Biomedical Engineering Reference
In-Depth Information
Figure 1.2
The electrochemical and chemical method to synthesize the
quantum dots and other semiconductor nanocrystals on graphite.
The first step involves the electrodeposition of metal
nanoparticles onto a graphite surface from a solution containing
the corresponding metal ions. The metal nanoparticles are
electrochemically oxidized to yield a metal oxide (MO), in which
the oxidation state of the metal matches the oxidation state in the
final product. Finally metal oxide nanoparticles are converted into
nanoparticles of a semiconducting salt (MX) via a displacement
reaction in which oxide or hydroxide is replaced by the desired
anions (X). Examples of using these methods can be shown in the
synthesis of CuI [15], CdS [16], and ZnO [17] quantum dots. Ultrathin
films of quantum dots with deposits of nonconnected nanocrystals
and thick films of more than 10 nm in average thickness can be made
by electrochemical methods [18-20]Besides quantum dots, several
methods and variations have been developed to electrodeposit other
semiconducting nanocompounds. Oxides are probably the largest
group of electrodeposited compounds (e.g., aluminum anodization).
The electrodeposition of II-VI compounds has been extensively
studied in a number of articles [21-23]. Various semiconductor
electrodeposition methods were also reviewed [24,25]. In summary,
the most prominent electrodeposition methods for semiconducting
compounds include: codeposition, precipitation, and various two-
stage techniques.
Semiconductor film can be electrodeposited either by EC-
ALE or by codeposition [26]. The most successful methodology to
form II-VI compounds has been codeposition [27-31], where both
elements are deposited at the same time from the same solution.
Stoichiometry is maintained by having the more inactive element
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