Zinc Oxide Coating Deposition via Segmented Precursor Streams
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Solution Overview
Problem
Existing methods for depositing zinc oxide coatings on substrates, particularly during float glass production, face challenges such as pre-reaction of dialkyl zinc compounds with other components in the precursor mixture, leading to blockages and incorporation of additives into the coating, which affects its properties.
Innovation Solution
A method using a precursor mixture comprising an alkyl zinc compound and a phosphorus source, specifically triethyl phosphite, which prevents pre-reaction and avoids incorporation of phosphorus into the zinc oxide coating, allowing for efficient deposition of high-quality zinc oxide coatings at high reaction rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dialkyl zinc compounds are used as precursors for zinc oxide deposition, then the deposition rate and coating quality are improved, but pre-reaction with other components in the precursor mixture occurs leading to blockages
Solution Approach 1:
The precursor mixture is segmented into separate streams: one containing the dialkyl zinc compound and another containing the oxygen source and phosphorus source. These streams are mixed only at the substrate surface, preventing pre-reaction in the delivery apparatus while enabling high-rate deposition at the target.
Solution Approach 2:
An inert carrier gas acts as an intermediary medium to transport the dialkyl zinc compound and other precursors separately to the substrate surface without allowing them to react prematurely. The carrier gas isolates the reactive components until they reach the deposition zone.
2Reliability
If additives are incorporated in the CVD precursor mixture to slow pre-reaction, then pre-reaction is reduced, but additives become incorporated into the zinc oxide coating affecting its properties
Solution Approach 1:
The harmful effect of pre-reaction is eliminated by removing the opportunity for reaction between dialkyl zinc and oxygen sources until the precursors reach the substrate surface. The separate stream delivery system extracts the pre-reaction problem from the deposition process, allowing pure zinc oxide coating formation without additive contamination.
3Reliability
If separate precursor streams are used to prevent pre-reaction, then blockages are avoided, but the device complexity increases
Solution Approach 1:
Multiple precursor streams are merged at the substrate surface in a controlled manner. The mixing occurs naturally at the deposition zone where all precursors converge on the hot substrate, combining the benefits of separate transport (no pre-reaction) with simultaneous deposition (high rate) without requiring complex mixing apparatus.
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 method enables the deposition of thick, high-quality zinc oxide coatings without pre-reaction issues or phosphorus incorporation, suitable for on-line coating during float glass production, and can be used in photovoltaic cells and other applications.
Implementation Method 1
Chemical vapour deposition (CVD) is a type of pyrolysis whereby the precursors are delivered to the substrate surface in vapour or gaseous form
Implementation Method 2
One coating method is pyrolysis, wherein fluid precursors (often in an inert carrier) are delivered to the substrate surface and react thereby depositing a coating
Data Source
AI summary
The present invention relates to a method of depositing a coating comprising zinc oxide on a substrate; to a chemical vapour deposition precursor mixture for use in same and to a coated glass article and a photovoltaic cell prepared with a zinc oxide coating prepared using the method which comprises: providing a substrate, providing a precursor mixture comprising an alkyl zinc compound and a phosphorus source, the phosphorus source comprising a compound of formula OnP(OR)3, wherein n is 0 or 1 and each R is hydrocarbyl, and delivering the precursor mixture to a surface of the substrate.