440
12 Localized or Spatially Selective Electrodeposition Methods
side of the observation window. Therefore, the area to which the electron beam is
focused determines the reaction zone, allowing a locally selective deposition without
patterning the substrate itself. The in situ obtained image refers to the wall side of the
species forming, while the solution side can be imaged ex situ after opening the liquid
microcell. The major conclusion of the above-mentioned studies was that a threshold
charge is necessary to initiate the growth of Pt by using the electron beam for the
reduction of the Pt(IV) precursor. The preliminary step before the Pt deposition itself
was a beam-induced modification of the substrate surface. Since the reaction zone
was confined to the irradiated area, the feature size of the nanostructures produced
depended only on the focusing condition of the electron beam, which could lead to
25 nm dot sizes in the best case [57, 58].
The electron beam can induce the reduction of metal ions where nanoparticles are
present in the solution. In this case, the typical growth mode is the formation of a
shell on the already existing particles, as it was shown for the case of Pd deposition
in the presence of Au nanoparticles [59]. The great advantage of the in situ TEM
observation of nanoparticle-seeded growth is that the impact of the electron beam can
be well separated from the impact of the particles itself. It was found that the growth
rate of particles decreases with their distance from the illuminated area, indicating
that the transport of the beam-induced reactive particles (most likely the hydrated
electrons) is a rate-determining step in the shell formation around the nanoparticles.
Depending on the nanoparticle size, the morphology of the external deposit changes
from a compact shell to dendrite-decorated external layers as the size of the Au
nanoparticle increased.
12.3 Deposition at the Liquid–Liquid Interface
12.3.1 Basic Overview of the Appropriate Systems
This book follows the classification of electrochemical nanostructure formation
processes on the basis of the configuration of the phases involved and the structure of various elements of the electrochemical cell, in particular the substrate, and
secondarily on the energetics of the deposition process. Another means of the classification of electrodeposition processes is to take into account the consistency of
the phases involved in the process. From this point of view, the possible pairs are
solid–solid, solid–liquid, liquid–liquid, solid–gas and liquid–gas. The treatment of
the deposition systems in accord with the phases involved can be read in another
review [60]. The list above enumerates the phases involved on the basis of their
density, mentioning the phase with higher density first; however, this is different
from the classification where the emphasis is on the charge carrier. For instance,
in plasma processes (that will be discussed later in Chap. 14), the gaseous phase
is a mixed conductor with a high electron conductivity. It is just shortly mentioned
12 Localized or Spatially Selective Electrodeposition Methods
side of the observation window. Therefore, the area to which the electron beam is
focused determines the reaction zone, allowing a locally selective deposition without
patterning the substrate itself. The in situ obtained image refers to the wall side of the
species forming, while the solution side can be imaged ex situ after opening the liquid
microcell. The major conclusion of the above-mentioned studies was that a threshold
charge is necessary to initiate the growth of Pt by using the electron beam for the
reduction of the Pt(IV) precursor. The preliminary step before the Pt deposition itself
was a beam-induced modification of the substrate surface. Since the reaction zone
was confined to the irradiated area, the feature size of the nanostructures produced
depended only on the focusing condition of the electron beam, which could lead to
25 nm dot sizes in the best case [57, 58].
The electron beam can induce the reduction of metal ions where nanoparticles are
present in the solution. In this case, the typical growth mode is the formation of a
shell on the already existing particles, as it was shown for the case of Pd deposition
in the presence of Au nanoparticles [59]. The great advantage of the in situ TEM
observation of nanoparticle-seeded growth is that the impact of the electron beam can
be well separated from the impact of the particles itself. It was found that the growth
rate of particles decreases with their distance from the illuminated area, indicating
that the transport of the beam-induced reactive particles (most likely the hydrated
electrons) is a rate-determining step in the shell formation around the nanoparticles.
Depending on the nanoparticle size, the morphology of the external deposit changes
from a compact shell to dendrite-decorated external layers as the size of the Au
nanoparticle increased.
12.3 Deposition at the Liquid–Liquid Interface
12.3.1 Basic Overview of the Appropriate Systems
This book follows the classification of electrochemical nanostructure formation
processes on the basis of the configuration of the phases involved and the structure of various elements of the electrochemical cell, in particular the substrate, and
secondarily on the energetics of the deposition process. Another means of the classification of electrodeposition processes is to take into account the consistency of
the phases involved in the process. From this point of view, the possible pairs are
solid–solid, solid–liquid, liquid–liquid, solid–gas and liquid–gas. The treatment of
the deposition systems in accord with the phases involved can be read in another
review [60]. The list above enumerates the phases involved on the basis of their
density, mentioning the phase with higher density first; however, this is different
from the classification where the emphasis is on the charge carrier. For instance,
in plasma processes (that will be discussed later in Chap. 14), the gaseous phase
is a mixed conductor with a high electron conductivity. It is just shortly mentioned