Ferroelectric Tunnel Junction With Graphene Contact for High TER

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Solution Overview

Problem

Ferroelectric tunnel junctions face challenges in achieving high tunnelling electroresistance (TER) due to limited barrier height modulation, typically around 0.1 eV in existing junctions based on materials like barium titanate or hafnium dioxide.

Innovation Solution

A ferroelectric tunnel junction structure using layered copper indium thiophosphate (CuInP2S6) as the ferroelectric barrier and monolayer graphene with chromium as asymmetric contacts, inducing a large modulation of average barrier height up to 1 eV through ferroelectric polarization changes, resulting in a TER of above 107.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional ferroelectric materials (barium titanate or hafnium dioxide) are used in tunnel junctions, then the device structure is simple and compatible with existing fabrication processes, but the barrier height modulation is limited to around 0.1 eV, resulting in low tunnelling electroresistance

Engineering Contradiction:

Improvetunnelling electroresistanceVSAvoidjunction structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs a composite structure combining conventional ferroelectric materials with a monolayer graphene contact. This composite approach allows the bulk ferroelectric material to provide stable polarization switching while the graphene interface enables enhanced barrier height modulation through its unique electronic properties, achieving high TER without requiring entirely new material systems

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the electronic parameter (barrier height) by introducing a monolayer graphene contact that modifies the band alignment at the ferroelectric interface. This parameter change transforms the barrier height modulation from the conventional 0.1 eV range to over 1 eV, dramatically improving tunnelling electroresistance while maintaining the same ferroelectric material system

Inventive Principle:

Principle #35Parameter changes

2Reliability

If asymmetric electrodes with monolayer graphene contact are used, then the barrier height modulation increases to over 1 eV achieving high TER, but the manufacturing process becomes more complex requiring precise monolayer fabrication

Engineering Contradiction:

Improvetunnelling electroresistanceVSAvoidfabrication process simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The monolayer graphene acts as an intermediary layer between the metal contact and the ferroelectric material. This intermediary enables the metal to induce large barrier height modulation in the ferroelectric without requiring direct metal-ferroelectric contact, thereby achieving high TER while using standard metal deposition techniques rather than complex monolayer fabrication

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent uses a single layer of graphene that can be transferred and disposed of after serving its function as an interface modifier. This approach avoids the need for complex, expensive, or difficult-to-manufacture components while achieving the desired electronic properties through a simple, transferable monolayer

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The structure achieves a significant enhancement in TER, enabling high-speed, low-power operation with excellent compatibility with silicon CMOS technology and potential for wide-ranging electronic memory and computing applications.

Implementation Method 1

A ferroelectric insulating layer is disposed between the first contact and the second contact and is electrically connected to the first contact and to the second contact. The asymmetric electrodes may cause a large modulation of average barrier height (ABH) when ferroelectric polarization changes direction, exponentially influencing the tunnelling current.

Methodology Applied

Scientific EffectFerroelectric polarization:

Implementation Method 2

The asymmetric electrodes may cause a large modulation of average barrier height (ABH) when ferroelectric polarization changes direction, exponentially influencing the tunnelling current.

Methodology Applied

Scientific EffectTunneling effect:

Data Source

PatentUS20240188303A1Ultrahigh tunneling electroresistance in ferroelectric tunneling junction with giant barrier height modulation by monolayer graphene contact

Publication Date: 2024.06.06 UNIV OF SOUTHERN CALIFORNIA

AI summary

An apparatus for novel high-speed low power non-volatile memory for the next generation electronic memory and computing technology is provided. The apparatus may include a ferroelectric tunnel junction (FTJ) that can switch between two or more conductance states in a reversible and non-volatile manner. A ferroelectric tunnel junction (FTJ) having two electrodes separated by a thin ferroelectric (FE) insulating layer has potential to replace existing volatile and non-volatile memory. Through the application of electrical pulses, the electrical resistance of an FTJ can be reversibly changed in a non-volatile manner by switching the ferroelectric polarization in the ferroelectric insulator layer.