Program Highlights

A Nickelate Channel for a Ferroelectric Field Effect Transistor

Vijay Raj Singh and Xia Hong
Nebraska MRSEC

A field-effect transistor (FET) is a basic building block of modern electronic technology. It consists of a thin-film conducting channel whose in-plane conductivity depends strongly on a voltage applied across an insulating layer adjacent to it, known as the gate. Transistors are used to amplify and switch electronic signals, making them valuable for performing memory and logic operations in modern computers.
An important functional characteristic of a FET is the ON/OFF ratio, defined as the conductivity change between the ON and OFF states controlled by the voltage applied to the gate. Choice of the material for a conducting channel is critical for enhancing the ON/OFF ratio.
One of the possibilities is to exploit properties of the so-called strongly correlated materials where resistance changes dramatically with external stimulus, exhibiting a metal-insulator transition. Among these materials are nickelates, RNiO₃ (where R is a rare earth ion), one of the canonical families of pseudo-cubic perovskites. These materials undergo a metal-insulator transition and may serve as efficient conducting channels in ferroelectric FETs where the switchable polarization of a ferroelectric gate layer modulates the conductivity of the nickelate channel in a non-volatile manner.
Researchers at Nebraska MRSEC employ an epitaxial oxide composite structure consisting of a ferroelectric gate, such as Pb(Zr,Ti)O₃, and a correlated oxide conducting channel, such as (Sm,Nd)NiO₃, as a model system to explore the coupling between the interface electric polarization and conductivity of the nickelate. By applying voltage pulses to the Pb(Zr,Ti)O₃ gate with different polarities, they found induced reversible switching in a 4 nm (Sm,Nd)NiO₃ channel between the low and high resistance states, which can be used to represent the ON and OFF states. This novel field effect device can be used to build high speed, low power electronic devices, such as nonvolatile memories and logic devices.

These programs are supported by the National Science Foundation, Division of Materials Research, Materials Research Science and Engineering Program, Grant 0820521.

Nonvolatile, reversible resistance switching in a 4 nm Sm_0.5Nd_0.5NiO₃ thin film through ferroelectric field effect.