bluuebunny/crossref_metadata_2025 huggingface dataset:
Structures and Reactivity of Group 9 Metalloporphyrin Complexes
Authors: Anding Bernie J. , Dairo Taiwo O. , Woo L. Keith
Published: February 2020

The importance of metalloporphyrins is highlighted by their wide occurrence and use in nature.  Essential biological roles of metalloporphyrins include electron-, energy-, and oxygen-transfer, oxygen activation, and diverse functions in enzyme active sites.  Due to a broad range of physical and chemical properties, metalloporphyrins have been modified for a variety of applications such as novel components in advanced materials, sensors, medical research, and synthetic chemistry.  Metalloporphyrins are also of great utility for non-biological chemical catalysis, spanning reactions such as aziridination,1 C-H activation,1 and olefination.2  Moreover, metalloporphyrins are useful, atom-efficient catalysts for the generation of new carbon-carbon and heteroatom bonds using diazo carbonyl compounds.1 Thus, understanding the structures and reactivities of metalloporphyins is vital for developing and optimizing new uses.

Our current work focuses on group 9 (Rh, Ir) metalloporphyrins.  This includes probing the reactivity of coordination complexes and determining the structures of the subsequent products.3 Recently, tetratolylporphyrinato (TTP) methyliridium, Ir(TTP)CH3, was shown to be an active and robust catalyst for the cyclopropanation of olefins using diazo reagents as carbene sources.4  Ir(TTP)CH3 also catalyzes N–H insertion reactions between ethyl diazoacetate (EDA) or methyl phenyldiazoacetate (MPDA) and a variety of aryl, aliphatic, primary, and secondary amines.5  Reactions with aryl amines produce the highest yields with up to 105 catalyst turnovers and without the need for slow addition of the diazo reagent. Mechanistic aspects of diazo insertion reactions are examined.  In addition, a comparison of the molecular structures of RhIII(TTP) and IrIII(TTP) carbene complexes provides insights for understanding reactivity differences for the two metals complexes.6

References

1.  Anding, B. J.; Woo, L. K. In Handbook of Porphyrin Science; Kadish, K. M., Guilard, R., Smith, K., Eds.; World Scientific Publishing Company: Hackensack, NJ, 2012; Vol. 21, p 145.

2.  Mirafzal, G. A.; Cheng, G.; Woo, L. K. J. Am. Chem. Soc.
2002, 124, 176-177.

3.  Dairo, T. O.; Ellern, A.; Angelici, R. J.; Woo, L. K. Organometllics, 2014, 33, 2266-2276.

4.  Anding, B. J.; Ellern, A.; Woo, L. K. Organometallics
2012, 31, 3628-3635.

5.  Anding, B. J.; Woo, L. K. Organometallics, 2013, 32, 2599-2607.

6.  Anding, B. J.; Ellern, A.; Woo, L. K. Organometallics, 2014, 33, 2219-2229.

Figure 1
Asymmetric Oxidation and Carbene Transfer Reactions Catalyzed By Metalloporphyrins in Water
Authors: Simonneaux Gerard , Le Maux Paul , Carrie Daniel , Chevance Soizic
Published: February 2020

The development of environmentally benign reactions is an important goal in synthetic organic chemistry and chemical engineering. However, catalytic enantioselective reactions using transition-metal complexes in protic or aqueous solvents are within limited ranges. The current applications of asymmetric catalysis using metalloporphyrins will be reported (1). Distinct methodologies have been developed for carbene transfer and oxidation reactions such as the use of water-soluble catalysts (2). Comparison between hydrophobic and hydrophilic solvents will be discussed from an asymmetric point of view.

Catalytic enantioselective oxidations using transition-metal complexes are limited when the oxidant is hydrogen peroxide. The two main difficulties of using hydrogen peroxide in the presence of transition metal complexes are the homolytic cleavage generating OH radicals and the catalase reaction with formation of dioxygen. Asymmetric sulfoxidation, epoxidation of alkenes and hydroxylation catalyzed by iron and manganese porphyrins will be described (3). Thus the asymmetric epoxidation of styrene derivatives by H2O2 (or UHP) to give optically active epoxides (ee up to 81%) and hydroxylation of alkanes to give optically active secondary alcohols (ee up to 78%) were carried out in methanol and water using chiral water-soluble iron porphyrins as catalysts.

(1) Recent Advances in Catalysis by Water-Soluble Metalloporphyrins

G. Simonneaux, P. Le Maux, S. Chevance and H. Srour. Handbook of Porphyrin Science, 2012, Vol. 21, 377-410

(2) Enantioselective Manganese-Porphyrin-Catalyzed Epoxidation and C-H hydroxylation with Hydrogen Peroxide in Water/Methanol Solutions

  H. Srour, P. Le Maux and G. Simonneaux. Inorg. Chem. 2012, 51, 5850-5856.

(3) Metal-catalyzed asymmetric sulfoxidation, epoxidation and hydroxylation by hydrogen peroxide

Hassan Srour, Paul Le Maux, Soizic Chevance, Gérard Simonneaux. Coord. Chem. Rev., 257 (2013) 3030– 3050
Catalytic Activity of Novel Vitamin B12 Derivatives
Authors: Gryko Dorota
Published: February 2020

Among many biologically important metals, Co, in the form of vitamin B12 (cyano-cobalamin), plays a unique role. B12 coenzymes are indispensable for catalyzing enzymatic rearrangements (coenzyme B12, adenosylcobalamin) and methylation reactions (methylcobalamin).1 The special ability of vitamin B12 and other corrinoids to form a Co-C bond, combined with its facility in furnishing alkyl radicals via homolysis, has attracted the interest of many researchers, because corrinoids can be used as catalysts for C-C-bond forming reactions, which belong to the most challenging processes in organic synthesis. These catalytic reactions typically involve alkyl-cobalt complexes, which are formed in reactions of Co(I) species and an electrophile or a Co(II) and a radical. The most common chemical procedure utilizes the ‘supernucleophilicity’ of the Co(I) species (B12s) toward alkylating agents, such as alkyl halides. Homolysis of the Co-C bond generates a carbon-centered radical, which can, in situ, disproportionate, abstract H˙, or self-couple. In these reactions, B12 alkyl derivatives can be considered ‘reversible carriers’ of an alkyl radical.4

We have developed the synthesis of novel cobalamin derivatives possessing modified substituents at the periphery of the molecule. Our methodology presents a unique situation in which the six peripheral amide groups are transformed while leaving the bottom “f-loop” intact.2 These derivatives displayed UV-Vis spectra and oxidation-reduction characteristics similar to those of vitamin B12 but they differed significantly from the”incomplete” corrinoid heptamethyl cobyrinate, where the nucleotide moiety is absent, and instead, the second cyanide is coordinated. We confirmed that the intramolecular coordinating ligand plays a role in the radical reactions catalyzed by vitamin B12 derivatives. For example, the microwave-assisted homocoupling of benzylbromide3 catalyzed by cobalester produced a higher yield when compared to reactions catalyzed by reduced (CN)2Cob(OMe)7.Furthermore, the amphiphilic character of these newly synthesized derivatives facilitates carbon insertion into the vinyl C-H bond of olefins with alkyl diazoacetates in the presence of light.

1.   Banerjee, R. Chemistry and Biochemistry of B12, John Wiley & Sons, Inc, 1999

2.   Proinsias ó, K.; Giedyk, M.; Sharina, I.G.; Martin, E. and Gryko, D. ACS Med. Chem. Lett.
2012, 3, 476.

3.  Giedyk, M.; Fedosov, S.; Gryko, D. Chem.
Commun.
2014, 50, 4674-4676.

4.   Shey, J.; McGinley, Ch.M.; McCauley, K.M.; Dearth, A.S.; Young, B.T. and van der Donk, W.A. J. Org.
Chem.
2002, 67, 837.

Figure 1
Synthesis, Redox Properties and Structural Features of Expanded Isophlorins
Authors: Anand Venkataramanarao Govindan , Gopalakrishna Tullimilli Yadagiri
Published: February 2020

The expanded derivatives of isophlorin provide sufficient examples for Huckel’s 4nπ anti-aromatic systems. They vary significantly in their electrochemical properties compared to the aromatic expanded porphyrins. In comparison to the small macrocycles, the large and planar expanded isophlorins exhibit reversible two-electron oxidation. The structure of these macrocycles also undergo reversible structural transformation between planar and figure of eight conformations accompanying the redox process. The oxidized product could be identified as aromatic dication or as a polaron pair depending on the size of the macrocycle. The number of non-pyrrolic heterocyclic units is crucial to stabilize aromatic, antiaromatic or neutral radical isophlorin. A stable 25π neutral radical identified in a one-pot synthesis, exhibits reversible one electron redox to form 24π anti-aromatic cation and a 26π aromatic anion. Synthesis, experimental details and structural features of expanded isophlorins will be highlighted in this presentation.

References:

1. T. Y. Gopalakrishna, J. S. Reddy and V. G. Anand, Angew. Chem. Int. Ed., 2013, 52, 1763.

2. T. Y. Gopalakrishna and V. G. Anand, Angew. Chem. Int. Ed., 2014, 53, 6678.

3. T. Y. Gopalakrishna, J. S. Reddy and V. G. Anand, Angew. Chem. Int. Ed., 2014, 53, 10984
Synthesis and Unique Spectroscopic Properties of Main Group Element Phthalocyanine and Tetraazaporphyrin Complexes
Authors: Kobayashi Nagao , Furuyama Taniyuki , Satoh Koh , Yoshida Takuya , Kushiya Tomofumi
Published: February 2020

Phthalocyanines (Pcs) generally have strong absorption bands in the 650-680 nm region, which are referred to as the Q-bands and have been assigned to the transition between the HOMO and the LUMO of the Pc p-system. Although attempts to shift the Q-band to the near-IR region have been carried out by many researchers, nobody has so far succeeded in shifting the band beyond 1000 nm. To address this, Pcs with electron-donating group 16 (S, Se, and Te) atoms at the peripheral, so-called a positions, coordinating a group 15 (P, As, and Sb) ion, have been synthesized through a process of rational design based on a consideration of the size of MO coefficients in the frontier p-MOs [1]. The introduction of the group 16 elements at the a positions results in a red shift of the Q band from the 650-680 nm region to ca. 800 nm, due mainly to a destabilization of the HOMO. The introduction of group 15 elements in the +5 oxidation state to the central cavity results in a further red shift of the Q-band to the 1020-1060 nm region, due to a marked and moderate stabilization of the LUMO and HOMO, respectively (Fig. 1). In contrast, when group 15 (P, As) elements were coordinated by tetra-phenylated tetraazaporphyrins (TAPs), completely unexpected and highly unusual absorption bands were observed between the Soret and Q-band regions (Fig. 1). MO calculations carried out for a series of compounds with different substituents at the para-position of the phenyl groups predicted that these bands can be assigned to charge-transfer (CT) transitions from the peripheral aryl substituents to the TAP core.[2] Because of the presence of these CT bands, the TAPs in this study effectively absorb across the complete UV-visible region(300-700 nm) as single, discrete chromophores.

References: [1] Furuyama T, Sato K, Kushiya T, Kobayashi N. J. Am. Chem. Soc.2014; 136: 765-776.                                                        [2] Furuyama T, Yoshida T, Hashizume D, Kobayashi N. Chem. Sci. 2014; 5: 2466-2474.

Figure 1
Electrochemical Gating of Charge Transport in Single Macrocycle Molecular Switches
Authors: Borguet Eric
Published: February 2020

Molecular switches, i.e., molecular scale devices that can be turned on and off, are of long standing interest.  In the quest for miniaturization of electronic devices, the development of electrical switches of molecular dimensions has been identified as an important target of practical importance. While much progress has been made in designing functional molecular scale electrical switches, i.e., molecular cores whose intrinsic conductivity can be externally modulated, the question of contact resistance has not been sufficiently addressed.

Our novel strategy for the regulation of charge transport through single molecule junctions combines external stimuli using a variation of electrode potential in an electrochemical environment, internal modulation of molecular structures and optimization of anchoring groups.  Our synthetic collaborators have designed redox-active benzodifuran (BDF) compounds as functional electronic units which we have used to fabricate metal-molecule-metal (m-M-m) junction devices by scanning tunneling microscopy (STM) and mechanically controllable break junctions (MCBJ).[1]  The conductance of BDF terminated thiol, the standard anchoring group for molecular scale electronic components, can be tuned by changing the electrode potentials in an ionic liquid electrolyte to show a clear single molecule field effect transistor (FET) behavior.

We hypothesized that we could optimize the response by appropriate choice of molecular anchoring group.[2]  Guided by our earlier investigations, a BDF molecule tailored with carbodithioate (-CS2-) anchoring groups was synthesized.  Our studies show that replacement of thiol by carbodithioate not only increases the junction conductance, but also substantially improves the FET response by enhancing the on/off ratio from 2.5 to 8.

[1] Regulating a Benzodifuran Single Molecule Redox Switch via Electrochemical Gating and Optimization of Molecule/Electrode Coupling, Zhihai Li, Hui Li, Songjie Chen, Toni Froehlich, Christian Schönenberger, Michel Calame, Silvio Decurtins, Shi-Xia Liu and Eric Borguet, Journal of the American Chemical Society 136, 25 8867-8870 (2014).

[2] Optimizing Single-Molecule Conductivity of Conjugated Organic Oligomers with Conjugated Carbodithioate Linkers, Yangjun Xing, Tae-Hong Park, Ravindra Venkatramani, Shahar Keinan, David  N. Beratan, Michael J. Therien, and Eric Borguet, Journal of the American Chemical Society 132 (23), 7946-7956 (2010).

Figure 1
Corrosion Studies on Graphite Encapsulated FeCo Nanoparticles Modified Black Chrome (MBC) Spectrally Selective Coatings
Authors: Usmani Belal , Vijay Vivek , Chhibber Rahul , Dixit Ambesh
Published: February 2020

Black chrome (BC) and graphite encapsulated FeCo nanoparticles modified black chrome (MBC) composite thin films were prepared on stainless steel substrates using electrodeposition technique under galvanostatic condition. Three different weight proportions of GE FeCo NPs, 0.025, 0.05, and 0.1 wt% in 200mL in black chrome electrolyte bath solutions were used for MBC thin film synthesis. A saline environment of 3.5% NaCl solution was used to carry out cyclic voltammetric and Tafel studies to understand the impact of corrosion on BC and MBC solar selective coatings. We carried out structural, microsctrucural, optical, vibrational and mechanical studies on these pristine (BC & MBC) and saline environment treated solar selective coatings. We observed that roughness and grain size of MBC solar selective surfaces decrease with increase in weight % of graphite encapsulated FeCo NPs during corrosion. More interestingly, after Tafel measurements, mechanical studies on MBC coatings showed enhanced hardness and Young’s modulus with respect to pristine BC coatings.

Keywords: Electrodeposition; Black Chrome; Graphite encapsulated FeCo NPs, Solar selective coatings
Evaluation of Dezincification Corrosion of Brass By Electrochemical Impedance
Authors: Hoshi Yoshinao , Tabei Kozue , Shitanda Isao , Itagaki Masayuki
Published: February 2020

The dezincification corrosion of the brass has been investigated to obtain the fundamental knowledge concerning the selective dissolution mechanisms. Pickering et al. (1-3) reported that a porous Cu-rich layer was formed on the brass surface due to the selective dissolution of Zn from brass. They classified the dissolution of the binary alloy into two types, which is the selective dissolution and simultaneous dissolution.

In the present work, we investigated the dissolution of brass by an electrochemical impedance spectroscopy (EIS). The EIS enables us to discriminate the time constants of elementary steps in the dissolution process. The Cu-enriched layer was formed on the brass surface by following method: The galvanostatic polarization of the brass was performed at 1.0 mA/cm2 for 24 h in the electrolyte solution of 0.5M NaCl containing 5mM NaHCO3. The temperature of the electrolyte solution was keep at 60 oC by thermostatic bath.  In order to investigate the porous structure of the Cu-enriched layer formed on the brass surface due to dezincing, the impedance spectrum was measured to examine the current distributions within the pores. In addition, impedance and complex capacitance corresponding to the typical equivalent circuits involving a transmission line model (TLM) are discussed to propose the evaluation method for the dezincification of brass.

Reference

1.               H. W. Pickering and C. Wagner, Journal of the Electrochemical Society, 114, 698 (1967).

2.               H. W. Pickering, Journal of the Electrochemical Society, 115, 143 (1968).

3.               H. W. Pickering and P. J. Byrne, Journal of the Electrochemical Society, 116, 1492 (1969).
Study of Cu Bimetallic Corrosion and Its Inhibition Strategy for Cu Interconnect Application Using Micro-Pattern Corrosion Screening
Authors: Chyan Oliver , Goswami Arindom , Koskey Simon , Yu Kyle
Published: February 2020

Ru and other noble metals have been actively investigated for use as seedless liner/barrier materials for advanced Cu interconnect applications. Due to the lack of volatile byproducts in the reactive ion etching of Cu, the Cu interconnects are fabricated by dual damascene patterning process that involves etching a trench/via pattern into a dielectric, the blanket deposition of a diffusion barrier followed by Cu electroplating, and finally removal of Cu overburden by chemical-mechanical planarization (CMP). Since the CMP process exposes the Cu interconnect and metal barrier to the continual presence of corrosive chemicals, the resulting bimetallic corrosion between Cu and diffusion barrier metal can be detrimental to the overall production yields of integrated circuit devices. In this paper,  we will present findings from a new corrosion screening metrology utilizing micro-corrosion test patterns (Cu dots, D≈130µm) to provide rapid in-situ corrosion evaluations in manufacture relevant chemical environments used to produce Cu interconnect structure. The results from Cu micro-pattern corrosion screening corroborate well with XPS and electrochemical techniques to reveal the detailed bimetallic corrosion mechanisms in specific chemical environments. For most of the CMP solutions studied to date, the Cu corrosion was found to be accelerated through an oxygen reduction reaction catalyzed by Ru. The new insights obtained from mechanistic investigation on Cu/Ru bimetallic corrosion not only help to unveil the real functions of each chemical previously masked by the complex matrix of CMP formulation, it also significantly expands the chemistry tool set that enables better corrosion inhibition strategy to protect detrimental corrosion defects of Cu interconnect with minute nanometer dimension used in advanced IC device. For example, micro-pattern corrosion screening results and electrochemical analyses revealed that 1mM pyrazole in 8 wt.% tetramethyl ammonium hydroxide (TMAH)  solution could inhibit Cu corrosion more effectively than 10mM benzotriazole (BTA) in the same solution. Overall Cu corrosion rate in TMAH based highly alkaline post CMP cleaning solution is shown to be considerably reduced to <1Å/min by addition of pyrazole as corrosion inhibitor.
Growth of TiO2 Nanotube Layers on Ti Substrates with Different Microstructures
Authors: Kim Min Su , Yamamoto Shota , Tsuchiya Hiroaki , Fujimoto Shinji
Published: February 2020

Since the reports on self-organized tubular oxide layers on Ti and its alloys by Assefpour-Dezfuly et al[1] and Zwilling et al[2,3], TiO2 nanotube layers have been widely studied in several application fields owing to its unique chemical and physical properties. It was reported that the morphology of the oxide layers is strongly influenced by anodization parameters such as electrolytic composition, applied voltage and electrolyte temperature. However, among the many anodization parameters, the influence of titanium substrate on oxide layer growth has not been clear yet. In the present study, the growth behavior of nanotubular oxide layers was examined by using Ti substrates with various microstructures.

As-received Ti sheets (purity: 99.5%) were heat-treated at 500 °C for 12 h to ensure homogeneity. After the homogenization, some Ti sheets were heat-treated at various temperatures in argon atmosphere. Also, the other sheets were subjected to ARB (Accumulative Roll Bonding) process up to 6 cycles to change the microstructures. Anodization was carried out at 50 V for 3 h in ethylene glycol containing 2 wt% H2O and 0.05 M NH4F. After the anodization, the morphology of oxide layers was characterized by FE-SEM.

Nanotubebular oxide layers were formed on all Ti sheets whereas the growth of nanotubular oxide layer was affected by the microstructure of Ti substrate that can be controlled by heat treatment and ARB process. The grain size increased with increasing heat-treatment temperature, duration while increasing the number of ARB cycle decreased the grain size. Consequentially, nanotubular oxide layer thickness increased with decreasing grain size. Therefore, it was found that the growth behavior may be affected by the numerous lattice defects in substrate introduced by heat-treatment and ARB process.

References

[1] M. Assefpour-Dezfuly, C. Vlachos, E. H. Andrews. Journal of materials science (1984): 3626-3639.

[2] V. Zwilling, E. Darque-Ceretti, A. Boutry-Forveille, D. David, M. Y. Perrin1 and M. Aucouturier. Surface and Interface Analysis (1999): 629-637.

[3] V. Zwilling M. Aucouturier, E. Darque-Ceretti. Electrochimica Acta, (1999): 921-929.
Electroless Plating of Pla and Petg for 3D Printed Flexible Substrates
Authors: Bernasconi Roberto , Natale Gabriele , Levi Marinella , Magagnin Luca
Published: February 2020

The FDM (fused deposition modelling) 3D printing technology has acquired increasing commercial importance in the last few years. Large scale manufactured devices are nowadays available at low cost and are able to reach performances similar to industrial prototyping machines. Considering this recent new technological evolution, the surface finishing researcher is invited to develop and optimize treatments suitable for tridimensional complex objects made with different polymeric materials. One of the most used polymers for FDM printing is PLA (polylactic acid) due to its dimensional stabily after cooling, a condition needed to avoid deformations during the printing process. PLA presents other desirable properties like biodegradability and good mechanical properties, as well as remarkable disadvantages like poor resistance to aggressive environments and low glass transition temperature. Recently PLA is being replaced in many 3D printing processes by PETG (polyethylene terephthalate glycol-modified), a polymer able to compensate the drawbacks of PLA (with the only main disadvantage of being not biodegradable). An important surface treatment that the objects printed with these two polymers may require is metallization, a process able to make conductive the surface and to give new functional and aesthetic properties to the polymer. Metallization of non-conductive materials can be achieved using techniques like PVD, but one of the most economical is electroless plating.

Starting from this consideration, the present work aims at testing the possibility of electroless NiP and Cu plating on PLA and PETG. The resulting films can be used as deposited or as adhesion layers for the deposition of other metals like decorative chromium. A convenient preparation of the surface must be performed in order to achieve good uniformity and cohesion with the polymeric substrate. Two etching processes, alkaline and acidic, are used to increase the roughness of the surface and permit a good adhesion of the electroless plated metals. The characterization of the pretreatment is therefore presented together with the activation process and the description of the properties of the coatings obtained. To conclude the work and to provide a future perspective the deposition on 3D printed prototypes is performed.
(Invited) Solution-Processing Routes to Conductive Ultrathin Films of Ruthenium Dioxide...on Any Substrate
Authors: Rolison Debra R. , Pala Irina R. , Donakowski Martin D. , Chervin Christopher N. , Long Jeffrey W. , Stroud Rhonda , Brintlinger Todd , Liu Xiao
Published: February 2020

The deposition of continuous, ultrathin, conductive films from liquid-phase is still a rare processing outcome. We have demonstrated that RuO2 can be deposited from chilled, nonaqueous solutions of RuO4 as an ~10 nm–thick film on planar substrates using a scalable, atom-efficient, self-limiting synthetic protocol [1]. The versatility of this protocol is exemplified in that deposition ensues on any type of substrate—metal, semiconductor, ceramic, polymer, or salt—or whether the substrate is planar, curved, or non-line-of-sight [1–3]. The resulting air- and water-stable conductive oxide, even though nanoscopic, is electrically conductive and broadband transparent over an uncommonly wide range for an oxide—from UV to microwave—far surpassing the spectral window of indium-doped tin oxide (ITO) [1]. Recently, we were able to isolate square centimeters of self-supporting, ultrathin RuO2 films, by releasing them from soluble substrates. The freestanding films are also conductive and transparent, exhibiting unexpected mechanical flexibility and strength. They can then be manipulated and further characterized by being placed on holders (i.e., TEM grids) or devices (i.e. nanofabricated stages for mechanical or thermal transport measurements). We will provide an overview of the synthetic methods and the characterization of this ultrathin, disordered material, including optical, structural, thermal and mechanical properties.

[1]   D.R. Rolison, J.W. Long, C.N. Chervin, J.C. Lytle, and K.A. Pettigrew, U.S. Patent #8,889,257; J.W. Long, J.C. Owrutsky, C.N. Chervin, D.R. Rolison, J.S. Melinger, U.S. Patent, issued 9-Dec-2014.

[2]   C.N. Chervin, A.M. Lubers, K.A. Pettigrew, J.W. Long, M.A. Westgate, J.J. Fontanella, D.R. Rolison, Nano Lett.
9 (2009) 2316–2321.

[3]  C.P. Rhodes, J.W. Long, K.A. Pettigrew, R.M. Stroud, and D.R. Rolison, Nanoscale
3 (2011) 1731–1740.
Additive Effects on Surface Dynamics and Growth at the Metal-Electrolyte Interface
Authors: Magnussen Olaf M.
Published: February 2020

Understanding of electrodeposition on nanometer length scales becomes more and more important, especially in the context of microchip metallization. Although additives are indispensable for modern plating technology, the molecular scale mechanisms by which they modify growth processes at the solid-liquid interface are often unclear. In this talk I will discuss fundamental studies by state-of the-art in situ scanning probe microscopy and synchrotron-based X-ray scattering techniques, focusing on the effect of chloride adsorbates and simple organic surfactants on Au and Cu electrodeposition. These methods allow direct quantitative measurements of the surface dynamics and interaction of chemisorbed species as well as time-resolved operando studies of the structural evolution of the deposit during growth. In particular, these studies reveal that the surface transport processes and the resulting deposit morphology are strongly affected by the potential and coadsorbates, leading to pronounced and partially unexpected growth behavior.
In Situ Vibrational Spectroscopy of Electrode Interfaces
Authors: Baldelli Steven
Published: February 2020

In situ sum frequency generation (SFG) vibrational spectroscopy is used to study the alkanethiolate monolayer on metal electrodes.  The electrode potential is swept from the double layer region toward the cathodic limits in basic electrolyte solution and the reductive desorption process is observed.  Correlations in the cathodic current and SFG spectra are made to help elucidate details of the monolayer film under the desorption process.  SFG spectroscopy of the monolayer reveals feature that could not easily be deduced by ex situ analysis.
In Situ Scanning Tunneling Microscopy Imaging Self-Assembled Monolayers of Mercaptoacetic Acid and Cupric Ion on Au(111) Electrode
Authors: Yau Shuehlin
Published: February 2020

We employed voltammetry and scanning tunneling microscopy (STM) to study the coadsorption of mercaptoacetic acid (MAA) and cupric ions (Cu2+) on Au(111) electrode from 0.5 M sulfuric acid + 0.8 M CuSO4 + 0.03 mM MAA. Irreversibly adsorbed Cu2+ ions were reduced at 0.27 V first then at -0.2 V (vs. Ag/AgCl), ascribed to the underpotential and overpotential deposition processes, respectively. Counting the amount of charge involved in the stripping peak of the Cu deposit rendered quantification of Cu2+ ions codeposited with MAA on the Au(111) electrode, which yielded roughly 7.7 x 1014 Cu2+ ions/cm2. MAA alone and MAA + Cu2+ were adsorbed in Au(111) - (3 x r13) and (p x r3) structures, respectively. Cu2+ could be imaged by the STM, but their high mobility made it difficult to obtain high – quality STM results needed to quantify the amount of adsorbed Cu2+. Spatial structures of MAA molecules segregated onto the Cu deposit were found to vary with potential. They returned to the Au(111) electrode once the Cu deposit was oxidized at E > 0.4 V, yielding MAA + Cu2+ structures different from those seen at the pristine sample.

Figure 1
Superconformal Film Growth: Insights Provided By Seiras
Authors: Moffat Thomas P. , Liu Guokun , Zou Shouzhong , Ou Yang Liang-Yueh , Josell Daniel , Lee Chang Hwa , Richter Lee
Published: February 2020

State of the art manufacturing of semiconductor devices involves electrodeposition of copper for device wiring and more recently for through-silicon-vias (TSVs). The process depends on the use of electrolyte additives that affect the local deposition rate thereby resulting in superconformal, or bottom–up “superfilling” of trenches and vias. In the case of Damascene processing of submicron features the deposition process is explained by the recently developed curvature enhanced accelerator coverage (CEAC) mechanism. The model stipulates that 1.) the growth velocity is proportional to the local accelerator, or catalyst, surface coverage and 2.) the catalyst remains segregated at the metal/electrolyte interface during copper deposition. For growth on non-planar geometries this leads to enrichment of the catalyst on advancing concave surfaces and dilution on advancing convex sections; thereby giving rise to bottom-up superfilling of recessed surface features such as trenches and vias. In the case of larger features other avenues for feature filling become available that will be outlined in some detail. Despite the success of these superconformal growth processes much remains to be known concerning the detailed molecular nature of the competitive co-adsorption processes involved in both the suppression and acceleration of the metal deposition reaction. The application of in situ surface science tools such as in situ STM and SEIRAS towards a better understanding of the additive interactions will also be detailed. The interaction between adsorbed anions, polyether suppressors, sulfonate terminated thiol/disulfide accelerator additves and water at the growing interface reveal the critical role of hydrophobic/hydrophilic interactions in controlling the growth velocity during metal deposition. The talk will conclude with an overview of the current understanding of additive adsorption, consumption and/or deactivation dynamics relevant to superfilling and microstructural evolution in both Damascene and TSV Cu processing.
Texture Evolution during Zinc Electrodeposition
Authors: Orme Christine , Keist Jayme , Wright Paul K , Evans Jim W
Published: February 2020

This talk investigates the impact of additives and ionic liquids on the stability of zinc interfaces by measuring the temporal evolution of the surface roughness. Experiments are designed to quantify the morphological evolution during charge and discharge cycles in battery electrolytes. We use of in situ electrochemical atomic force microscopy and in situ ultra-small angle x-ray scattering (EC USAXS) to track surface morphology during zinc electrodeposition from two electrolytes: alkaline potassium hydroxide and an ionic liquid, 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate (BMIM OTF). Images are used to quantify the temporal evolution of lateral correlations and surface roughness as a function of deposition thickness.

 Zinc growth within BMIM OTF displays a surface morphology that has not been described for zinc before; the surface organizes into domains of parallel platelets with the prism facets perpendicular to the surface. Because of this textured morphology, the surface roughness stops growing under some conditions. This cessation of roughening is counter to current models of surface evolution. The coarsening of the grains and the evolution of the roughness are quantitatively described using scaling exponents.  The goal of our project is to link early time nucleation events with the onset of large-scale instabilities such as dendrites.

 Auspices: Portions of this work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Additives for Suppressing Zinc Dendrites in Rechargeable Zinc Metal Batteries
Authors: Banik Stephen J , Akolkar Rohan
Published: February 2020

Rechargeable zinc-based battery systems hold great promise for future energy storage devices due to their low cost and high theoretical energy density.1 However, the development of portable or stationary rechargeable zinc batteries has been hindered by several critical issues. The key issue has been the evolution of dendritic zinc electrodeposit morphology during battery charging,2,3leading to battery capacity fade and cell shorting.

In this work, we focus on the use of organic electrolyte additives to suppress zinc dendrite growth. We examine both acidic and alkaline electrolytes, which are relevant to acidic zinc-halogen flow batteries and alkaline zinc-metal batteries, respectively. To study zinc dendrite propagation, we employ in-situ microscopy during growth of the electrodeposit.4 To study the mechanism by which organic additives modulate the dendrite propagation rate, we utilize classical polarization measurements on a rotating disc electrode. For acidic zinc electrolytes, we studied numerous additives (Figure 1) and their dendrite suppression efficacy. We observed that strongly polarizing additives suppress zinc dendrites more than weak polarizers. For zinc electrodeposition from an alkaline electrolyte, we identified that polyethylenimine (PEI) enables near-complete dendrite suppression,5even at low concentrations (~50 ppm, see Figure 2). Figure 2 also shows electrochemical polarization measurements on a rotating disk electrode, which confirm the polarizing effect of the PEI.

The aforementioned characterization techniques, together with electrochemical quartz crystal microgravimetry, ex-situscanning electron microscopy, and various ‘additive-injection’ tests, provide insights into the mechanism by which additives suppress dendritic growth of zinc. Additives are believed to adsorb onto the zinc surface and suppress zinc electrodeposition kinetics locally, thereby inhibiting activation-controlled dendrite propagation. In the talk, we will develop the mechanistic understanding further and provide guidelines for judicious selection of the additive chemistry for dendrite-free zinc electrodeposition in acidic and alkaline systems. 

References:

[1]: Y. Li and H. Dai, Chem. Soc. Rev., 43, 5143 (2014).

[2]: K. Wang, P. Pei, Z. Ma, H. Xu, P. Li, X. Wang, J. Power Sources, 271, 65 (2014).

[3]: C. P. de Leon, A. Frias-Ferrer, J. Gonzalez-Garcia, D. A. Szanto, and F. C. Walsh, J. Power Sources, 160, 716 (2006).

[4]: S. J. Banik and R. Akolkar, J. Electrochem. Soc., 160, D519 (2013).

[5]: S. J. Banik and R. Akolkar, Manuscript submitted to Electrochimica Acta, October 2014.

Figure 1
Effect of Additive on the Formation of Cusn Alloy Nano-Trees Formed with DC Electroplating
Authors: Shingubara Shoso , Shimizu Tomohiro , Kaneko Naoto , Tada Yoshihiro
Published: February 2020

We have found nano-tree of CuSn alloy by DC electroplating with a constant potential mode. The plating bath contained copper-sulphate, tin-nitrate, citric acid, and additive (PEG). Substrate was Pt thin film sputtered on a Si substrate.  Nano-trees have many branches which separate from trunk perpendicularly, and sub-branches grow perpendicular from them also.   The electroplating condition to grow nano-tree structure is limited in the very narrow window of cathode potential. From TEM-EDS analysis, it was clarified that each branch of nano-tree is single crystal having orthorhombic structure.  Diameter of branch distributes between a few tens of nm to a few hundreds of nm. 

   There is a significant effect of additive (PEG) for the formation of nano tree structure as shown in Fig.1. If there is no addition of PEG,  deposited Cu-Sn alloy has a round rock shape only (Fig.1-a). However, when adequate amount of PEG is added to the plating bath, a very interesting nano-tree structure grows almost perpendicularly to the substrate (Fig.1-b). The top view of the nano-tree clearly shows branches are formed with 4-fold symmetry.   

   Nano-tree has a huge ratio of surface area to its volume, and is regarded as a typical three-dimensional nano-porous structure.  The nano-tree may have a high potential to be used for electrode of Li-ion batteries, as well as chemical sensors when it is oxidized.

Further studies are in progress to clarify the effect of the additive for the growth of nano-tree structure.   

Figure 1
Gravitational Level Effects on Coupling Phenomena Between Morphological Variations of Electrodeposited Film of ZnO and Mass Transfer Rates
Authors: Osaki Hiroshi , Wakatsuki Takao , Homma Takayuki , Fukunaka Yasuhiro
Published: February 2020

Coupling Phenomena between morphological or microstructural evolution rate of electrodeposited film and mass transfer rates must be well understood in order to tailor the unique physical properties of nanostructured films. It is well known microstructure of electrodeposited ZnO film is drastically influenced by the adsorption phenomena of surfactant molecule.  However, the mass transfer rate of surfactant has been seldom discussed, especially when natural convection accompanying oxide layer synthesis reaction is induced in an electrolytic cell. The surfactant concentration is significantly influenced at the liquid/soli. interface. Now it is discussed how gravitational level influences the nucleation and growth phenomena of electrodeposited ZnO.

     ZnO electrodeposition onto FTO/ITO substrate is firstly performed in 0.1MZn(NO3)2-LiNO3 aqueous solution (pH=5.1) at 70°C without addition of surfactant molecule. The substrates were ultrasonically cleaned sequentially in acetone, ethanol and deionized water for 15 min., respectively. The counter electrode was a sheer of pure zinc (Nilaco Corp.). Effective surface of workin and counter electrodes were 10x10mm. They were embedded in each side of channel walls.  Ag/AgCl was used as a reference electrode. The cell was arranged in two different configurations: (1) a horizontally installed cathode facing downward over a horizontal anode (C/A) and (2) an anode over a cathode (A/C). No natural convection is principally expected under the former configuration.

     Current transients were measured at various electrode potential. No apparent differences were observed between -0.85 and -0.8V. Below -0.9V, they were categorized into four stages.

Stage 1: Double layer charging and start of NO3
-reduction

Stage 2: Induction time for nucleation

Stage 3: ZnO nucleation and growth

Stage 4: Transport limited

     The initial three stages can be described by a model including progressive nucleation and kinetically controlled 3D growth. Surface OH- concentration during the nucleation period was estimated by using a simple model. We assume ZnO nucleation can be caused by the production of precursor like Zn(OH)4
2-. Surface morphology and XRD spectrum are changed by the gravitational field direction. The effect may be attributed to natural convection, eventually, concentration of reactant near the substrate cathode surface during electrodeposition.
Microvia Filling in an Acidic Copper Planting Bath with Insoluble Anodes
Authors: LIU CHU-CHI , Dow Wei-Ping
Published: February 2020

Microvia filling of a printed circuit board (PCB) by acidic copper electroplating has been widely used in electronic industry. The filling mode of copper electrodeposition in microvia must be bottom-up form. Moreover, bottom-up filling phenomenon is believed to be related to the properties and interaction of plating additives. Especially, the interaction of three (accelerator, suppressor, leveler) components have significantly effect on copper filling performance. It was confirmed that soluble anodes (i.e., P-doped Cu anode) have disadvantage when they were used in the acidic copper plating bath. For instance, the shape of the soluble anodes are changeable with operating time, which may causes non-uniform current distribution to form unequal copper thickness on substrate. Therefore, a special functional insoluble anode was used to replace the soluble anode and conventional dimensionally stable anode (DSA) to maintain better bath stability. The disadvantage of soluble anode can be improved by using the novel DSA. In this work, a planting formula which was composed of chloride ions, suppressor (polyethylene glycol), leveler (quaternary ammonium species) and a novel accelerator instead of bis(3-sulfopropyl) disulfide (SPS). SPS is not appropriate for DSA system because of easy breakdown; therefore, we develop a novel accelerator, ACC, which has a longer lifetime and better performance for acceleration on copper deposition than SPS. Using DSA instead of P-doped Cu anode has another important contribution, that is, SPS reacts with the copper anode to produce Cu(I)-thiolate. The Cu(I)-thiolate is a strong accelerator in the presence of chloride ion. Cu(I)-thiolate will be accumulated in the copper plating bath to destroy the synergy between the suppressor and accelerator. DSA has no this issue because DSA has no copper. Herein, we will show that ACC combining with DSA can perform excellent copper fill in microvia.
Modeling of Growth and Morphology in Synthesis of Nanoparticles and Nanostructures
Authors: Privman Vladimir , Gorshkov Vyacheslav
Published: February 2020

We describe a recently developed kinetic Monte Carlo approach that can describe shape selection and morphologies obtained in solution/suspension synthesis of "isomeric" (even-proportioned) crystalline nanoparticles. This approach also allows the study of the kinetics of the emergence of nanostructures involving matter uptake and exchange. The latter include core-shell particle formation, particle sintering, and on-surface nanostructure growth.

Figure 1
Screen-Printed Silver Source-Drain Electrodes for a Solution-Processed Zinc-Tin-Oxide Thin-Film Transistor
Authors: Kwack Young-Jin , Choi Woon-Seop
Published: February 2020

As a first step to achieve all-printing-processed oxide thin film transistors (TFTs), we prepared solution-processed zinc-tin oxide (ZTO) TFTs by screen printing electrodes for the first time. The source and drain were silver nanoparticles, and the channel length was patterned by using screen printing technology. Different silver nanoinks and process parameters were tested to find optimal source and drain contacts. A finely patterned channel layer of 100 μm in channel length was defined with a 4 μm thickness. The electrical characteristics of solution-processed ZTO with screen-printed source-drain electrodes were comparable to those of solution-processed ZTO with vacuum-deposited electrodes. Relatively good electrical properties of screen-printed solution-processed oxide TFT were obtained: a mobility of 2.3 cm2/V s, an on-off current ratio of 106, a Vth of 17 V and a subthreshold swing of 3.2 V/dec. The bias stability was also characterized.  Because of the microstructure of the device, water and oxygen adsorption from the atmosphere affected the Vth shift and the subthreshold slope change under a gate bias stress.
Electrohydrodynamic (EHD) Jet Technique for Indium-Zinc-Oxide (IZO) Thin-Film Transistors
Authors: Kwack Young-Jin , Choi Woon-Seop , Kim Hunho
Published: February 2020

Many studies have reported that oxide TFTs for printed electronics can be processed using solution methods. Printed electronics can circumvent time consuming-, expensive-, and chemical waste-photolithography process for patterning. One of the issues in solution processed oxide TFTs is that a high temperature annealing process is needed to remove organic residues because they can deteriorate the electrical characteristics. For a low temperature process, many studies have examined a variety ways to reduce the reaction under 200oC but retain excellent performance. Another issue is to apply a printing process for fine patterning. Most studies of solution-processed oxide semiconductors were carried out by spin coating or ink-jet printing. The electrohydrodynamic (EHD)-jet printing process is unique technique that can overcome these limits. In the case of a paste, transpiring is possible by setting a high voltage because inks are forced down by the electric field between the nozzle and substrate. The ink can form a drop to spray configuration under a range of bias voltages.  Electrohydrodynamic (EHD) jet-printed indium- zinc-oxide thin-films transistors (TFTs) were prepared at various annealing temperatures. The EHD jet was achieved by optimizing the process parameters; such as the precursor viscosity, driving voltages, and substrate temperatures. The EHD jet-printed IZO films were characterized using a range of analytical methods. Metal oxide formation was confirmed by X-ray photoelectron spectroscopy. The EHD jet-printed IZO TFTs showed good electrical properties: mobility of 4.8 cm2/Vs, threshold voltage of 8.4 V, on-to-off current ratio of 107, and a subthreshold slope of 1.2 V/dec at 400oC. The positive and negative bias stability were also analyzed.