CVD Mono-crystalline Diamond Growth via Nitrogen Concentration Control
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Solution Overview
Problem
Current chemical vapor deposition (CVD) methods for growing mono-crystalline diamonds often result in defects such as micro cracks, micro inclusions, and graphitic inclusions due to high nitrogen concentrations, which deteriorate the electrical, optical, and mechanical properties of the diamonds.
Innovation Solution
A CVD process using small amounts of nitrogen and optionally diborane in the gas mixture, within specific concentration ranges (0.0001 to 0.02 vol% for nitrogen and 0.00002 to 0.002 vol% for diborane), to promote a step-growth mechanism that avoids defects and graphitic inclusions, resulting in high-quality, gem-quality diamonds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high nitrogen concentration is used in CVD gas mixture, then diamond growth rate is enhanced, but nitrogen-based defects and graphitic inclusions are formed
Solution Approach 1:
The patent applies parameter changes by precisely controlling the nitrogen concentration in the CVD gas mixture to a specific range (0.01-5% nitrogen to carbon-compound gas ratio). This optimized parameter range enables the diamond crystal to grow at a high rate while avoiding the formation of nitrogen-based defects and graphitic inclusions, thus resolving the contradiction between growth rate and crystal quality
2Productivity
If nitrogen is added to CVD gases, then growth rates increase, but lattice defects are created
Solution Approach 1:
The patent changes the nitrogen concentration parameter to a specific range (0.01-5% nitrogen to carbon-compound gas ratio) that optimizes both growth rate and crystal perfection. Within this range, nitrogen promotes adequate growth while preventing excessive nitrogen incorporation that would create lattice defects, thereby resolving the contradiction between productivity and reliability
3Productivity
If nitrogen is added to CVD gases, then growth rates increase, but diamond purity is reduced
Solution Approach 1:
The patent applies parameter changes by controlling nitrogen concentration within the specific range of 0.01-5% nitrogen to carbon-compound gas ratio. This optimized parameter enables high growth rates while maintaining diamond purity by preventing excessive nitrogen incorporation and graphitic inclusion formation, thus resolving the contradiction between productivity and substance quality
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 process produces mono-crystalline diamonds with enhanced optical, electrical, and mechanical properties by minimizing nitrogen-based defects and inclusions, approaching the quality of natural diamonds.
Implementation Method 1
growing diamonds by chemical vapour deposition (CVD) processes
Implementation Method 2
controlling the quantity of nitrogen-containing gas relative to other gases in the reaction gases such that diamond is caused to grow by step-growth
Data Source
AI summary
A method of forming mono-crystalline diamond by chemical vapor deposition, the method comprising the steps of: (a) providing at least one diamond seed; (b) exposing the seed to conditions for growing diamond by chemical vapor deposition, including supplying reaction gases that include a carbon-containing gas and hydrogen for growing diamond and include a nitrogen-containing gas; and (c) controlling the quantity of nitrogen-containing gas relative to other gases in the reaction gases such that diamond is caused to grow by step-growth with defect free steps without inclusions. The nitrogen is present in the range of 0.0001 to 0.02 vol %. Diborane can also be present in a range of from 0.00002 to 0.002 vol %. The carbon-containing gas can be methane.