Ferroelectric semiconductor junctions based on graphene/In2Se3/graphene van der Waals heterostructures

Shihong Xie,Kaiyou Wang,Oleg Kolosov,Eli G Castanon,Nilanthy Balakrishnan,Oleg Makarovsky,Wenjing Yan,Zakhar R Kudrynskyi,Amalia Patanè,Zakhar D Kovalyuk,Anubhab Dey

doi:10.1088/2053-1583/ac1ada

Abstract

The miniaturization of ferroelectric devices offers prospects for non-volatile memories, low-power electrical switches and emerging technologies beyond existing Si-based integrated circuits. An emerging class of ferroelectrics is based on van der Waals (vdW) two-dimensional materials with potential for nano-ferroelectrics. Here, we report on ferroelectric semiconductor junctions (FSJs) in which the ferroelectric vdW semiconductor α-In2Se3 is embedded between two single-layer graphene electrodes. In these two-terminal devices, the ferroelectric polarization of the nanometre-thick In2Se3 layer modulates the transmission of electrons across the graphene/In2Se3 interface, leading to memristive effects that are controlled by applied voltages and/or by light. The underlying mechanisms of conduction are examined over a range of temperatures and under light excitation revealing thermionic injection, tunnelling and trap-assisted transport. These findings are relevant to future developments of FSJs whose geometry is well suited to miniaturization and low-power electronics, offering opportunities to expand functionalities of ferroelectrics by design of the vdW heterostructure.

Highlights

Since the pioneering studies in the 1920s by Joseph Valasek on ferroelectricity in Rochelle salt (e.g. KNaC4H4O6·4H2O) [1], ferroelectric materials have had an enormous impact in science and exploited in many technologies ranging from high-energy capacitors and transducers to ultrasound medical imaging [2,3,4]
ferroelectric semiconductor junctions (FSJs) For our studies we focus on the α-phase of In2Se3, which is ferroelectric at room temperature with a Curie temperature Tc above 500 K [18]
The preliminary characterization of the α-In2Se3 crystals by x-ray diffraction, piezoresponse force microscopy (PFM), Raman and photoluminescence (PL) spectroscopy is in the Methods section and in figures S1 and S2 of supplementary material S1

Summary

Introduction

Since the pioneering studies in the 1920s by Joseph Valasek on ferroelectricity in Rochelle salt (e.g. KNaC4H4O6·4H2O) [1], ferroelectric materials have had an enormous impact in science and exploited in many technologies ranging from high-energy capacitors and transducers to ultrasound medical imaging [2,3,4]. In the FSJ, the polarization of the nanometrethick In2Se3 layer is controlled by a voltage applied between two graphene electrodes, modifying the Schottky-like barrier at the graphene/In2Se3 interface [15, 20]: the change in the height of the barrier modulates the transmission of electrons across the interface, leading to memristive effects. We show that this is a robust process over a wide range of temperatures, below and above room temperature. It can be modified by a relatively small applied voltage (∼1 V) and by light: the free carriers generated by light and/or thermionic injection can neutralize the polarization charges at the graphene/α-In2Se3 interface and influence the hysteretic behaviour in the electrical transport, offering opportunities for future developments

Results and discussion

Conclusions

Conflict of interest