Floating Gate Metal–Oxide–Semiconductor Capacitor Employing Array of High-Density Nanodots Produced by Protein Supramolecule

An array of high-density 1.8×10 12 cm -2 floating nanodots was embedded within a metal–oxide–semiconductor (MOS) capacitor using a cage-shaped protein supramolecule, Listeria ferritin (Lis-fer). A monolayer of Lis-fer with a 4.5 nm ferrihydrite core was adsorbed on a 3 nm tunneling SiO 2 layer on a p-Si substrate by 3-aminopropyl-triethoxysilane (APTES) surface modification. The outer protein was selectively removed and the obtained cores were covered with a 20-nm-thick control SiO 2 layer and an aluminum electrode. The MOS capacitor was annealed in reducing gas (H 2 :N 2 =10:90%), and the embedded cores were reduced to conductive nanodots. The capacitance–voltage characteristics of the MOS capacitor measured at 1 MHz by applying a DC bias voltage from -5 to +5 V showed a clear hysteresis. This result indicates that the array of nanodots produced and positioned by Lis-fer has the ability for electron confinement.