Titanium Oxide Film Stabilization for Void-Free Coatings
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Solution Overview
Problem
Existing sol-gel materials struggle to form transparent, high-refractive index coatings on substrates with nano-sized or micro-sized recessed features without voiding or increased light absorption, especially when exposed to thermal or photo-induced interactions.
Innovation Solution
Incorporation of titanium oxide stabilizers with in-situ produced carboxylate groups in sol-gel materials to prevent interactions with the environment and residual organics, allowing for superconformal filling of surface-relief structures at low temperatures (≤300°C) with low light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sol-gel materials are thermally annealed to densify the oxide network and form transparent coatings, then the refractive index increases and transparency improves, but voids form in recessed features and light absorption increases
Solution Approach 1:
The patent applies preliminary action by performing low-temperature annealing (≤300°C) before high-temperature processing to pre-densify the sol-gel material and fill recessed features. This preliminary densification prevents void formation during subsequent high-temperature annealing while maintaining transparency, as the material is already compacted and less prone to shrinkage-induced voiding.
Solution Approach 2:
The patent employs parameter changes by optimizing the annealing temperature profile, specifically using low annealing temperatures (≤300°C) to control the densification process. This temperature parameter change allows sufficient densification to fill recessed features without excessive thermal contraction that would create voids, thereby resolving the contradiction between transparency and void-free filling.
2Manufacturing precision
If sol-gel materials are fully densified through high-temperature annealing to remove organics, then transparency improves, but the material shrinks and creates voids in surface-relief structures
Solution Approach 1:
The patent applies preliminary action by performing low-temperature annealing (≤300°C) before high-temperature processing to pre-densify the sol-gel material and fill recessed features. This preliminary densification prevents void formation during subsequent high-temperature annealing while maintaining transparency, as the material is already compacted and less prone to shrinkage-induced voiding.
Solution Approach 2:
The patent employs parameter changes by optimizing the annealing temperature profile, specifically using low annealing temperatures (≤300°C) to control the densification process. This temperature parameter change allows sufficient densification to fill recessed features without excessive thermal contraction that would create voids, thereby resolving the contradiction between transparency and void-free filling.
3Manufacturing precision
If annealing temperature is increased to remove residual organics and improve transparency, then light absorption decreases, but the processing temperature exceeds 300°C causing material instability
Solution Approach 1:
The patent employs parameter changes by optimizing the annealing temperature to ≤300°C, balancing organic removal with material stability. This temperature parameter change allows sufficient organic decomposition to achieve low light absorption while preventing excessive thermal effects that would cause material instability or void formation.
Solution Approach 2:
The patent applies continuity of useful action by using multiple annealing steps or extended low-temperature annealing to progressively remove organics without exceeding 300°C. This continuous low-temperature processing achieves thorough organic removal and low light absorption while maintaining material stability throughout the process.
4Reliability
If sol-gel material viscosity is increased to prevent voiding during annealing, then the material fills recessed features better, but the material cannot superconformally fill high-aspect-ratio structures
Solution Approach 1:
The patent applies preliminary action by performing low-temperature annealing (≤300°C) before high-temperature processing to pre-densify the sol-gel material and fill recessed features. This preliminary densification prevents void formation during subsequent high-temperature annealing while maintaining transparency, as the material is already compacted and less prone to shrinkage-induced voiding.
Solution Approach 2:
The patent employs parameter changes by optimizing the annealing temperature profile, specifically using low annealing temperatures (≤300°C) to control the densification process. This temperature parameter change allows sufficient densification to fill recessed features without excessive thermal contraction that would create voids, thereby resolving the contradiction between transparency and void-free filling.
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
Achieves transparent, void-free coatings with refractive indices of 1.6-1.9 and absorption rates less than 0.1% per 100 nm, maintaining stability over time and temperature.
Implementation Method 1
Upon coating and thermal annealing of the solution, precursor ligands and solvents may be thermally removed to fully condense the extended network into an oxide film
Implementation Method 2
precursor ligands and solvents may be thermally removed
Implementation Method 3
titanium oxide stabilizer including R3OC(O)OR4, R5C(O)OR6, or a combination... to prevent interactions between the metal oxides and the environment
Implementation Method 4
superconformally fills surface-relief structures
Data Source
AI summary
A sol-gel material for overcoating a surface-relief structure includes a titanium(IV) precursor, and a titanium oxide stabilizer including R3OC(O)OR4, R5C(O)OR6, or a combination. R3 and R4 include alkyl or alkene groups optionally containing carboxylate, alcohol, or ester functionalities, such as propylene carbonate (PC). R5 and R6 include alkyl or alkene groups optionally containing carboxylate, alcohol, or ester functionalities, for example, a lactone such as gamma butyrolactone (GBL). In some embodiments, the sol-gel material includes a source of sulfate or phosphate anions, an acid, a base, a peroxide, a surfactant, a cross-linker, a flexibilizer, a toughener additive, a solvent, or a combination thereof. In some embodiments, the sol-gel material is annealed at a temperature between 50-150° C., and then annealed at a temperature between 200-300° C. In some embodiments, the sol-gel material is cured using ultraviolet light before annealing at a temperature between 200-300° C.