Insights into nonvolatile resistive switching in monolayer hexagonal boron nitride

A recent demonstration of nonvolatile resistive switching in monolayer hexagonal boron nitride (h-BN) has paved the way for the development of the thinnest memory devices feasible. Nevertheless, the exact mechanism of such remarkable resistive switching has remained obscure, which may hinder the optimization of such attractive technology. Here, we present the first dynamic description of the resistive switching process in a Ni/monolayer h-BN/Ni device at an atomistic level by employing reactive molecular dynamics simulations. We show that with the application of a suitable bias, the h-BN layer moves vertically and peels off Ni ions from the electrode, which gets adsorbed in the N vacancy center. From density-functional-theory based electron-localization-function calculations, we confirm that N vacancy generates highly delocalized electrons around the vacancy location resulting in the adsorption of Ni ions, though such a phenomenon is not likely in case of B vacancy due to the absence of electronic states around the defect center. We demonstrate the restoration of Ni ions with the application of reverse bias in case of bipolar switching, and by rising temperature in case of unipolar switching, which agrees with the experimental observations. Finally, we conduct ab initio quantum transport calculation to find an increase in zero-bias conductivity of about 7.4 times after the Ni ion adsorption. This atomistic insight enables precise defect-engineering in 2D materials for the realization of h-BN based high-performance memristive crossbar array.