Write and erase

Nano Lett. http://doi.org/c4vw (2019)

Two-dimensional (2D) and ferroelectric materials can be used in contact to create devices like field-effect transistors (FETs) or switchable tunnel junctions, where a polarization inversion of the ferroelectric changes the conductance of an adjacent 2D material. Now, Lipatov et al. combine these two types of devices to produce a programmable FET. The conductance of a MoS₂ monolayer is reversibly tuned by imprinting one or more well-defined conductance channels into the ferroelectric layer underneath.

Credit: American Chemical Society

The device consists of a flake of monolayer MoS₂ on a ferroelectric Pb(Zr,Ti)O₃ (PZT) layer (pictured). Two electrodes on top of the MoS₂ act as source and drain. The polarization of the PZT layer determines the conductivity of the MoS₂ and, hence, the FET state. The source–drain current depends on the number of channels with high conductance that connect the two electrodes. Through the use of voltage pulses applied with the conductive tip of a scanning probe microscope (SPM) through the MoS₂, the researchers can imprint and erase areas of low resistance (R). While the overall conductance change is not extraordinarily high, the ability to write, erase and rewrite one, two or more channels — and the possibility of connecting several electrodes via flexible channels — makes this approach interesting for its memristive functionalities and, though a little speculative at this stage, for artificial synapsis application.