Information Technology Reference
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platforms for breakthrough solutions in view of the continuously increasing
demand for increased storage capacity performances [2].
The introduction of physical switching properties into molecules is a genuine
task of chemical design, while the realization of molecular 2D arrangement relies
on default of top-down construction principles within the lower nanometer regime
and on bottom-up approaches such as supramolecular self-assembly techniques.
Single molecule addressing and switching will take advantage of cutting-edge
scanning probe and other techniques provided by physicists. In this way,
nanoscale molecular information storage represents an archetypical example for
the need of cross-border research.
Cutting edge research in the lower nanometer regime may be suspicious of
scientific discoveries at the fundamental level of knowledge because the research
deals with the investigation of physical phenomena close to their intrinsic
correlation lengths. Within this respect, we will discuss in the following four
candidates of ''more-than-Moore'' strategies, standing for technologies that
exceed the conventional state-of-the-art technological scheme [3]. The following
perspectives are discussed: the gloaming of nonbinaric logics by using ion
dots instead of the larger quantum dots [4, 5]; the use of molecules within
the cellular automata scheme [6], propositions for molecular quantum compu-
ting concepts [7]; and the impact of surface-confined self-assembly schemes. All
four concepts materialize structurally in specific 2D arrangements, called metal
ion assemblies (MIAs) and networks (MINs), which represent the platform for
the alternative computation approaches. Finally, the self-assembly of carbon
nanotubes (CNTs) and their use as interface between nanoscopic molecular
devices and macroscopic environment will be reviewed.
12.1.2. The Ion Dot Concept
By analogy to semiconductor quantum dots [8], a metal ion coordinated by
organic ligands can be considered as a natural quantum dot, i.e., the artificial
atom is replaced by a real one (Fig. 12.1). Typically, the feature size of a single
quantum dot is at the very lower limit, around 10 nm. However, most are
much larger. So called ion dots, defined as single metal ion centers surrounded
by their organic ligands, are at least more than one order of magnitude smaller in
size [4]. Whereas the electronic level structure of a semiconductor quantum dot is
merely controlled by its geometry, the electronic levels of a coordinated metal ion
are tailored through the type and the geometrical arrangement of its organic
ligands.
The local distribution of electron density around the respective metal ion can
be used effectively as the structural and functional base for the design of
nanoscaled molecular devices. Consequently, the genuine redox, electronic, or
spin states of metal ions and their explicit variability (beyond the two-level
scheme) will set the base for novel kinds of multistate (meaning beyond binary
logics) digital information storage and processing concepts [10].
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