Field Emission Devices Using Elongate Nanostructures

Solution Overview

Problem

Thermionic emission cathodes in vacuum tube devices require high temperatures, leading to reduced lifetime, warm-up delays, and reliability issues, especially as device size decreases, and they fail to provide the high power capabilities needed for certain microwave systems.

Innovation Solution

The use of elongate nanostructures, such as carbon nanotubes, as field emitters in field emission devices, which operate as cold cathodes, eliminating the need for high-temperature heating and allowing for the creation of nanoscale devices like diodes and triodes with improved power output and reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If thermionic emission cathodes are heated to high temperatures to produce sufficient electron emission current, then electron emission capability is improved, but cathode lifetime is reduced and warm-up delays are introduced

Engineering Contradiction:

Improveelectron emission currentVSAvoidcathode lifetime

Core Design Contradiction:

Use of energy by moving objectVSDuration of action of stationary object

Solution Approach 1:

The patent changes the emission mechanism from thermionic emission requiring high temperature to field emission operating at low temperature. By applying a strong electric field at the cathode surface, electrons are emitted through quantum tunneling without thermal heating, thus achieving sufficient electron emission current while dramatically extending cathode lifetime and eliminating warm-up delays

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the thermal field (heat-based thermionic emission) with an electric field (field emission). Instead of using thermal energy to emit electrons, a strong electric field is applied to create a potential barrier that allows electron tunneling, substituting a mechanical/electric mechanism for a thermal one and avoiding the harmful effects of high temperature

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Use of energy by moving object

If thermionic emission cathodes are heated to high temperatures to produce sufficient electron emission current, then electron emission capability is improved, but warm-up delays are introduced

Engineering Contradiction:

Improveelectron emission currentVSAvoidwarm-up delay

Core Design Contradiction:

Use of energy by moving objectVSLoss of time

Solution Approach 1:

The patent changes the emission mechanism from thermionic emission requiring high temperature to field emission operating at low temperature. By applying a strong electric field at the cathode surface, electrons are emitted through quantum tunneling without thermal heating, thus achieving sufficient electron emission current while dramatically extending cathode lifetime and eliminating warm-up delays

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent eliminates the need for preliminary heating action by using field emission. The cathode is prepared in advance to operate at low temperature, and electron emission is initiated immediately by applying the electric field, removing the warm-up delay entirely

Inventive Principle:

Principle #10Preliminary action

3Volume of moving object

If vacuum tube size is decreased to create smaller devices, then device miniaturization is achieved, but heat and reliability problems increase

Engineering Contradiction:

Improvedevice sizeVSAvoidheat and reliability problems

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent changes the emission mechanism from thermionic emission requiring high temperature to field emission operating at low temperature. This parameter change eliminates the heat generation problem that becomes critical in miniaturized devices, allowing small vacuum tubes to operate reliably without excessive heat while maintaining electron emission capability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the thermal field (heat-based thermionic emission) with an electric field (field emission). This substitution eliminates the harmful thermal effects that plague miniaturized vacuum tubes, enabling reliable operation in compact devices without the heat management problems that arise when thermionic cathodes are scaled down

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Use of energy by moving object

If thermionic emission cathodes are heated to high temperatures, then electron emission capability is improved, but auxiliary cooling equipment is required

Engineering Contradiction:

Improveelectron emission currentVSAvoidauxiliary cooling equipment

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent changes the emission mechanism from thermionic emission requiring high temperature to field emission operating at low temperature. By applying a strong electric field at the cathode surface, electrons are emitted through quantum tunneling without thermal heating, thus achieving sufficient electron emission current while dramatically extending cathode lifetime and eliminating warm-up delays

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent extracts and removes the high-temperature heating requirement from the electron emission process. By using field emission instead of thermionic emission, the system eliminates the need for heating mechanisms and associated cooling equipment, simplifying the overall device architecture while maintaining effective electron emission

Inventive Principle:

Principle #2Taking out (Extraction)

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 nanostructure-based field emission devices achieve higher power output and longer lifespan with reduced heat and reliability issues, enabling their use in various applications, including microwave systems, without the need for high-temperature heating.

Implementation Method 1

When a negative charge is applied to the nanotube field emitter, electrons can be emitted from the nanotube in the direction of elongation

Methodology Applied

Scientific EffectField emission: Electron Beam

Data Source

PatentUS9099272B2Field emission devices and methods for making the same

Publication Date: 2015.08.04 MICRON TECHNOLOGY INC

AI summary

The present disclosure includes field emission device embodiments. The present disclosure also includes method embodiments for forming field emitting devices. One device embodiment includes a housing defining an interior space including a lower portion and an upper portion, a cathode positioned in the lower portion of the housing, a elongate nanostructure coupled to the cathode, an anode positioned in the upper portion of the housing, and a control grid positioned between the elongate nanostructure and the anode to control electron flow between the anode and the elongate nanostructure.