Multilayer Edge Molecular Devices Based on Plasma Oxidation of Photolithographically Defined Bottom Metal Electrode

TL;DR

This paper presents a simplified method for fabricating multilayer edge molecular devices using plasma oxidation of a tantalum electrode to create ultrathin insulators, enabling efficient molecular conduction and novel electronic behaviors.

Contribution

It introduces a one-step oxidation process to grow ultrathin tantalum oxide insulators directly on bottom electrodes, simplifying MEMED fabrication and enhancing device performance.

Findings

OMCs bridged across TaOx improve conduction symmetry

Transient current suppression observed in TaOx tunnel junctions

Ultrathin TaOx insulators enable efficient molecular channels

Abstract

A multilayer edge molecular electronics device (MEMED), which utilize the two metal electrodes of a metal-insulator-metal tunnel junction as the two electrical leads to molecular channels, can overcome the long standing fabrication challenges for developing futuristic molecular devices. However, producing ultrathin insulator is the most challenging step in MEMED fabrication. A simplified molecular device approach was developed by avoiding the need of depositing a new materiel on the bottom electrode for growing ultrathin insulator. This paper discuss the approach for MEMED's insulator growth by one-step oxidation of a tantalum (Ta) bottom electrode, in the pholithographically defined region; i.e. ultrathin tantalum oxide (TaOx) insulator was grown by oxidizing bottom metal electrode itself. Organometallic molecular clusters (OMCs) were bridged across 1-3 nm TaOx along the perimeter of a tunnel junction to establish the highly efficient molecular conduction channels. OMC transformed the asymmetric transport profile of TaOx based tunnel junction into symmetric one. A TaOx based tunnel junction with top ferromagnetic (NiFe) electrode exhibited the transient current suppression by several orders. Further studies will be needed to strengthen the current suppression phenomenon, and to realize the full potential of TaOx based multilayer edge molecular spintronics devices.