Out-of-plane interface dipoles and anti-hysteresis in graphene-strontium titanate hybrid transistor

Anindita Sahoo,Tathagata Paul,Arunesh Roy,Arindam Ghosh,Roald Ruiter,Tamalika Banerjee,Maxim Mostovoy,Dhani Nafday,Tanusri Saha-Dasgupta

doi:10.1038/s41699-018-0055-5

Abstract

The out-of-plane electric polarization at the surface of SrTiO3 (STO), an archetypal perovskite oxide, may stabilize new electronic states and/or host novel device functionality. This is particularly significant in proximity to atomically thin membranes, such as graphene, although a quantitative understanding of the polarization across graphene–STO interface remains experimentally elusive. Here, we report direct observation and measurement of a large intrinsic out-of-plane polarization at the interface of single-layer graphene and TiO2-terminated STO (100) crystal. Using a unique temperature dependence of anti-hysteretic gate-transfer characteristics in dual-gated graphene-on-STO field-effect transistors, we estimate the polarization to be as large as ≈12 μC cm−2, which is also supported by the density functional theory calculations and low-frequency noise measurements. The anti-hysteretic transfer characteristics is quantitatively shown to arise from an interplay of band bending at the STO surface and electrostatic potential due to interface polarization, which may be a generic feature in hybrid electronic devices from two-dimensional materials and perovskite oxides.

Highlights

The rich and diverse phenomenology of perovskite oxides,[1,2,3,4] which includes electronic and structural phase transitions, colossal magnetoresistance to ferroelectricity and superconductivity, holds great promise for new concepts in device technology and material engineering
While the transfer characteristics using hexagonal boron nitride (hBN) top gate shows no hysteresis, that using STO back gate becomes strongly anti-hysteretic at low temperature (≲200 K), which is quantitatively associated with in-built electric polarization at the graphene–STO
We have developed a phenomenological model for anti-hysteretic transfer characteristics using band reconstruction and electrostatic potential at the STO surface, which may be applicable to graphene field-effect transistors (FETs) on other polarized substrates as well

Summary

Introduction

The rich and diverse phenomenology of perovskite oxides,[1,2,3,4] which includes electronic and structural phase transitions, colossal magnetoresistance to ferroelectricity and superconductivity, holds great promise for new concepts in device technology and material engineering. While the transfer characteristics using hBN top gate shows no hysteresis, that using STO back gate becomes strongly anti-hysteretic at low temperature (≲200 K), which is quantitatively associated with in-built electric polarization at the graphene–STO

Results

Conclusion