Molecular Memory with Atomically-Smooth Graphene Contacts

TL;DR

This paper demonstrates the use of bilayer graphene as an atomically-smooth contact in molecular memory devices, enabling stable WORM memory with high resistance states and excellent retention.

Contribution

It introduces bilayer graphene as a novel atomically-smooth contact material for nanoscale molecular memory devices, improving stability and retention.

Findings

Devices exhibit irreversible switching to high-resistance state at 0.8-1.2 V

Memory ratio between low and high resistance states is 20-40

Graphene contact prevents electromigration and improves device stability

Abstract

We report the use of bilayer graphene as an atomically-smooth contact for nanoscale devices. A two-terminal Bucky ball (C60) based molecular memory is fabricated with bilayer graphene as a contact on the polycrystalline nickel electrode. Graphene provides an atomically-smooth covering over an otherwise rough metal surface. The use of graphene additionally prohibits the electromigration of nickel atoms into the C60 layer. The devices exhibit a low-resistance state in the first sweep cycle and irreversibly switch to a high resistance state at 0.8-1.2 V bias. The reverse sweep has a hysteresis behavior as well. In the subsequent cycles, the devices retain the high-resistance state, thus making it write-once read-many memory (WORM). The ratio of current in low-resistance to high-resistance state is lying in 20-40 range for various devices with excellent retention characteristics. Control sample without the bilayer graphene shows random hysteresis and switching.