Bright nickel film deposited by supercritical carbon dioxide emulsion using additive-free Watts bath

Article abstract of DOI:10.1016/j.electacta.2010.06.037

This paper is aimed on studying film smoothening effect of supercritical carbon dioxide emulsion (Sc-CO₂-E) on nickel film electroplated using an additive-free Watts bath. Morphology of nickel film electroplated with Sc-CO₂-E was found to be similar to that of nickel film prepared from electroless plating. Surface roughness (R_a) of nickel film electroplated with Sc-CO₂-E was lower than that of nickel film electroplated through conventional method. A minimum R_a was found for nickel film electroplated through conventional method and Sc-CO₂-E when increasing current density from 0.010 to 0.150 A/cm². The minimum R_a was 69.8 nm at 0.020 A/cm² and 14.0 nm at 0.030 A/cm², respectively for conventional and Sc-CO₂-E case. After the minimum point, increasing rate of R_a increased was lower for Sc-CO₂-E case; this was because of higher hydrogen solubility in Sc-CO₂. Grain size of nickel film electroplated with Sc-CO ₂-E was found to be finer than that of conventional case.

Full text of DOI:10.1016/j.electacta.2010.06.037

Electrochimica Acta 55 (2010) 6469–6475
Contents lists available at ScienceDirect
Electrochimica Acta
journal homepage: www.elsevier.com/locate/electacta
Bright nickel film deposited by supercritical carbon dioxide emulsion using
additive-free Watts bath
∗
Tso-Fu Mark Chang, Masato Sone , Akinobu Shibata, Chiemi Ishiyama, Yakichi Higo
Precision and Intelligence Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa, 226-8503, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 April 2010
Received in revised form 9 June 2010
Accepted 12 June 2010
Available online 19 June 2010
This paper is aimed on studying film smoothening effect of supercritical carbon dioxide emulsion (Sc-CO2-
E) on nickel film electroplated using an additive-free Watts bath. Morphology of nickel film electroplated
with Sc-CO2-E was found to be similar to that of nickel film prepared from electroless plating. Surface
roughness (Ra) of nickel film electroplated with Sc-CO2-E was lower than that of nickel film electroplated
through conventional method. A minimum Ra was found for nickel film electroplated through conven-
2
tional method and Sc-CO2-E when increasing current density from 0.010 to 0.150 A/cm . The minimum
Keywords:
2
2
Ra was 69.8 nm at 0.020 A/cm and 14.0 nm at 0.030 A/cm , respectively for conventional and Sc-CO2-E
case. After the minimum point, increasing rate of Ra increased was lower for Sc-CO2-E case; this was
because of higher hydrogen solubility in Sc-CO2. Grain size of nickel film electroplated with Sc-CO2-E
was found to be finer than that of conventional case.
Nickel electroplating
Supercritical carbon dioxide emulsion
Additive-free Watts bath
Bright film
©
2010 Elsevier Ltd. All rights reserved.
1
. Introduction
onto the surface of cathode and causes defect on the surface of the
film electroplated.
Supercritical carbon dioxide (Sc-CO ) has received a great
There are many attractive advantages of applying Sc-CO2 in
electroplating reaction, such as low surface tension, adjustable
transport properties, and most importantly, high solubility of
2
attention from industries and academic researches. Sc-CO2 has
properties between those of a gas and a liquid. Physical and trans-
port properties such as density, viscosity, diffusivity, solubility, etc.
of Sc-CO2 can be adjusted through control of pressure and tem-
perature [1]. Sc-CO2 is often used in the extraction process such
as extraction of caffeine and spice in the food industry because of
its ability to dissolve organic substance [2]. Extremely low surface
tension of Sc-CO2 makes it possible to extract solvent out of pores
within nanoarrays and nanoporous structure without damaging
the structure in the drying process [3,4]. In addition, CO2 is not
toxic and inexpensive, which are the advantages of using Sc-CO2.
Electroplating is a key technology for fabricating electronic
devices in integrated circuit industry and micro components of
micro electro mechanical systems. For nickel electroplating, rough-
ness, grain size, hardness and crystal texture of the film can be
controlled by current density, experimental temperature, reaction
time, composition of electrolyte, and usage of additive [5–8]. How-
ever, roughness of the film electroplated is highly dependent on
the roughness of the substrate and addition of organic brightener.
Evolution of hydrogen bubbles is a key problem for electroplating
with aqueous electrolyte [9]. Hydrogen bubbles formed near cath-
ode is an inevitable side reaction, hydrogen bubbles will adsorb
hydrogen in Sc-CO . Desorption of hydrogen bubbles from cathode
2
will be easier in reaction medium containing Sc-CO2 because sol-
ubility of hydrogen in Sc-CO2 is much higher than that in aqueous
solution [1,10]. However, low solubility of metal salts in Sc-CO and
2
low electrical conductivity of Sc-CO2 are limitations in performing
electrochemical reaction with Sc-CO2.
Solubility of metal salts and electrical conductivity of Sc-CO2
can be improved by addition of entrainer [1], or by addition of
surfactant to create an emulsified phase composed of Sc-CO2 and
aqueous electrolyte [11,12]. Roughness and hardness of nickel film
electroplated using brightener-contained electrolyte are found to
be affected by application of supercritical carbon dioxide emulsion
(Sc-CO -E) [13,14]. Experimental temperature, pressure, ratio of
2
CO2 in water (or water in CO ), property and concentration of sur-
2
factant used are found to have influence on the morphology and
properties of nickel film electroplated [15–18].
Roughness of nickel films electroplated with Sc-CO -E using a
2
brightener-contained Watts bath has been found to be smaller than
nickel films electroplated without addition of surfactant and CO at
2
ambient and high pressure [15]. Yan et al. also reported that when
CO2 is substituted by n-hexane for creation of the emulsion, and
surface condition of the nickel film electroplated became worse
with increasing volume fraction of n-hexane in the system [16].
Hexane is known to have similar solvent properties with Sc-CO2,
∗ Corresponding author. Tel.: +81 45 924 5043; fax: +81 45 924 5044.
E-mail address: msone@pi.titech.ac.jp (M. Sone).
0
013-4686/$ – see front matter © 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.electacta.2010.06.037

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T.-F.M. Chang et al. / Electrochimica Acta 55 (2010) 6469–6475
Fig. 1. High pressure apparatus: (a) CO2 gas tank, (b) CO2 liquidization unit, (c)
liquidization pump, (d) high pressure pump, (e) thermal bath, (f) reaction cell, with
PEEK coating on the inner wall, (g) substrates, (h) stirrer, (i) programmable power
supply, (j) back pressure regulator, (k) trap, and (l) thermometer.
Fig. 2. Surface appearance of Ni film: (a) conventional method, (b) conventional
method with 1.0 vol.% surfactant, and (c) electroplated with Sc-CO2-E. Size of the
substrate is 1.0 cm × 2.0 cm.
but transport properties are different between the two solvents. On
the other hand, there is no detailed study on sole effect of Sc-CO -E
2
on film smoothening. Therefore, this study is focused on examining
influence of Sc-CO -E on the properties of nickel film electroplated
2
using an additive-free Watts bath as the electrolyte.
2
. Experimental
2.1. Materials
Carbon dioxide with a minimum purity above 99.9% was pur-
chased from Nippon Tansan Co., Ltd. Additive-free Watts bath
without addition of surfactant was used in the conventional
electroplating. Composition of the additive-free Watts bath was
NiSO ·6H O (300 g/l), NiCl ·6H O (50 g/l), and H BO (50 g/l). For
4
2
2
2
3
4
electroplating with Sc-CO -E, a non-ionic surfactant, polyoxyethy-
2
lene lauryl ether (C12H25(OCH CH )15OH) was added into the
2
2
additive-free Watts bath at a volume fraction of 1.0 vol.% with
respect to the volume of aqueous nickel electrolyte for formation
of the emulsified phase. Copper substrate with width and length at
1
.0 cm × 2.0 cm was used as working substrate at cathode. Nickel
substrate with width and length at 1.0 cm × 2.0 cm was used as
counter electrode at anode.
2.2. Experimental apparatus
The high pressure experimental apparatus (Japan Spectra Com-
pany) used in this study was shown in Fig. 1. The temperature
variation of each run was confirmed to be less than 1.0 K. The maxi-
mum working temperature and maximum pressure were 424 K and
5
3
0 MPa, respectively. The reaction chamber was a stainless steel
16 vessel (PEEK coating on the inner wall) with a volume of 50 ml,
kept in a temperature controlled air bath. There were holes at cham-
ber cap for flow of CO and wiring. Through the holes, plastic coated
2
platinum wires were used to position the substrates and connec-
tion with a programmable power supply. A magnetic agitator with
a cross-shaped magnetic stirrer bar was placed within the reaction
chamber.
2.3. Electroplating
Copper substrates were pre-treated with 10 wt.% NaOH solu-
tion and 10 wt.% HCl solution successively for 1 min and 10 s,
respectively, prior to the electroplating reaction. Distance between
substrates at cathode and anode was kept at 2.0 cm. For conven-
tional electroplating, samples were prepared at ambient pressure
and 323 K. One sample was prepared through conventional method
Fig. 3. AFM 3D results of nickel film electroplated through conventional method:
(a) 0.015 A/cm , (b) 0.030 A/cm , and (c) 0.075 A/cm .
2
2
2

T.-F.M. Chang et al. / Electrochimica Acta 55 (2010) 6469–6475
6471
2
2
2
2
Fig. 4. SEM micrographs of nickel film electroplated through conventional method: (a) 0.015 A/cm , (b) 0.030 A/cm , (c) 0.015 A/cm , and (d) 0.030 A/cm .
with 1.0 vol.% surfactant in the electrolyte to confirm effect of sur-
factant in electroplating reaction, and the sample was electroplated
at 0.010 A/cm for 60 min at 323 K. For electroplating with Sc-CO2-
E, experimental pressure was 15 MPa, and temperature was 323 K.
Both sets of samples were electroplated for 60, 40, 30, 20, 8, and
conventional method with addition of 1.0 vol.% surfactant was very
rough and non-uniform as shown in Fig. 2b. Evolution and adsorp-
tion of many gas bubbles on surface of cathode were observed
with bare-eyes during electroplating process. This was believed to
be the cause of this non-uniform surface. As for nickel film elec-
2
4
0
min at six different current densities, which were 0.010, 0.015,
.020, 0.030, 0.075, and 0.150 A/cm , respectively. Volume ratio of
troplated with Sc-CO -E, the appearance was bright as shown in
Fig. 2c, the brightness was similar to nickel film electroplated with
brightener-contained electrolyte at ambient pressure [5,7].
2
2
aqueous nickel electrolyte in the reaction chamber was 60 vol.%.
Conical shaped structures were found on the surface of nickel
film electroplated through conventional method as shown in AFM
micrographs and SEM micrographs, Figs. 3 and 4, respectively.
This conical shaped structure is a typical way of field-oriented
texture, that is, the preferential growth in the direction of elec-
tric field [19]. By comparing AFM and SEM micrographs of the
nickel film electroplated at different current density, morphol-
ogy of nickel film electroplated through conventional method was
insignificantly affected by change of current density. Large spher-
ical particles with size ca. 20 ␮m were found on the surface. High
magnification SEM micrograph, Fig. 4d showed that surface of the
spherical particle was also covered by conical shaped structures.
On the other hand, surface morphology of nickel film electroplated
2
.4. Analysis
Morphology of the nickel film was examined by a scanning
electron microscope (Fe-SEM, S-4300SE, Hitachi High Technologies
Co., Ltd.) and an atomic force microscope (AFM, XE-100, Park Sys-
tem). Roughness, Ra (arithmetic average of absolute values) was
measured and calculated by AFM in an area of 20 ␮m × 20 ␮m. Ra
equation was given as below:
n
ꢀ
1
Ra = n
|y |where y is the height of peak or depth of trench
i
i=1
and n is the total number of peak and trench
A structural analysis was performed on the nickel film with X-
ray diffraction (XRD, Ultima IV, Rigaku Instrument Co., Ltd.) at a
glancing angle of 1 . The X-ray was generated by a Cu target oper-
ated at 40 kV and 40 mA.
with Sc-CO -E was found to be covered by hemispherical shaped
2
nodular structures as shown in AFM and SEM micrographs, Figs.
5 and 6, respectively. The hemispherical shaped structures were
similar to the morphology of nickel film prepared from electro-
less plating [20,21]. The micrographs showed that morphology
of the nickel film was highly affected by change of current den-
◦
3
. Results
2
sity from 0.015 to 0.030 A/cm . SEM micrographs in Fig. 6 showed
3
.1. Morphology
that the surface became smoother as the amount and size of the
hemispherical structure decreased with increase of current density.
Stripe features were found on nickel film electroplated at current
density of 0.030 A/cm , which was caused by surface features of
copper substrate. Surface features of copper substrate were shown
in Fig. 7.
Surface appearance of nickel film electroplated through conven-
2
tional method was dim as shown in Fig. 2a, which was expected for
nickel film electroplated with additive-free Watts bath at ambient
pressure. Surface appearance of nickel film electroplated through

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T.-F.M. Chang et al. / Electrochimica Acta 55 (2010) 6469–6475
region. A minimum Ra, 14.0 nm was obtained for current density at
2
0
.030 A/cm . Ra of most nickel film electroplated through conven-
tional method and Sc-CO -E were higher than that of the substrate,
2
except at 0.030 A/cm2 for Sc-CO -E case. Ra of the substrate was
2
1
9.8 nm.
3.3. XRD
Major peak in XRD pattern of nickel film electroplated through
conventional method was (1 1 1) peak as shown in Fig. 9, which
was the most preferential crystal growth direction of electroplated
nickel. After normalization the intensities with intensity of the
major peak, intensity of (2 0 0) peak in XRD pattern was found to
increase with increase of current density. Intensity of (2 0 0) peak
increased from 14.4 to 72.1% of the intensity of major peak as cur-
2
rent density increased from 0.015 to 0.150 A/cm . XRD pattern of
nickel film electroplated with Sc-CO -E was shown in Fig. 10, after
2
normalization with the major peak, intensity of (2 0 0) peak was ca.
2
2
0.0% when current density was below 0.075 A/cm . Intensity of
(
2 0 0) peak increased to 30.1% when current density was increased
2
to 0.150 A/cm . Full width at half maximum (FWHM) of the major
peak, which was (1 1 1) peak, of nickel film electroplated with Sc-
CO -E was higher than that of conventional case. Larger FWHM of
2
the major peak in XRD pattern indicated that, grain size of nickel
film electroplated with Sc-CO -E was finer than that of conven-
2
tional case according to Scherrer equation. Scherrer equation was
shown in the following:
ꢁ
average grain size (nm), ꢀ =
ˇ cos ꢂ
where ꢁ is the X-ray wavelength (0.15418 nm), ˇ the FWHM in
radians, and ꢂ is the Bragg angle.
Influence of current density on grain size, calculated using
Scherrer equation, was shown in Fig. 11. Grain size of nickel
film electroplated through both conventional method and Sc-CO2-
E increased as current density increased. For conventional case,
grain size increased from 25.80 nm to 28.66 nm as current density
2
increased from 0.015 to 0.150 A/cm . For Sc-CO -E case, grain size
2
increased from 8.04 to 11.22 nm as current density increased from
2
0
.010 to 0.150 A/cm .
4. Discussion
Film smoothening mechanism of Sc-CO -E is believed to be
2
similar to the mechanism of brightener in electroplating reac-
tion. Brightener is effective in increasing nucleus density of newly
formed nickel nucleus and enhancing hydrogen desorption rate
from surface of cathode, these two factors are found to be important
in increasing smoothness of nickel film electroplated [5]. Electro-
plating is found to have periodic plating characteristic [22], which
is believed to be the reason for grain refinement of nickel film elec-
troplated with Sc-CO -E. Surfactant used in this study is expected
2
2
Fig. 5. AFM 3D results of nickel film electroplated with Sc-CO2-E: (a) 0.015 A/cm ,
2
2
to have influence on increasing brightness of the nickel film elec-
troplated. However, the experimental result, as shown in Fig. 2, has
shown that the surface became worse with only surfactant added
into the electrolyte.
(
b) 0.030 A/cm , and (c) 0.075 A/cm .
3.2. Surface roughness
Influence of current density on roughness, Ra was shown in
4.1. Increase of nucleus density
Fig. 8. For nickel film electroplated through conventional method,
Ra decreased with increase of current density at low current den-
sity region. A minimum Ra, 69.8 nm was obtained when current
density was at 0.020 A/cm . After the minimum point, Ra increased
with increase of current density. Ra of nickel film electroplated
High nucleus density has been found to be a critical factor for
fabrication of bright and smooth nickel film through electrochem-
ical deposition [19]. Increase of nucleus density can be achieved
by reducing the formation energy of new nucleus and increasing
kinetic driving force [5]. Solubility of CO2 in the aqueous elec-
trolyte can be increased at elevated pressure [23]. CO2 dissolved
in the aqueous electrolyte will be in supercritical state. Viscosity
2
with Sc-CO -E at each current density was lower than Ra of con-
2
ventional case. Ra of nickel film electroplated with Sc-CO -E also
2
decreased with increase of current density at low current density

T.-F.M. Chang et al. / Electrochimica Acta 55 (2010) 6469–6475
6473
2
2
2
2
Fig. 6. SEM micrographs of nickel film electroplated with Sc-CO2-E: (a) 0.015 A/cm , (b) 0.030 A/cm , (c) 0.015 A/cm , and (d) 0.030 A/cm .
and surface tension of Sc-CO2 are lower than that of the aque-
ous electrolyte. Therefore, overall viscosity and surface tension of
the reaction medium can be decreased with application of Sc-CO2-
E. Lowering viscosity of the reaction medium can lead to higher
mobility of the reactants in the reaction medium, and this leads to
higher nucleus density. For heterogeneous reaction, such as elec-
troplating reaction, nucleus density can be increased by increasing
wetting area of the aqueous electrolyte on cathode surface.
surface tension of the reaction medium. Although surfactant used
in this study should be effective in reducing wetting area, experi-
mental result has shown that the surfactant itself in the electrolyte
is extremely effective in enhancing adsorption of hydrogen gas bub-
ble on the surface of cathode, which is not beneficial in fabrication
of a bright and smooth surface. Therefore, desorption of hydrogen
gas is a key problem when using this surfactant alone, and wetting
area of the reaction medium can only be increased when CO2 is
Wetting area of the aqueous electrolyte can be increased when a
surfactant is used or reducing overall surface tension of the reaction
also introduced into the system, that is Sc-CO -E. Ra of nickel film
2
2
electroplated with Sc-CO -E at 0.030 A/cm is lower than Ra of cop-
2
medium. Application of Sc-CO -E is effective in lowering overall
per substrate; this is an example of leveling effect caused by high
wetting area of the reaction medium. In addition, reaction rate can
be increased for chemical reaction at high pressure; this can also
contribute to increase of nucleus density.
2
Fig. 8. Current density vs. Ra chart with error bar; dashed line is Ra of copper sub-
strate.
Fig. 7. AFM 3D results of copper substrate.

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T.-F.M. Chang et al. / Electrochimica Acta 55 (2010) 6469–6475
4.2. Restriction of crystal growth
For brightener-contained electrolyte, film smoothening and
grain refinement are achieved by adsorption of the brightener onto
+
surface of cathode, this would lower mobility of Ni and retards
growth of crystal [7]. Mobility of Ni+ is expected to be affected
by application of Sc-CO -E, because of the periodic plating char-
2
acteristic reported by Yoshida et al. [22]. An illustration of periodic
plating characteristic is shown in Fig. 12. In electroplating with Sc-
CO -E, the aqueous electrolyte, non-ionic surfactant and Sc-CO2
2
are in a dynamic emulsified form in the reaction chamber. The
structure of the dispersed phase is similar to reverse micelle, as
shown in Fig. 12a. At the beginning of the reaction, formation of
new nickel nucleus and growth of nickel crystal occur when aque-
ous electrolyte comes in contact with cathode, and crystal growth
stops when Sc-CO2 has contact with cathode, because electrical
conductivity and solubility of metal salts are low in Sc-CO , as
2
Fig. 9. XRD pattern of nickel film electroplated through conventional method.
shown in Fig. 12b. Periodic plating is similar to pulse plating to
some extent [24], where there is a reaction on and off-time. For
“periodic” plating characteristic, the circuit is never entirely turned
off like off-time for pulse plating in a time-scale. However, at some
particular region on surface of cathode where it has contact with
the dispersed phase, the electroplating reaction is stopped. As peri-
odic plating characteristic of the electroplating reaction continued,
surface morphology of the film changes from electric field-oriented
texture, which causes conical shaped structure, to isotropic growth
feature, which forms hemispherical shaped structure as shown in
Fig. 12. As formation of new nickel nucleus and growth of nickel
particles continued, hemispherical shaped nickel particles gradu-
ally cover the entire surface of the substrate to form a smooth film.
This periodical switching between on-time and off-time of the reac-
tion is the reason why grain size of nickel film electroplated with
Sc-CO -E is finer than that of conventional case.
2
Fig. 10. XRD pattern of nickel film electroplated with Sc-CO2-E.
4.3. Enhancement of hydrogen desorption
High solubility of hydrogen in Sc-CO is the most promising part
2
of applying Sc-CO in electroplating reaction [25]. Low surface ten-
2
sion energy and high diffusivity of hydrogen in Sc-CO also promote
2
the tendency for the gas bubbles to mix into the dispersed phase
in Sc-CO -E. Adsorption of hydrogen bubbles on surface of cath-
2
ode can interfere with the electroplating reaction at the particular
region and causes defect or pinhole on the film surface. Because of
the periodic plating characteristic, hydrogen desorption can be fur-
ther promoted when performing electroplating with Sc-CO -E. In
2
pulse plating, film smoothening is achieved when hydrogen bub-
bles desorb at a faster rate when the circuit is switched off. For
electroplating with Sc-CO -E, there is also an off-time because of
2
the periodic plating characteristic. During this off-time, hydrogen
bubble can desorb at a much faster rate compared to conventional
electroplating or pulse plating, because hydrogen bubbles are des-
orbed from surface of cathode by dissolution in Sc-CO2.
Fig. 11. Current density vs. grain size chart.
Fig. 12. Illustration of periodic plating characteristic of electroplating with Sc-CO2-E: (a) new nickel nucleus formed on substrate surface and (b) nickel particle stopped
growing when engulfed by Sc-CO2-E.

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6475
4.4. Current density
nucleus density and hydrogen desorption are believed to be the
reasons for film smoothening and grain refinement of nickel film
In nickel electroplating reaction, increasing current density
electroplated with Sc-CO -E. Ra of nickel film electroplated with
2
is usually effective in reducing grain size. However, the param-
eter affecting grain size is actually cathodic overpotential, and
high current density usually leads to high cathodic overpoten-
tial to give fine crystal grain [6,25]. On the other hand, cathodic
overpotential can also have negative relationship with current
density, where increase of current density causes decrease of
cathodic overpotential and leads to grain coarsening. Decrease of
cathodic overpotential occurs when reaction rate of side reaction
is increased at a much faster rate than the rate of the main reaction
Sc-CO -E is lower than Ra of the substrate when electroplated at
0.030 A/cm . Ra of the nickel film is found to decrease to a min-
imum point with increase of current density. Increase of Ra after
the minimum point is caused by promoted rate of hydrogen evolu-
2
2
tion reaction. Grain size of nickel film electroplated with Sc-CO -E
2
is finer than that of conventional case. Also, grain size is found to
have no direct relationship with Ra of nickel film electroplated.
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the minimum point are lower for electroplating with Sc-CO -E. A
2
minimum Ra found with increase of current density indicates that,
there is no direct relationship between Ra of the film and grain size.
More detailed study on crystal growth orientation and
[18] M.M. Rahman, M. Sone, H. Uchiyama, M. Sakurai, S. Miyata, T. Nagai, Y. Higo,
H. Kameyama, Surface & Coatings Technology 201 (2007) 7513.
[
19] N.S. Qu, D. Zhu, K.C. Chang, W.N. Lei, Surface & Coatings Technology 168 (2003)
23.
[20] H. Watanabe, H. Honma, Journal of Electrochemical Society 144 (1997) 471.
1
microstructure texture of nickel film electroplated with Sc-CO -E
2
[
[
[
21] A.A. Zuleta, O.A. Galvis, J.G. Casta n˜ o, F. Echeverrìa, F.J. Bolivar, M.P. Hierro, F.J.
will be continued in the later study.
Pérez-Trujillo, Surface & Coatings Technology 203 (2009) 3569.
22] H. Yoshida, M. Sone, H. Wakabayashi, H. Yan, K. Abe, X.T. Tao, A. Mizushima, S.
Ichihara, S. Miyata, Thin Solid Films 446 (2004) 194.
23] C.T. Lee, W. Ryoo, P.G. Smith, J. Arellano, D.R. Mitchell, R.J. Lagow, S.E. Webber,
K.P. Johnston, Journal of the American Chemical Society 125 (2003) 3181.
5
. Conclusions
This is the first report on bright nickel film electroplated with
[24] X. Yuan, Y. Wang, D. Sun, H. Yu, Surface & Coatings Technology 202 (2008) 1895.
[
25] J. Ke, W. Su, S.M. Howdle, M.W. George, D. Cook, M. Perdjon-Abel, P.N. Bartlett,
W. Zhang, F. Cheng, W. Levason, G. Reid, J. Hyde, J. Wilson, D.C. Smith, K. Mallik,
P. Sazio, Proceedings of the National Academy of Sciences 106 (2009) 14768.
Sc-CO -E using additive-free Watts bath. The result demonstrated
2
that bright nickel film can be fabricated without usage of brightener
when Sc-CO -E is used. Periodic plating characteristic, enhanced
[26] F. Ebrahimi, Z. Ahmed, Journal of Applied Electrochemistry 33 (2003) 733.
2