On-chip atomristors

Abstract

Resistive random access memories (RRAM) have shown interesting electrical performance and are relatively easy to fabricate, but their use is still restricted to a few applications due to limited reliability. The microelectronics industry has explored the fabrication of RRAM devices, but only a few amorphous metal-oxides have been tested on-chip, which are mainly TaO_X, HfO₂, Al₂O₃, Cu_XO, SiO₂, ZrO₂ and NiO. However, in these materials controlling accurately resistive switching through defect generation/recombination is very challenging because the positions of the atoms and the strengths of their bonds are unknown. Here we explore the use of defect-free monolayer hexagonal boron nitride (hBN) as insulating film in RRAM devices — often referred to as atomristors. In this crystalline material the number of atoms is 36.97 nm⁻², they are arranged in-plane in a hexagonal lattice with covalent bonding, and the minimum energy to form a defect is 7.43 eV. This lower amount of uncertainties and the absence of local defects allows us to better adjust the electrical stresses to be applied for write, erase and read events, resulting in highly-reproducible non-volatile bipolar resistive switching (on-chip) with high endurance up to millions of cycles in multiple devices. These results represent a very significant advancement compared to previous atomristors patterned on SiO₂ substrates. Unlike in previous atomristors, the switching is not produced by native defects, but it is produced by field-driven defects, which exhibit high potential for device ultra-miniaturization.