Oxide Superconductor Thin Film with Smooth Buffer Layer
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Solution Overview
Problem
Oxide superconducting thin films with intermediate layers of 20 nm or less tend to form island-like structures, leading to holes that cause a decrease in critical current density (Jc) characteristics due to reactions between the superconducting layer and the substrate.
Innovation Solution
An oxide superconducting thin film with an intermediate layer of 10-20 nm thickness and surface roughness of 0.5 nm or less, composed of CeO2 or MgO with specific valence values, is formed on a substrate with dislocation at the interface, preventing island formation and enhancing Jc characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the intermediate layer is reduced to improve Jc characteristics, then the critical current density improves, but the intermediate layer forms island-like structures with holes that cause reactions between the superconducting layer and substrate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the intermediate layer within the range of 5-20 nm and maintaining surface roughness Ra of 0.5 nm or less. This optimization of dimensional parameters prevents island formation while preserving high Jc characteristics, resolving the contradiction between thinning the layer for better performance and maintaining structural integrity.
Solution Approach 2:
The patent applies local quality by creating a gradient in layer thickness and composition. The intermediate layer has varying thickness across different regions, being thinner in areas where high Jc is needed while maintaining sufficient coverage to prevent substrate reactions. This local variation in quality allows simultaneous achievement of high critical current density and structural stability.
2Manufacturing precision
If the intermediate layer is made thinner to reduce lattice mismatch, then the Jc characteristics improve, but the layer becomes unstable and forms holes
Solution Approach 1:
The patent applies composite materials by using a multi-layer structure consisting of the substrate, intermediate layer (CeO2 or MgO), and superconducting layer (YBCO). The intermediate layer acts as a buffer with specific material properties that reduce lattice mismatch between the substrate and superconducting layer while maintaining sufficient thickness and smoothness to prevent hole formation, thus achieving both precision and stability.
Solution Approach 2:
The patent applies the intermediary principle by introducing CeO2 or MgO as an intermediate buffer layer between the substrate and the YBCO superconducting layer. This intermediary layer mediates the lattice mismatch issue, allowing the thin layer configuration for high Jc while preventing direct contact and reactions between the substrate and superconducting layer, thereby maintaining structural stability.
3Reliability
If the surface roughness is reduced to prevent island formation, then the Jc characteristics improve, but the manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by establishing specific quantitative thresholds for surface roughness (Ra ≤ 0.5 nm) and thickness (5-20 nm). These well-defined parameter ranges provide clear manufacturing targets that balance the need for smooth surfaces to prevent island formation with the practical constraints of manufacturing complexity, enabling reproducible high-quality films.
Solution Approach 2:
The patent applies preliminary action by performing surface preparation and intermediate layer formation with precise roughness control before depositing the superconducting layer. This preliminary smoothing action prevents subsequent island formation during superconducting layer deposition, ensuring high Jc characteristics while managing manufacturing complexity through staged process control.
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 solution results in favorable Jc characteristics and a superconducting fault current limiter with improved performance by preventing substrate reactions and maintaining a smooth interface, thus maintaining high electrical conductivity.
Implementation Method 1
an intermediate layer and a superconducting layer which are provided in this order on the substrate... preventing substrate reactions and maintaining a smooth interface
Implementation Method 2
RE-based superconductors (RE: rare earth element), which exhibit a superconducting phenomenon at liquid nitrogen temperature (77 K) or higher
Data Source
AI summary
An oxide superconducting thin film includes a substrate, and an intermediate layer and a superconducting layer provided in this order on the substrate. The intermediate layer has an average thickness of from 10 nm to 20 nm and a surface roughness Ra of 0.5 nm or less. The superconducting layer is formed on a surface of the intermediate layer and includes an oxide superconductor as a main component. A superconducting fault current limiter including the oxide superconducting thin film is also provided.