Page 4 - Molecules for Charge-Based Information Storage

Molecules for Charge-Based Information Storage Lindsey and Bocian

FIGURE 3. Multistate molecular architectures.
the linker on an outer ligand, and the overall orientation of was accommodated first by alcohols, 14,16,20,2427,32,41,46,47
the dyad in a nonvertical fashion. 12,19 thiols, 20,27,32,45 and selenols 20,27,32,40 and later by all-car-
The tether portion of the molecular architecture serves bon tethers. 29,3335,38,4146,48,49 A selection of tethers is
multiple functions: (1) attach the redox-active molecule to shown in Figure 5. A surprising variety of all-carbon tethers
the surface, (2) orient the molecule with respect to the were successfully attached to Si.
surface, and (3) perhaps provide a conduit for electrical
communication. The tether includes a linker and a surface Characterization and Optimization of Prop-
attachment group. Initially, we employed thiols as the sur- erties of Molecules on Surfaces
face attachment group so as to attach the molecules to a Au Understanding the properties of the porphyrin monolayers
surface. 38,1113,15,1820,23,30,36,37,45 The resulting self-as- on surfaces is essential for utilizing these molecular archi-
sembled monolayers on Au are readily characterized in tectures in viable electronic components. Accordingly, the
laboratory studies; however, Au cannot be used inside properties of the various monolayers on surfaces were
chips owing to the facile diffusion of Au atoms in Si-based investigated in detail. These studies addressed issues includ-
semiconductors under the conditions employed for fabri- ing monolayer stability/robustness, 25 surface binding/ad-
cation. The need for attachment to industry-compatible sorption geometry, 30,32,33,35,37,45 electron-transfer
surfaces such as oxides (e.g., SiO 2 ,WO 2 ) was met with rates, 15,16,32,33,35,50,51 andcharge-retentiontimes. 3,11,13,14,32,33,35
phosphonates, 17,21,22,28,31 whereas attachment to Si itself Each of these characteristics in turn reflects a key feature of

Vol. 44, No. 8 ’ 2011 ’ 638–650 ’ ACCOUNTS OF CHEMICAL RESEARCH ’ 641