Rewritable non-volatile stress information memory by bulk trap-induced giant piezoresistance effect in individual PbS micro/nanowires

Piezoresistance, induced by an applied mechanical stress, has been widely used in various sensors. Herein, individual PbS micro/nanowire-based devices were constructed on flexible insulating plastic substrates. They not only show dynamic strain-evoked giant piezoresistance (GPR) effects, but also show excellent functions for application in non-volatile piezoresistance random access memory (PRRAM). The trapped electron hopping mechanism, tuned by exerting external strain and an electric field, is proposed. Under dynamic compression/tension with a strain of ±0.26%, the gauge factor can approach four orders of magnitude, dominantly originating from the strain-induced variation of the trap barrier height within the PbS micro/nanowires. After loading both compressive and tensile strains at a low operation bias voltage, additionally, the emptying of trap states results in a down-shift of the PbS Fermi level, and correspondingly the device resistivity increases, indicating that the stress-related data can be written/set by loading different strains. Subsequently, the emptied trap states can be filled up under a relatively high external electric field so that in turn the Fermi level of PbS up-shifts, and accordingly the device resistivity restores to the initial low resistance state, that is, the stored stress-related information can be effectively erased/reset by applying a relatively high external bias voltage. The repeatable writing/erasing characteristics of nanostructure-based devices offer an avenue to develop low power and reliable non-volatile PRRAM for applications.