Biaxially Textured Thin Films for Low-Misorientation Superconductor Tapes
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Solution Overview
Problem
Existing thin films used in flexible electronics and superconductor tapes have in-plane textures greater than 6°, leading to high misorientations and twin orientations that degrade electronic, opto-electronic, and electrical properties.
Innovation Solution
Fabrication of biaxially-textured films with in-plane textures less than 2° using Ion Beam-Assisted Deposition (IBAD) templates, followed by homo-epitaxial layers of MgO or TiN, and epitaxial films of silver, germanium, silicon, or GaAs, with optional annealing to remove twin orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Ion Beam-Assisted Deposition (IBAD) templates are used to fabricate thin films, then the films can be produced on inexpensive substrates, but the in-plane texture is limited to about 6° which is inferior to single crystal wafers
Solution Approach 1:
An intermediate biaxially-textured buffer layer is introduced between the IBAD template and the epitaxial film. This buffer layer serves as a mediator that improves the in-plane texture from 6° to less than 2° while maintaining compatibility with inexpensive substrates, thus resolving the contradiction between manufacturing precision and ease of manufacture
Solution Approach 2:
The film structure is segmented into multiple layers: IBAD template layer, biaxially-textured buffer layer, and epitaxial film layer. This segmentation allows each layer to perform its specific function - the IBAD layer provides substrate compatibility, the buffer layer improves texture, and the epitaxial layer delivers high-performance material properties
2Ease of manufacture
If amorphous silicon is used in flexible electronics, then the devices can be made flexible and inexpensive, but the carrier mobility is only 1-10 cm2/Vs which is far below crystalline silicon
Solution Approach 1:
The crystal structure parameter of silicon is changed from amorphous to epitaxial crystalline by using the biaxially-textured buffer layer as a template. This parameter change dramatically improves carrier mobility from 1-10 cm2/Vs to levels comparable with bulk crystalline silicon, while maintaining flexibility and low cost through the thin-film epitaxial structure
3Ease of manufacture
If buffer layers with in-plane texture of about 6° are used on IBAD templates, then the films can be grown on inexpensive substrates, but the misorientations between grain boundaries are high which degrades electronic properties
Solution Approach 1:
The biaxially-textured buffer layer acts as an intermediary that reduces misorientations between grain boundaries from 6° to less than 2°. This intermediate layer mediates between the inexpensive IBAD substrate and the high-performance epitaxial film, eliminating the harmful effect of high misorientations
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 resulting films exhibit superior electronic, opto-electronic, and electrical properties, with improved carrier mobility, conversion efficiency, and critical current density, surpassing previous performance levels.
Implementation Method 1
Previously, templates made using Ion Beam-Assisted Deposition (IBAD) have yielded superior quality Ge, Si and GaAs films
Implementation Method 2
forming a homo-epitaxial film of MgO or TiN above the IBAD template layer; and forming a film of silver epitaxially above the MgO or TiN film
Implementation Method 3
with optional annealing to remove twin orientations
Data Source
AI summary
A superconductor tape and method for fabricating same are disclosed. Embodiments are directed to a superconductor tape including a substrate and a buffer stack. In one embodiment, the buffer stack includes: an Ion Beam-Assisted Deposition (IBAD) template layer above the substrate; a homo-epitaxial film of MgO or TiN above the IBAD template layer; an epitaxial film of silver above the homo-epitaxial film; and a homo-epitaxial film of LaMnO3 (LMO) above the silver epitaxial film. The superconductor tape also includes a superconductor film above the buffer stack. These and other embodiments achieve a LMO film with substantially improved texture, resulting in a superconductor structure having high critical current and significantly reduced power consumption and cost.