TY - JOUR
T1 - Effect of thiourea on oxidation of hypophosphite ions on Ni surface investigated by raman spectroscopy and DFT calculation
AU - Jiang, Bin
AU - Kunimoto, Masahiro
AU - Yanagisawa, Masahiro
AU - Homma, Takayuki
N1 - Copyright:
Copyright 2013 Elsevier B.V., All rights reserved.
PY - 2013
Y1 - 2013
N2 - 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.
AB - 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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U2 - 10.1149/2.073309jes
DO - 10.1149/2.073309jes
M3 - Article
AN - SCOPUS:84881485826
VL - 160
SP - D366-D371
JO - Journal of the Electrochemical Society
JF - Journal of the Electrochemical Society
SN - 0013-4651
IS - 9
ER -