Transistor memory devices with large memory windows, using multi-stacking of densely packed, hydrophobic charge trapping metal nanoparticle array

Organic field-effect transistor (OFET) memories have rapidly evolved from low-cost and flexible electronics with relatively low-memory capacities to memory devices that require high-capacity memory such as smart memory cards or solid-state hard drives. Here, we report the high-capacity OFET memories based on the multilayer stacking of densely packed hydrophobic metal NP layers in place of the traditional transistor memory systems based on a single charge trapping layer. We demonstrated that the memory performances of devices could be significantly enhanced by controlling the adsorption isotherm behavior, multilayer stacking structure and hydrophobicity of the metal NPs. For this study, tetraoctylammonium (TOA)-stabilized Au nanoparticles (TOA-Au_NPs) were consecutively layer-by-layer (LbL) assembled with an amine-functionalized poly(amidoamine) dendrimer (PAD). The formed (PAD/TOA-Au_NP)_n films were used as a multilayer stacked charge trapping layer at the interface between the tunneling dielectric layer and the SiO₂ gate dielectric layer. For a single Au_NP layer (i.e. PAD/TOA-Au_NP)₁) with a number density of 1.82 × 10¹² cm^-2, the memory window of the OFET memory device was measured to be approximately 97 V. The multilayer stacked OFET memory devices prepared with four Au_NP layers exhibited excellent programmable memory properties (i.e. a large memory window (ΔV_th) exceeding 145 V, a fast switching speed (1 μs), a high program/erase (P/E) current ratio (greater than 10⁶) and good electrical reliability) during writing and erasing over a relatively short time scale under an operation voltage of 100 V applied at the gate.