MIS Field Emission Gate Materials for Stable X-Ray Generation
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Solution Overview
Problem
Existing field emission devices suffer from inadequate field emission performance, reliability, and stability, particularly in X-ray generating apparatuses using Metal Insulator Semiconductor (MIS) structures, necessitating improvements in semiconductor, insulating, and gate electrode layer conditions for enhanced X-ray generation efficiency and reliability.
Innovation Solution
A field emission device with a semiconductor substrate, bottom electrode, insulating layer, and gate electrode, where the gate electrode is composed of materials meeting specific conditions for work function, Gibbs free energy of redox reaction, sublimation energy, and electron mean free path, along with optimized semiconductor and insulating layer thicknesses, to enhance performance and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gate electrode materials are used in MIS structure field emission devices, then device simplicity is maintained, but field emission performance, reliability, and stability are insufficient
Solution Approach 1:
The patent applies parameter changes by establishing specific quantitative conditions for gate electrode materials including work function (5.0-6.0 eV), Gibbs free energy (>0 for redox reaction with insulating layer), sublimation energy (>300 kJ/mol), and electron mean free path (>0.9 nm). These parameter specifications transform the gate electrode selection from a simple material choice into a precisely controlled design process that ensures superior field emission performance, reliability, and stability.
2Productivity
If gate electrode material is optimized for work function, then electron emission efficiency improves, but material selection constraints increase
Solution Approach 1:
The patent employs composite materials principle by specifying that the gate electrode should be composed of metal compounds rather than pure metals. This approach allows combining multiple elements to achieve the required work function range (5.0-6.0 eV) while simultaneously satisfying other conditions such as Gibbs free energy, sublimation energy, and electron mean free path. The composite structure provides both high electron emission efficiency and sufficient material selection flexibility.
3Reliability
If thinner insulating layer is used to improve electron tunneling, then field emission performance increases, but thermal stability and reliability decrease
Solution Approach 1:
The patent resolves this contradiction by establishing an optimized insulating layer thickness range of 5-30 nm. This parameter specification balances electron tunneling efficiency with thermal stability: the thickness is sufficiently thin to allow effective electron tunneling for high field emission performance, yet sufficiently thick to maintain thermal stability and prevent breakdown. The patent further specifies that the insulating layer should be composed of oxide materials with appropriate band gap energies to enhance both tunneling and stability.
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 proposed configuration improves field emission performance, reliability, and stability by minimizing electron scattering and diffusion, ensuring high tunneling current and thermal stability, thereby enhancing the efficiency and reliability of X-ray generation.
Implementation Method 1
a field emission device which generates X-rays by emitting an electron beam
Implementation Method 2
ensuring high tunneling current
Implementation Method 3
an anode generating X-rays by collision with electrons emitted from the electron beam emission region
Data Source
AI summary
The present disclosure relates to a field emission device that generates X-rays by emitting an electron beam, and an X-ray generating apparatus using the same, including a semiconductor substrate; a bottom electrode disposed below the semiconductor substrate; an insulating layer disposed above the semiconductor substrate; a gate electrode disposed on the insulating layer; and, a top electrode disposed on the gate electrode; wherein the gate electrode is composed of a material satisfying at least one of a first condition for work function, a second condition for Gibbs free energy of a redox reaction with the insulating layer, a third condition for sublimation energy, and a fourth condition for electron mean free path.