Unexpected large electrostatic gating by pyroelectric charge accumulation

TL;DR

This paper demonstrates a novel, long-lasting electrostatic gating method in graphene devices using pyroelectric charge accumulation at a van der Waals interface, revealing a new voltage-free control mechanism.

Contribution

It introduces a new approach to achieve stable, long-term electrostatic gating in graphene via pyroelectric effects at a van der Waals interface, which was previously overlooked.

Findings

High doping concentrations up to 10^13 cm^-2 achieved in graphene.

Pyroelectric charge accumulation causes significant doping without external voltage.

Long-term electrostatic gating enabled by pyroelectric effects.

Abstract

Pyroelectricity refers to the accumulation of charges due to changes in the spontaneous polarization of ferroelectric materials when subjected to temperature variations. Typically, these pyroelectric charges are considered unstable and dissipate quickly through interactions with the external environment. Consequently, the pyroelectric effect has been largely overlooked in ferroelectric field-effect transistors. In this work, we leverage the van der Waals interface of hBN to achieve a substantial and long-term electrostatic gating effect in graphene devices via the pyroelectric properties of a ferroelectric LiNbO3 substrate. Upon cooling, the polarization change in LiNbO3 induces high doping concentrations up to 1013 cm-2 in the adjacent graphene. Through a combination of transport measurements and non-contact techniques, we demonstrate that the pyroelectric charge accumulation, as well as its enhancement in electric fields, are responsible for this unexpectedly high doping level. Our findings introduce a novel mechanism for voltage-free electrostatic gating control with long retention.