Chemistry Reference
In-Depth Information
Figure 3.5. (a) Schematic drawing of a confined anode. (1) represents the con-
nection with an external electric circuit, (2) the metal deposit, (3) the thin single
crystals and (4) the insulating substrates. (b) SEM images of a thin single crystal of
(BEDT-TTF)Cu
2
(NCS)
3
. The maximum thickness of this crystallite is
c
.10
m.
ยต
Reprinted with permission from Deluzet
et al
., 2002b.
Confined electrocrystallization
When the EC process is forced to occur within two opposite insulating flat sub-
strates the technique is termed CEC and leads to thin single crystals, their thickness
ultimately defined by the separation between both substrates (Thakur
et al.
, 1990).
This technique can be universally applied, as the parent standard EC technique,
to the synthesis of a variety of thin single crystals of conducting and insulating
molecular materials.
As illustrated in Fig. 3.5(a), the spatial confinement is achieved by opposing
two flat insulating substrates, e.g., glass, mica, a thick silicon dioxide layer grown
on a silicon substrate, etc. On one of the substrates a metal film is deposited, e.g.,
gold, which acts as the working electrode during the EC experiment. The two
substrates are mechanically held together and immersed in the electrolyte solution.
The geometry of the confined anode appears to have little effect on the size and
quality of the grown crystals.
In a CEC experiment, there are several salient differences as compared to stan-
dard EC, a prominent one being the duration of the experiment. While a stan-
dard EC experiment can last a few days, it takes typically several weeks for CEC
