bluuebunny/crossref_metadata_2025_split huggingface dataset:
Properties of Pulse Electrodeposited CuInGaSe2 Films
Authors: Murali Kollegal Ramakrishna , Chitra V 
Published: February 2020

CuIn1-xGaxSe2 films of different composition (0< x <1), were pulse electrodeposited on indium tin oxide coated glass and molybdenum substrates at 50 % duty cycle and at room temperature. The precursors used were 20 mM SeO2, 30 mM CuCl2 and the concentration of the Indium chloride and gallium chloride precursors were varied to obtain films of different composition. The deposition potential was maintained at – 0.8V (SCE). The pH was maintained at 1.5 by HCl. A microprocessor controlled pulse plating unit was used. Thickness of the films measured by Mitutoyo surface profilometer was in the range of 0.5 – 1.4 micrometer with increase of Indium concentration.
The x-ray diffraction patterns of CuIn1-xGaxSe2 films of different composition. All the figures indicate the prominent peaks corresponding to (112), (220)/(204), (312)/(116). These care characteristic of the chalcopyrite phase. No other phases were observed in the x-ray diffractograms indicating the formation of single phase material. The peaks shifted from CuInSe2 side to CuGaSe2 side as the concentration of Ga increased in the films.
Composition of the films was estimated by recording the EDS spectrum of the films deposited of different composition. It is observed that films with lower concentrations of Gallium were copper rich. As the gallium concentration increased, the films became nearly stochiometric.
The tranmssion spectra exhibits interference fringes and the value of the refractive index was estimated by the envelope method. The refractive index decreases from 2.80 to 2.35 with wavelength. The band gap of the films increased from 1.11 eV to 1.62 eV as the gallium concentration increased ( from(αhν)2 vs hν plot ). The increase in band gap at lower duty cycles is due to the small crystallites. The values of the band gap agree well with the earlier report.
The room temperature transport parameters were measured by Hall Van der Pauw technique by providing gold ohmic contact. The magnitude of the resistivity increased from 0.8 ohm cm to 23.52 ohm cm as the gallium concentration is increased. The resistivity values are comparable with an earlier report.
The PEC cells using these films exhibited low photocurrent and photovoltage. The intensity of the light falling on the films deposited at different duty cycles was kept constant at 60 mW cm-2. Films of composition CuIn0.9Ga0.1Se2 exhibited maximum photo output. The photooutput was low, hence, in order to increase the photo outpout, the films of different composition were post heated in argon atmosphere at different temperatures in the range of 450 - 550°C for 15 min. Films of composition CuIn0.7Ga0.3Se2 exhibit maximum Voc. The power output characteristics after 80s photoetching indicates a Voc of 0.70V, Jsc of 20.0 mA cm-2, ff of 0.71 and h of 14.33 %, for 60 mW cm-2 illumination.
Copper Oxide Layers Obtained Via Anodization for Electrowetting on Dielectrics
Authors: Bernasconi Roberto , Bellantone Andrea , Liberale Francesco , Magagnin Luca 
Published: February 2020

Electrowetting is a technique which allows to modify the wettability of a surface through the action of an electric field. At the time of its discovery the phenomenon was believed to have no practical use due to the electrochemical reactions occurring on the surface, which in fact limit the overall effect obtainable. In the last few decades the interest toward this technique arose and the first applications appeared. Fundamental to allow such renewed interest was the use of a dielectric hydrophobic layer interposed between the metallic surface and the electrolyte: it is known in this case as Electrowetting on Dielectric (EWOD). Possible applications of this technique include variable focal lenses, microfluidic systems and displays. The latter in particular can find possible wide industrial diffusion due to the development of the Liquavista technology by Samsung. The challenge of the next future is the transfer of the electrowetting technology from rigid and planar displays to flexible and curved ones. Flexible electronics are expected to be the technology of the future and applications include wearable devices, flexible screens and smart labels for packaging.
The present work investigates the possibility of creating compact layers of copper oxide via copper anodization for the EWOD technology. Copper was chosen instead of metals that can be more efficiently anodized due to its ease of deposition by mean of wet techniques. In fact copper can be easily electroless deposited on flexible substrates, while metals like aluminium or titanium need PVD deposition or thermal coupling techniques. Other advantages of copper include high conductivity and good mechanical properties. The first part of the study involves the fundamental study of electrowetting on copper oxide coated with a fluoropolymer. Hysteresis and saturation of contact angle are analysed, as well as the adherence of the behaviour to the Young-Lippman equation. In the second part a flexible substrate is tested for electrowetting on a curved surface. Such specimen is manufactured by electroless plating of copper on PET, anodizing the resulting layer and coating the oxide layer thus obtained with a fluoropolymer. Finally the result is compared with an equivalent sample obtained coupling an aluminium layer with a polymeric substrate and thermally bonding them. The result is then anodized to obtain a compact oxide layer and coated with the fluoropolymer.
Development of Silver-Carbon-Nanotube Metal Matrix Composites for Metal Contacts on Space Photovoltaic Cells
Authors: Abudayyeh Omar Kamal , Nelson Cayla , Han Sang , Gapp Nathan , Wilt David 
Published: February 2020

The advanced solar cells used in space vehicles today are rapidly moving towards thin-film-based inverted metamorphic multijunction (IMM) solar cells mounted on flexible substrates. However, the IMM cells are more prone to cracking than state-of-the-art triple junction cells. The cell cracking can lead to metal contact failure on IMM cells, compromising the power generation. To mitigate the power loss and increase the lifetime of IMM cells, silver metal films imbedded with carbon nanotubes (CNTs), otherwise known as metal matrix composites, have been developed and investigated for the reinforced mechanical strength against stress-induced cracking. We have primarily focused on (1) surface functionalization of CNTs to make their surface more hydrophilic and wetting to metals, (2) optimization of a cyanide-free electrochemical deposition of silver, (3) electrochemical deposition, drop casting and nanospreader technique to control the composite microstructure, and (4) mechanical and electrical characterization of the composite films. We observe that carboxylation of CNTs produces a stable, homogeneous suspension of negatively charged CNTs at pH > 6. Lustrous-mirror-finish silver films are also successfully deposited, using a commercial cyanide-free silver-plating solution with precise control of current density. Currently, one of the microstructures being explored is a silver-carbon-nanotube layer-by-layer structure, where the surface coverage of CNTs is an important parameter that directly affects the CNT packing fraction and metal intercalation through the CNT network. We quantify the CNT surface coverage as a function of different deposition variables by digitally analyzing scanning electron microscopy images. In this presentation, we will further discuss how this surface coverage correlates to the mechanical and electrical properties of the MMC films. We characterize the mechanical properties, using nanoindentation and strain failure tests. The initial nanoindentation analysis reveals that the composite film has a lower elastic modulus (10 GPa) than pure silver (73 GPa), which is contrary to our initial prediction given the high elastic modulus of CNTs (1000 GPa). The lower elastic modulus is attributed to the electroplating process of silver, in which hydrogen is incorporated and trapped within the composite. Our finite element analysis also corroborates this speculation, where the elastic modulus near 10 GPa is predicted with approximately 4% void fraction. While the composite elastic modulus is lower than that of pure silver, the strain failure tests show that carbon nanotubes can bridge 20 to 50-μm-wide microcracks, maintaining electrical conductivity of the composite
(Invited) Electrochemical Processing of Metal-Insulator-Semiconductor (MIS) Photoelectrodes
Authors: Esposito Daniel , Labrador Natalie Yumiko 
Published: February 2020

Photoelectrochemical (PEC) water splitting is a promising route to solar-driven H2 production, but the efficiency and stability of semiconducting photoelectrodes must be improved. One potential approach to achieving high efficiency and good electrochemical stability is the metal-insulator-semiconductor (MIS) photoelectrode design. [1-4] The MIS arrangement generally consists of catalytic metal structures, or collectors, deposited on an oxide-covered semiconductor as illustrated in Fig. 1. A crucial element of this design is the insulating oxide layer, which protects the semiconductor from the potentially corrosive electrolyte while facilitating minority carrier tunneling between the semiconductor and collectors. The oxide layer must be ultra-thin (1-3 nm) and exhibit minimal defects at the SiO2/Si interface in order to facilitate efficient tunneling and maximize photovoltage.
In this work, we have systematically investigated electrodeposition of Pt nanoparticle collectors on SiO2-covered p-Si(100) MIS photoelectrodes, with the goal of obtaining a high degree of control of nanoparticle coverage, catalytic surface area, and nanoparticle size. These three parameters strongly influence photoelectrode optical, catalytic, and photovoltage performance, respectively, and electrodeposition offers an exciting opportunity to optimize these properties. This work has studied the influence of key deposition parameters (potential, current density, surface treatment) on the physical properties of the Pt nanoparticles, as well as the resulting PEC performance for photo-driven hydrogen evolution reaction (HER). Through systematic investigation of the structure-property relationships in this MIS photoelectrode system, this study deconvolutes the optical, electronic, and catalytic influences of Pt nanoparticle geometries on photoelectrode performance. Such loss analysis is highly useful for guiding the design of more efficient photoelectrodes. Finally, opportunities and challenges of utilizing electrochemical processing for the manufacture of efficient photoelectrodes are discussed.

References

1. H.J. Lewerenz, et al., Electrochem. Acta, 56, 10726 (2011).
2. A.G. Munoz and H.J. Lewerenz, ChemPhysChem, 11, 1603 (2010).
3. Y. Chen, P. McIntyre, et al., Nature Materials, 10, 539 (2011).
4. D.V. Esposito, I. Levin, T.P. Moffat, A.A. Talin, Nature Materials, 12, 562 (2013).

Figure 1
Formation of Si Nanowires By Electroreduction of Porous Ni/SiO2 Blocks in Molten CaCl2
Authors: Fang Sheng , Yang Juanyu , Wang Han , Yu Bing , Lu Shigang 
Published: February 2020

Electroreduction of porous SiO2 in molten CaCl2 is a promising approach to prepare silicon nanowires (SiNWs) in large quantities. However, it is difficult to control the morphologies and surface topologies of the produced SiNWs. In this work, pure nickel metal powders are added into SiO2, and SiNWs with straight morphology are prepared by electroreduction of solid Ni/SiO2 blocks in molten CaCl2 in a wide temperature range. The prepared SiNWs have a diameter distribution of 80 to 350nm, and nickel silicide is found at the tip of the nanowire. Cyclic voltammograms indicate that nickel does not change the mechanism of electrochemical reduction of SiO2. The growth process of SiNWs is investigated by XRD, FESEM, HRTEM, EDS, and SAED. It is confirmed that nano-sized nickel-silicon droplets formed at the Ni/SiO2/CaCl2 three-phase interface lead the growth of SiNWs, and adding nickel metal into SiO2 can promote the growth of straight nanowires during the electroreduction of Ni/SiO2 in molten CaCl2.
Silane-Free Adhesive Electroless Deposition of a Nickel/Phosphorous Layer on Si Wafer
Authors: Wei Tzu Chien , Hsu Chin Wei , Wang Wei-Yan , Chen Chih-Ming , Lai Kuei-Chang 
Published: February 2020

Electroless deposition (ELD) of nickel/phosphorous (Ni/P) layers has been a valuable method for creating diffusion barriers in the silicon (Si) industry, particularly in the formation of metal contact or interconnection structure in integrated circuits or microelectromechanical systems [1,2]. The ELD of Ni/P layers is a catalytic reaction that requires either a trace amount of seed Ni [3] or noble metals such as palladium [4] to lower the activation energy for nucleation and growth. Because the ELD process occurs on the catalyst-attached Si surface, the adhesion of Ni/P films is related to the interfacial properties of the catalyst and Si surface. In the first part of this presentation, we develop a post-annealing-free, adhesive Ni/P layer on an aminosilane-modified (ETAS-modified) Si surface through an ELD catalyzed by a novel, home-made polyvinylpyrrolidone-capped palladium nanocluster (PVP-Pd). X-ray photoelectron spectroscopy analysis reveals that ETAS was covalently bonded on the Si surface, whereas the amino groups on ETAS bridged with the palladium core in the PVP-Pd. Because of above two effects, the ELD Ni/P layer showed superior adhesion on the Si wafer without the need of conventional post-annealing treatment. Compared with the Ni/P films deposited on bare Si surfaces by using commercial Sn/Pd colloids, the adhesion of the Ni/P film catalyzed by either PVP-Pd on the ETAS-modified Si wafer improved more than 4-fold.
Later on, we report our new finding regarding to prepare adhesive ELD Ni/P film on Si wafer without the requirement of silane-modification and post annealing by innovating catalyst system. Switching from PVP-Pd to polyvinyl alcohol-capped palladium nanocluster (PVA-Pd), it is found the surface modification by aminosilane-compound can be omitted, while the resulting ELD Ni/P film still exhibits adequate adhesion.
Reference:
[1] S. Furukawa, M. Mehergany, Sensors Actuators 56 (1996) 261.
[2] K.Y. Lee, J.T. Huang, P.S. Chao, J.M. Lin, H.J. Hsu, Microelectron. Eng. 113 (2014) 147.
[3] S.J. Cherng, C.M. Chen, W.P. Dow, C.H. Lin, S.W. Chen, Electrochem. Solid-State Lett.
14 (2011) P13.
[4] C. R. Shipley Jr., U.S. Pat. 3,011,920 (1961).
Advancements in Copper Interconnect Technology: The Effect of Sulfuric Acid on the Adsorption & Desorption of an Advanced MLI Suppressor
Authors: Olson Wyatt , Schmidt Manning , Wetterer Anna , Willey Mark 
Published: February 2020

In the last five years the size of the copper plated interconnect features for the logic and memory market has dropped below 30nm. This decrease in size has forced plating chemistries to operate on copper seed that is often times either non continuous or has morphology that requires special tuning of the additives to create the bottom up phenomenon. In the past, the traditional path of development led to the continued optimization of the organics additives (accelerators, suppressors, levelers) to help generate the void free fill in the plated interconnects while mostly fixing the inorganic concentrations. A new approach to additive development is to optimize the organic additives in different electrolyte concentrations.
Traditionally, the copper chemical vendors were focused on the traditional 40g/L Cu2+, 10g/L sulfuric acid, 50ppm electrolyte formulation. However, optimization of electrolytes can allow for a decrease in defectivity across the wafer. This change in electrolyte formulation has sparked a new set of chemistry development at MLI to tune the organic chemistry to the electrolyte concentrations and also expand the understanding of the effect of electrolyte on the organic additives.
The current set of work aims at showing how acid affects the adsorption and desorption of a new advanced MLI suppressor. This work starts with a basic understanding of how acid affects the plating bath with no suppressor present and then expands to show how this new suppressor is affected by the acid changes. A surface adsorption and desorption model is then hypothesized based on the electrochemical signal.
The figure below outlines a typical adsorption result where an applied current of 10mA/cm2 is run while solution over the electrode is transitioned from one containing the electrolyte only to one containing the electrolyte and the MLI suppressor.
The two plots in the graph show the difference in the adsorption rate as a function of acid concentration. One will note that the higher acid concentration shows a stronger steady state suppression and also a slower adsorption rate. Experiments similar to these will be disclosed and the adsorption / desorption model discussed.

Figure 1
Coupling Phenomena Between Micromorphological Evolution and Ionic Mass Transfer Rate during Ag Electrodeposition in AgNO3 Aqueous Solution
Authors: Fukunaka Yasuhiro , Wakatsuki Takao , Homma Takayuki 
Published: February 2020

The rechargeable battery concept with maltreat tolerance and safety is essentially indispensable not only in the space application but also in terrestrial renewable energy storage systems. Higher energy density, power capability and longer life requirements make the targets more challenging. A better understanding of the electrolyte/electrode interface phenomena including electrode kinetics is crucial. “Electrochemical Nucleation & Growth” aspect is a fundamental approach how to control the coupling phenomena between nano-structural interface evolution and ionic mass transfer rate enclosed a meso-scale space filled with electrolyte. Such a research has not been frequently challenged in designing the longer life energy storage devices.
Metal negative electrode surface shows various morphologies after repetition of electrodeposition and electrochemical dissolution reaction. Dendrite precursor is finally grown after electrochemical nucleation and growth process where the coupling phenomena govern. It is also indispensable for us to prolong the charging/discharging operation of secondary battery after longer term utilization under various environments. For liquid electrolyte, a precise study of these morphologies may be complicated by convective motion caused by gravitational force of buoyancy. Now the coupling phenomena are discussed in the case of silver because it has been employed as negative electrode in space application.
3M AgNO3 aqueous solution was contained in a quasi-2D cell. Holographic interferometry was employed to monitor the ionic mass transfer rate. The concentration profiles were formed around dendrite tips of silver electrodeposited at extremely high current densities. A uniform diffusion layer was formed along the cathode surface at the start of electrolysis. Following a certain incubation period, several dendrite tips began to protrude into the diffusion layer. The growth rates of these dendrites were related to concentration gradients around the tips, diffusivity, and transfer number of Ag+ ion. Giant-Macro step flow accompanied with Ag dendritic growth was dynamically observed with Laser Confocal Scanning Microscope.
Transient current variation measurements are now engaged under the double pulse potential which introduces Ag nucleus on the foreign substrate in order to develop a multi-scale physical model of dendritic growth.
Nanoparticle Electrocatalysts for the Oxidation of Biomass
Authors: Arroyo-Torres Christian , Staser John A , Movil-Cabrera Omar 
Published: February 2020

Biomass fuels come from things that once lived: wood products, dried vegetation, crop residues, aquatic plants and even garbage. Lately, there is a constant supply of waste – from construction and demolition activities- in which this waste is generally burned during the chemical recovery process to generate heat. Unfortunately, catalytic processes are difficult to implement for the degradation of biomass because selective oxidation is difficult and these processes produce an unacceptable amount of solid residue like char. Electrochemical processes, on the other hand, have several advantages over catalytic processes, including the use of mildly basic solvents as electrolytes, and control over the rate of reaction and the products. Thus, the electrochemical oxidation of biomass would be an ideal process to utilize this renewable raw material. We have begun to investigate the mechanism of biomass oxidation via electrochemical processes, in which several proceeding chemical or electrochemical reactions are possible. We will present GC/MS data that identify biomass oxidation products. This process could provide an economic way of reducing the organic waste from bio-refinery industries.
3D Printed Membraneless Water Electrolysis Cells
Authors: O'Neil Glen D , Esposito Daniel 
Published: February 2020

Hydrogen (H2) has emerged as a promising candidate for both clean energy storage and as an alternative to fossil fuels. Currently, the majority of H2 is produced via methane reformation, which emits one molecule of CO2 for every three molecules of H2 and thus contributes to climate change.1 Alternative methods towards H2 production include direct photoelectrochemical water-splitting using semiconducting photoelectrodes,2 or using a membrane electrode assembly (MEA), which can be powered using renewable power sources. Direct production of H2 using semiconductor photoelectrodes is very promising, but there are issues remaining with electrode stability and efficiency. While remaining the industry standard, electrolysis using a MEA is costly and is most commonly performed in acidic solutions.
Here we present novel device architectures for water splitting which utilizes additive manufacturing (e.g. - 3D printing) to produce hydrogen and oxygen gas with minimal product crossover. Additive manufacturing has the benefits of: low-cost, ability to rapidly prototype, and use renewable materials (e.g. – poly(lactic acid)).3 In our design, a flowing electrolyte solution impinges upon two electrodes, which are placed in close proximity to minimize solution resistance (measured to be ~3 Ω in 0.25 M H2SO4). The low Ohmic losses enable current densities up to 300 mA cm-2, and can be used in acidic, basic and neutral electrolytes because no membrane is required. The product gas streams are separated by a thin divider placed downstream of the electrodes, so that product crossover is essentially zero. The results compare well with previously reported studies,4 but eliminate the complicated processing times and device complexities required.

References

(1) Navarro, R. M.; Peña, M. A.; Fierro, J. L. G. Hydrogen Production Reactions from Carbon Feedstocks: Fossil Fuels and Biomass. Chem. Rev.
2007, 107, 3952–3991.
(2) Walter, M. G.; Warren, E. L.; McKone, J. R.; Boettcher, S. W.; Mi, Q.; Santori, E. A.; Lewis, N. S. Solar Water Splitting Cells. Chem. Rev.
2010, 110, 6446–6473.
(3) Chisholm, G.; Kitson, P. J.; Kirkaldy, N. D.; Bloor, L. G.; Cronin, L. 3D Printed Flow Plates for the Electrolysis of Water: An Economic and Adaptable Approach to Device Manufacture. Energy Environ. Sci.
2014, 7, 3026–3032.
(4) Hosseini Hashemi, S. M.; Modestino, M. a.; Psaltis, D. Membrane-Less Microelectrolyzer for Hydrogen Production across the pH Scale. Energy Environ. Sci.
2015, DOI: 10.1039/C5EE00083A.