The layer of Co-based precursor on the substrate surfaces was reduced
to Co(0) by dipping in 0.26 M NaBH4+0.25 M NaOH (denoted
as a borohydride solution) at 25 or 46 °C for 5 min.
The copper plating bath used for electroless metallization was the
Shipley® CIRCUPOSIT 3350 copper plating solution, containing formaldehyde
as a reducing agent and operating at a temperature of 43–
50 °C. In our experiments electroless copper deposition was carried
out at 46 °C for 2 min.
Analytical grade chemicals were used to prepare solutions.
The microgravimetric studies were performed with a microbalance
QCM922 (Princeton Applied Research, USA), two digital voltmeters B7-
46/1 connected to a PC through the GPIB-USB-2 cable, a programmingpotentiostat PI-50-1 and a sweep generator PR-8 (Russia). AT-cut quartz
crystals of 6 MHz frequency (from Intellemetrics Ltd., UK) sputtered by
gold from both sides were used. A standard three-electrode configurationwas
employedwith one side of the quartz crystal, as aworking electrode,
an Ag/AgCl/KClsat electrode as reference, and a Pt-wire as a counter
electrode. The geometric area of the working electrode was 0.636 cm2.
Elemental analysis of deposits was studied by X-ray photoelectron
spectroscopy. The XPS analysis was performed by using an “ESCALAB
MK II” spectrometer (VG Scientific, UK) equipped with a Mg Kα X-ray
radiation source (1253.6 eV) operated at 280W and at a fixed pass
energy of 20 eV. The pressure of 1.33×10−7 Pa was kept in the
UHV analysis chamber. The XPS spectra were recorded for Co2p3/2,
O1s and Cu2p3/2. The sensitivity factors of these elements were
taken from [20]. The spectra obtained were compared with the standard
ones [21–23].
The surface morphology and composition of the samples were examined
using a Scanning Electron Microscope EVO-50 EP (Carl Zeiss
SMT AG, Germany) with Energy Dispersive and Wave dispersion Xray
Spectrometers (Oxford, UK).