Evaluations and considerations for self-assembled monolayer field-effect transistors

We elucidate the key chemical and physical requirements necessary for the future successful design and fabrication of molecular field-effect devices. We show that the molecular assembly, device fabrication, and electrical measurements of reported self-assembled monolayer field-effect transistors (SAMFETs) cannot be reproduced. Carrier tunneling and device electrostatics place minimum molecular lengths of L > 2.5-3 nm and minimum gate dielectric thickness t(dielectric) less than or equal to L/1.5 for such devices. In conflict with reported SAMFET device characteristics, for the values of L and t(dielectric) in these structures, it is fundamentally impossible to either turn the devices off or to obtain a significant field-effect. Synthesis, assembly, and characterization of functionalized molecular systems and fabrication and characterization of appropriately scaled device structures may enable the successful preparation of a molecular field-effect transistor.