Acceleration effect of thiourea on the oxidation reaction of hypophosphite ion on Ni surface

Kunimoto, Masahiro; Endo, Kazuaki; Nakai, Hiromi; Homma, Takayuki

doi:10.1016/j.electacta.2012.09.070

Cited by 12 publications

(13 citation statements)

References 28 publications

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“…Figure 9 shows results obtained by plotting time dependence of current without the addition of thiourea, (a), addition of thiourea to the bath containing hypophosphite ion without Ni ion after 500 s, (b), or the bath containing Ni ion without hypophosphite ion, (c). 24 Among these profiles, the current density increased most prominently when thiourea was added to the bath containing hypophosphite ion, which support the calculated results described above. The …”

Section: Theoretical Analysis On the Reaction Mechanism Ofsupporting

confidence: 77%

“…Figure 6 shows the model describing the co-adsorption of thiourea and hypophosphite ion on the Ni surface, and Table 2 shows the calculated results of adsorption energy for hypophosphite ion. 24 From this result, the presence of thiourea enhanced the adsorption step of hypophosphite ion. On the other hand, thiourea did not exhibit any clear effect on the dehydrogenation (P-H bond breaking) and oxidation (OH ¹ coordination) steps, 24 as is shown in Fig.…”

Section: Theoretical Analysis On the Reaction Mechanism Ofmentioning

confidence: 86%

“…24 From this result, the presence of thiourea enhanced the adsorption step of hypophosphite ion. On the other hand, thiourea did not exhibit any clear effect on the dehydrogenation (P-H bond breaking) and oxidation (OH ¹ coordination) steps, 24 as is shown in Fig. 7.…”

Section: Theoretical Analysis On the Reaction Mechanism Ofmentioning

confidence: 86%

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Electrochemical Processes for the Fabrication of Functional Micro–nano Structures and Devices: Mechanistic Understanding and Process Development

Homma

2015

Electrochemistry

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Electrochemical approaches for the fabrication of functional micro-nano structures and devices were comprehensively described primarily on the basis of the results obtained from previous studies conducted by the author's group with the aim of demonstrating the potential for achieving further precise controllability. First, a theoretical study was conducted for investigating the processes, mainly focusing upon electroless deposition to present an approach for analyzing its reaction mechanism from the molecular level. These approaches could be powerful tools for elucidating the overall process and could contribute toward achieving the precise design of processes. Second, some experimental approaches for achieving the precise control of micro-nano fabrication of functional structures, such as maskless and electroless fabrication of metal nano-patterns, lateral enhanced electrodeposition to form ultrathin layers, as well as the nanostructures for various devices by through-mask electrochemical deposition, were introduced to demonstrate high capability of the processes for nanoscale fabrication in various applications.

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Section: Theoretical Analysis On the Reaction Mechanism Ofsupporting

confidence: 77%

Section: Theoretical Analysis On the Reaction Mechanism Ofmentioning

confidence: 86%

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Electrochemical Processes for the Fabrication of Functional Micro–nano Structures and Devices: Mechanistic Understanding and Process Development

Homma

2015

Electrochemistry

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“…[16][17][18] All calculations were performed by DFT with Gaussian 09. 19 The exchange-correlation function was B3LYP, the basis set for H and Cl was 6-31+G * * , 20,21 and the basis set for Si was LANL 2DZ dp ECP.…”

mentioning

confidence: 99%

Analysis of Cathodic Reaction Process of SiCl₄during Si Electrodeposition in Ionic Liquids

Tsuyuki

Fujimura

Kunimoto

et al. 2017

J. Electrochem. Soc.

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Elementary steps in the electrochemical reduction process of SiCl 4 in trimethyl-n-hexylammonium bis(trifluoromethylsulfonyl) imide (TMHATFSI) was investigated, focusing on molecular level behavior of the reactants at solid-liquid interface. Electrochemical measurements using an electrochemical quartz crystal microbalance (EQCM) identified a reduction peak corresponding to Si electrodeposition and several elementary steps with stable intermediates forming prior to the deposition. For detailed analysis, X-ray reflectivity (XRR) measurements with synchrotron radiation were applied in situ. The change in reflectivity of the electrode surface during the deposition was found to be due to the formation of a polymer-like Si such as Si 2 Cl 6 , which is an intermediate layer during the deposition process. These results were theoretically supported by density functional theory (DFT) calculations: after an electron transfers from the electrode, the Si in SiCl 4 forms the bond with another SiCl 4 , rather than the Si of the substrate, resulting in the formation of the intermediate structure. These data suggest an elementary step in the SiCl 4 reduction process which can be described as follows; when SiCl 4 is reduced, a polymer-like Si form such as Si 2 Cl 6 is generated. This intermediate species further reacts with other Si reactants after receiving additional electrons, which then finally deposits as Si on the substrate.

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“…[15][16][17][18] Therefore, in this study, a mechanism for the acceleration and suppression effect of thiourea on electroless Ni deposition is proposed based upon the Raman spectroscopy analysis and density functional theory (DFT) calculations. While the sulfur atom dissociated from thiourea should also play an important role on the effects, 19 molecular thiourea is considered to be primarily important, as shown in our previous study; 11 this study attempts to analyze the influence of the molecular thiourea adsorbed on the Ni surface. Since our previous study has demonstrated that thiourea predominantly affects the anodic reaction as described above, moreover, this study focused on the effects on the hypophosphite ions reaction.…”

mentioning

confidence: 97%

Effect of Thiourea on Oxidation of Hypophosphite Ions on Ni Surface Investigated by Raman Spectroscopy and DFT Calculation

Jiang

Kunimoto

Yanagisawa

et al. 2013

J. Electrochem. Soc.

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Thiourea is well known and widely used additive for controlling the rate of electroless Ni deposition, and it is known to show complicated behavior in acidic/alkaline electroless deposition baths. To understand this, several experiments and theoretical calculations were performed. In the experiments, the adsorption of thiourea and the reducing agent (i.e., hypophosphite ions) on a Ni surface was characterized with a high-selectivity component at a right angle down to the sub-monolayer level using surface-enhanced Raman spectroscopy. By comparing the results with those obtained from the theoretical calculation, co-adsorption of thiourea and hypophosphite ions on the Ni surface was confirmed. Moreover, the acceleration or suppression effects of thiourea on the oxidation of hypophosphite ions on a Ni surface in acidic/alkaline bath were analyzed from the experimental and computational perspectives. Accordingly, an explanation that unifies both the acceleration and suppression mechanisms of thiourea in terms of its own fundamental characteristics is proposed; this will be one of the most important processes for industrial applications of electroless Ni deposition.

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Acceleration effect of thiourea on the oxidation reaction of hypophosphite ion on Ni surface

Cited by 12 publications

References 28 publications

Electrochemical Processes for the Fabrication of Functional Micro–nano Structures and Devices: Mechanistic Understanding and Process Development

Electrochemical Processes for the Fabrication of Functional Micro–nano Structures and Devices: Mechanistic Understanding and Process Development

Analysis of Cathodic Reaction Process of SiCl₄during Si Electrodeposition in Ionic Liquids

Effect of Thiourea on Oxidation of Hypophosphite Ions on Ni Surface Investigated by Raman Spectroscopy and DFT Calculation

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Acceleration effect of thiourea on the oxidation reaction of hypophosphite ion on Ni surface

Cited by 12 publications

References 28 publications

Electrochemical Processes for the Fabrication of Functional Micro&ndash;nano Structures and Devices: Mechanistic Understanding and Process Development

Electrochemical Processes for the Fabrication of Functional Micro&ndash;nano Structures and Devices: Mechanistic Understanding and Process Development

Analysis of Cathodic Reaction Process of SiCl4during Si Electrodeposition in Ionic Liquids

Effect of Thiourea on Oxidation of Hypophosphite Ions on Ni Surface Investigated by Raman Spectroscopy and DFT Calculation

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Product

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Electrochemical Processes for the Fabrication of Functional Micro–nano Structures and Devices: Mechanistic Understanding and Process Development

Electrochemical Processes for the Fabrication of Functional Micro–nano Structures and Devices: Mechanistic Understanding and Process Development

Analysis of Cathodic Reaction Process of SiCl₄during Si Electrodeposition in Ionic Liquids