Silicon Nanogap Electrode Engineering for Organic Monolayer Field Effect Transistors*

The fabrication and characterization of planar silicon nanogap electrode structures is described in which contact separation ≥ 30 nm was achieved. Starting from highly doped silicon-on-insulator substrates, fabrication is based on precise control of electron-beam lithography and subsequent reactive ion etching (etch rate 3.6 nm/s). A monolayer of an aromatic organophosphonate is then assembled in the etched nanogap. Conductance is greatly improved compared to a device absent the monolayer, and distinct field-effect induced modulation of the conductance is observed. Finite element simulations of the electrostatic potential distribution of the device structure supports its suitability as a three-terminal field effect device.