Critical Behavior in Au Nanoparticle Arrays: Implications for All-Metal Field Effect Transistors with Ultra-high Gain at Room Temperature

The working principle of large-area, open-gate field effect transistors (ogFETs) is attractive for the high-sensitivity detection of chemicals and interfacing with single cells. We describe an ogFET composed of a self-assembled, two-dimensional (2D) random network of 1D chains of 10 nm Au particles spanning over 25 μm. The device has a gating gain of 103-fold at room temperature (RT) compared to <50% for reported nanoparticle arrays at RT. The current, I ∼(V - VT)ζ, is functionally identical to the Coulomb blockade (CB) effect observed at cryogenic temperatures, and the conductance gap, VT, at room temperature cannot be attributed to local charging for large particles (>5 nm). Surprisingly, unlike the effect observed in CB, the VT remains invariant over a large gating potential 0-25 V, leading to a universal behavior where all the I-V curves collapse into a single master curve. We explain the universality as a classical critical behavior by quantitatively mapping the percolation path in real-space images. The paths evolve as self-similar percolation channels in a fractal dimension of 1.88. The device principle enables a 103-fold gating gain in all-metallic nanoparticle arrays at RT and will potentially lead to ogFET sensors and electrochemical devices with liquid-gate junctions. The critical behavior with bias may serve as a model system to study the electronic transport in these exotic systems.