Quantum Dot FET Ligand Removal and Inorganic Matrix Deposition

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Solution Overview

Problem

Quantum dot field-effect transistors (QD FETs) suffer from a bias-stress effect, where electrical characteristics change over time due to charge trapping, leading to unstable currents and preventing practical applications, as existing solutions fail to eliminate this issue effectively.

Innovation Solution

Exposing quantum dots in QD FETs to substances like H2S or H2O to remove or modify ligands, followed by depositing an infilling material such as metal oxides or sulfides to reduce or eliminate bias-stress effects, thereby stabilizing the device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If quantum dots are used in FETs, then carrier mobility is improved, but bias-stress effect causes current instability

Engineering Contradiction:

Improvecarrier mobilityVSAvoidcurrent stability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent removes ligands from the quantum dot surface through exposure to substances like H2S or H2O, extracting the harmful component (ligands that cause charge trapping) while preserving the quantum dot's core functionality and high carrier mobility

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent deposits an inorganic matrix (such as metal oxides or sulfides) over the quantum dots, creating a composite structure that combines the high carrier mobility of quantum dots with the stability of the inorganic matrix, thereby eliminating bias-stress effects

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If ligands are present on quantum dot surface, then quantum dots are stable, but charge trapping and ion motion cause bias-stress effect

Engineering Contradiction:

Improvequantum dot stabilityVSAvoidbias-stress effect

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent selectively removes ligands from the quantum dot surface through chemical exposure, extracting the harmful charge-trapping component while maintaining the structural integrity of the quantum dot through subsequent inorganic matrix deposition

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the surface chemistry parameters of the quantum dots by replacing organic ligands with inorganic matrix materials, transforming the surface properties to eliminate charge trapping while preserving quantum dot stability

Inventive Principle:

Principle #35Parameter changes

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 method achieves stable currents with high carrier mobility and indefinite environmental stability, eliminating bias-stress effects and enhancing the practicality of QD FETs for applications like displays and optoelectronics.

Implementation Method 1

exposing at least one quantum dot in a QD FET to a substance, wherein the substance is configured to modify a surface of the at least one quantum dot to reduce charge trapping and/or ion motion

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 2

depositing an infilling material over the surface of the at least one quantum dot

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Data Source

PatentUS10224422B2Method to fabricate quantum dot field-effect transistors without bias-stress effect

Publication Date: 2019.03.05 RGT UNIV OF CALIFORNIA

AI summary

Disclosed herein are embodiments of a method to form quantum dot field-effect transistors (QD FETs) having little to no bias-stress effect. Bias-stress effect can be reduced or eliminated through, as an example, the use of a gas or liquid to remove ligands and/or reduce charge trapping on the QD FETs, followed by deposition of an inorganic or organic matrix around the QDs in the FET.