Nanostructure Field Emission Cathode with Coaxial Gate
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional field emission devices, such as Spindt cathodes and carbon nanotube (CNT) emitters, face limitations in stability, vacuum requirements, and control over emission current density and uniformity, which hinder their practical application in high-resolution electron optical devices.
Innovation Solution
The development of nanostructure field emission devices with a resistive layer, connection pad, and coaxial gate electrodes, where the nanostructure elements like CNTs, ZnO, or TiO2 are grown on a resistive layer with a connection pad, and a coaxial gate structure is formed around them, enhancing stability and control over emission current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single needle shape emitter with sharp tip is used, then high resolution electron emission is achieved, but total emission current is limited due to tiny emission area
Solution Approach 1:
The cathode is divided into multiple individual needle-shaped emitters arranged in an array, each with a sharp tip for high resolution emission. By segmenting the emission surface into many independent emitters, the patent simultaneously maintains high resolution at each tip while achieving high total current through the cumulative effect of all emitters in the array.
2Quantity of substance
If a metal emitter array is used to increase total emission current, then emission current is improved, but lifetime is reduced to just a few seconds in medium level vacuum
Solution Approach 1:
The patent changes the material parameter from metal to carbon-based nanotubes, which have fundamentally different properties including higher chemical stability and resistance to vacuum degradation. This material substitution allows the emitters to maintain high current emission capability while extending operational lifetime from seconds to much longer durations in medium level vacuum environments.
3Reliability
If carbon nanotube emitters are grown on resistive materials, then stability in medium vacuum is improved, but proper function is not achieved
Solution Approach 1:
The patent employs a composite structure where carbon nanotube emitters are grown on a substrate with specific electrical properties. The composite design integrates the stability advantages of carbon nanotubes in medium vacuum with the electrical conductivity needed for proper function, creating a hybrid system that achieves both reliability and operational effectiveness.
4Quantity of substance
If conventional field emission devices are used, then emission current is achieved, but control over emission current density and uniformity is poor
Solution Approach 1:
Each needle-shaped emitter in the array is designed with identical geometric parameters and sharp tip characteristics, ensuring uniform local emission properties across all emitters. This local quality control, combined with the array configuration, enables precise control over overall emission current density and uniformity, as each emitter contributes equally to the total emission.
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
This configuration improves the robustness and stability of field emission devices, allowing for higher emission current density, reduced gate voltage requirements, and longer operational stability without the need for ultra-high vacuum conditions, making them suitable for various electronic applications.
Implementation Method 1
Field emission cathodes have been successfully used in high resolution electron optical devices
Data Source
AI summary
Various embodiments are described herein for nanostructure field emission cathode structures and methods of making these structures. These structures generally comprise an electrode field emitter comprising a resistive layer having a first surface, a connection pad having a first surface disposed adjacent to the first surface of the resistive layer, and a nanostructure element for emitting electrons in use, the nanostructure element being disposed adjacent to a second surface of the connection pad that is opposite the first surface of the connection pad. Some embodiments also include a coaxial gate electrode that is disposed about the nanostructure element.