Low-Temperature Molecular Vapor Deposition of Ultrathin Metal Oxide Dielectric for Low-Voltage Vertical Organic Field Effect Transistors

We demonstrate a low-temperature layer-by-layer formation of a metal-oxide-only (AlO_<i>x</i>) gate dielectric to attain low-voltage operation of a self-assembly based vertical organic field effect transistor (VOFET). The AlO_<i>x</i> deposition method results in uniform films characterized by high quality dielectric properties. Pin-hole free ultrathin layers with thicknesses ranging between 1.2 and 24 nm feature bulk dielectric permittivity, ε_AlO<i>x</i>, of 8.2, high breakdownfield (>8 MV cm^–1), low leakage currents (<10^–7A cm^–2 at 3MV cm^–1), and high capacitance (up to 1 μF cm^–2). We show the benefits of the tunable surface properties of the oxide-only dielectric utilized here, in facilitating the subsequent nanostructuring steps required to realize the VOFET patterned source electrode. Optimal wetting properties enable the directional block-copolymer based self-assembly patterning, as well as the formation of robust and continuous ultrathin metallic films. Supported by computer modeling, the vertical architecture and the methods demonstrated here offer a simple, low-cost, and free of expensive lithography route for the realization of low-voltage (<i>V</i>_GS/DS ≤ 3 V), low-power, and potentially high-frequency large-area electronics