of many 3d-transition metal thin films in alkaline conditions. Herein, we translate the beneficial impact of Au supports to high surface area core-shell nanoparticles, where a Au-core is surrounded by an OER-active transition metal oxide-shell (Au@MxOy where M=Ni, Co, Fe, and CoFe). This work presents the synthesis, characterization and electrochemical performance of Au@MxOy nanoparticles and demonstrates universal activity enhancement over Au-free oxide nanoparticles. Of all the materials tested, Au@CoFeOx particles demonstrate the highest activity and stability with an overpotential of 328 ± 3 mV over two hours at 10 mA cm-2. This illustrates that strategically coupling Au support and mixed metal-oxide effects in a core-shell nanoparticle morphology is a promising avenue to device-ready, high performance OER catalysts.