Silicon-Immobilized Ferrocenyl Monolayers for All-Solid Molecular Charge Storage and Logic

Monday, May 12, 2014: 11:00
Floridian Ballroom E, Lobby Level (Hilton Orlando Bonnet Creek)
B. Fabre (Université de Rennes 1), H. Zuilhof (Wageningen University), P. Hapiot (Université de Rennes 1), S. Pujari (Wageningen University), L. Scheres (Surfix B. V.), and Y. Li (Wageningen University)
The functionalization of technologically relevant conducting surfaces, such as oxide-free, hydrogen-terminated silicon (H-Si), with high-quality ferrocene (Fc) [1] and metal-complexed porphyrin [2] -terminated monolayers has been demonstrated to be a powerful bottom-up approach for the fabrication of electrically addressable charge-storage devices with low-power consumption.

Compared with metalloporphyrins, Fc is a much smaller molecule (average diameter of tetraphenylporphyrin and Fc are about 18 and 6.6 Å, respectively), and consequently is immobilized on silicon with a higher surface coverage, which gives rise to higher charge densities. Indeed, the surface coverages reached for high-quality ferrocenyl monolayers are in the range of (2.0–5.0) ×10-10 mol cm-2. This does not only allow for an extremely fast electron communication between the electroactive groups [3], but also yields charge densities in the range of 20–50 mC cm-2. These values are thus much higher than those measured for Si/SiO2 capacitors currently used in Dynamic Random Access Memories (5–10 mC cm-2).

Very recently, we also demonstrated that tailor-made micrometer-sized patterns of such redox-active monolayers could behave as light-activated molecular memory cells operating at low voltages with unprecedented capacitance performances [4]. The characteristics of this stimuli-responsive device are of great scientific interest for data-processing applications, such as redox-based Boolean logic gates [5]. In our system, the switching of the capacitance upon light irradiation that is observed only at a certain electrical potential constitutes the principle of all-solid two-input AND logic gate without the need of chemical inputs in solution. Such performances can be ascribed to the judicious combination between a photoswitchable conducting/insulating silicon substrate and high-quality microstamped redox-active assemblies.

[1] Fabre, B. Acc. Chem. Res. 2010, 43, 1509–1518.

[2] Lindsey, J. S.; Bocian, D. F. Acc. Chem. Res. 2011, 44, 638–650.

[3] a) Hauquier, F.; Ghilane, J.; Fabre, B.; Hapiot, P. J. Am. Chem. Soc. 2008, 130, 2748–2749. b) Zigah, D.; Herrier, C.; Scheres, L.; Giesbers, M.; Fabre, B.; Hapiot, P.; Zuilhof, H. Angew. Chem. Int. Ed. 2010, 49, 3157–3160.

[4] Fabre, B.; Li, Y.; Scheres, L.; Pujari, S. P.; Zuilhof, H. Angew. Chem. Int. Ed. 2013, 52, 12024-12027.

[5] de Ruiter, G.; van der Boom, M. E. Acc. Chem. Res. 2011, 44, 563–573.