The Nanocell: A Chemically Assembled Molecular ... - IEEE Xplore

SEMINARIO et al.: NANOCELL: CHEMICALLY ASSEMBLED MOLECULAR ELECTRONIC CIRCUIT 1621Fig. 7. Single molecule and corresponding I–V characteristics for (a) single molecule featuring NDR and (b) two NDR molecules in series configuration; thissimplest configuration of a combined molecular circuit features multivalued characteristics that are used for programmability. (c) Combination of three of thesedevices already shows characteristics not observed in any other bulk device; the level of programmability can be further controlled by a third gate. This complexityincreases until we get to addressable circuits connected to microelectronic interfaces, as the one shown in Fig. 6 [3], [4], [12], [17], [28], [104]–[106], [110], [111].Fig. 8.Possible bottom-up approach to the fabrication of a nanocell IC on a top-down substrate.Fig. 7 [3], [4], [12], [17], [28], [104]–[106], [110]. The singledevice shows a nonlinear I–V behavior, which is an NDR.If two of these devices are connected in series, the resultantI–V for the series circuits shows multivalued responses, asindicated in Fig. 7(b). For some bias voltages, the currentthrough the series circuit can have two different and welldefinedvalues. Thus, the programmability feature of moleculeshaving nonlinear I–V characteristics allows compensating forthe lack of addressability in molecular circuits. The burdenof fabrication is now passed into the programming of thenanocell; fortunately, some progress has been already done inthis respect [8]. In general, the molecular pattern inside thenanocell is unique; thus, no two cells would be constructed withthe same molecular conformation even when they are requiredto perform the same functions. Choosing the correct moleculesand the correct arrangement for the nanocell strongly helps toreduce the burden of programming them. Eventually, depositiontechniques and molecular synthesis will improve, such thata nonrandom fabrication of the nanocell can be approached.Fig. 8 shows a possible, at least for the present time, hierarchicalassembly of molecular systems. Molecules, clusters, nanotubes,etc., are prepared by standard chemical synthesis techniques,