Inter-grain coupling effects on Coulomb oscillations in dual-gated nanocrystalline silicon point-contact transistors

Inter-grain electron-coupling effects are investigated at 4.2 K in dual-gated, point-contact, single-electron transistors fabricated in nanocrystalline silicon. The nanocrystalline silicon film is ∼40 nm thick, with grains ∼10-30 nm in size. The point-contact transistor channel is ∼30 nm×30 nm×40 nm in size, with two side-gates. Only a few grains exist within the channel and different grains contribute in varying degrees to the device conduction. By modifying the inter-grain coupling using selective oxidation of the grain boundaries, both electrostatic and wavefunction-coupling effects can be observed in the Coulomb oscillations vs. the two gate voltages.