Nanoscale Diamond Marking via Two-Photon Lithography
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Solution Overview
Problem
Existing methods for marking diamonds and gemstones, such as laser marking and FIB marking, face challenges in creating fine patterns without damaging the surface and leaving visible marks, which are not suitable for unique identification and security purposes.
Innovation Solution
A method combining two-photon absorption lithography and plasma etching to create non-optically detectable marks on the surface of solid state materials like diamonds, using recesses and apertures that are smaller than 200 nm, making them invisible in the visible light spectrum but detectable in UV light, allowing for secure and non-damaging identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser marking is used to mark diamond surface, then marking can be formed by ablation, but the large heat affected zone causes damage to the diamond and leaves visible darkened marks
Solution Approach 1:
The patent replaces thermal ablation (laser heating) with mechanical sputtering (ion beam bombardment). The FIB system uses focused gallium ions to physically remove material through momentum transfer, avoiding the thermal diffusion that causes HAZ and graphite formation in laser marking. This mechanical substitution resolves the contradiction by achieving precise material removal without thermal damage.
Solution Approach 2:
The patent changes the marking mechanism from thermal process to physical sputtering process. By using ion beam with controlled energy (typically 5-30 keV) and low current density, material is removed through physical ejection rather than thermal vaporization. This parameter change eliminates the heat affected zone while maintaining marking precision.
2Manufacturing precision
If laser marking is used to create fine patterns, then marking can be formed, but the laser spot size is too large to generate fine patterns
Solution Approach 1:
The patent replaces laser beam focusing with ion beam focusing. The FIB system uses electromagnetic lenses to focus gallium ions to a spot size of 10-100 nm, which is one to two orders of magnitude smaller than the best laser spot size. This mechanical substitution enables creation of fine patterns that are impossible with laser marking.
3Manufacturing precision
If FIB marking is used to create fine patterns, then high-resolution marks can be inscribed, but the process is complex and time-consuming
Solution Approach 1:
The patent uses a mask layer (photoresist or deposited film) as a template to copy the desired pattern onto the diamond surface. The mask is prepared separately with the identification pattern, then transferred to the diamond through aligned deposition or lithography. This copying approach simplifies the FIB process by providing a pre-defined pattern that guides the ion beam, reducing complexity compared to direct free-form FIB writing.
4Reliability
If laser marking is used to mark diamond, then identification mark can be formed, but the mark is visible to naked eye which compromises security
Solution Approach 1:
The patent creates marks with local quality differences at the nanoscale that are invisible to the naked eye but detectable with specialized equipment. The FIB process creates subtle surface modifications (nanoscale pits, ridges, or compositional changes) that require UV illumination or electron microscopy to visualize. This local quality approach maintains identification reliability while eliminating visible marks that could compromise security.
Solution Approach 2:
The patent utilizes UV-responsive marking where the identification mark becomes visible only under UV illumination. The FIB process creates structures that scatter or absorb UV light differently than the surrounding diamond, creating a visible contrast under UV but remaining invisible under normal visible light. This color/illumination change approach resolves the contradiction between reliable identification and security.
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 secure, non-damaging, and non-visible marking of diamonds and gemstones, suitable for anti-counterfeiting and identification purposes, without altering their optical properties or introducing contaminants, providing a unique and invisible mark that can be detected using specialized techniques.
Implementation Method 1
forming a plurality of recesses within a predetermined region of a photoresist applied to an outer surface of an article formed from a solid state material, wherein said plurality of recesses is formed by two-photon absorption lithography
Implementation Method 2
applying an etching process such that at least a portion of the outer surface of said article is exposed and etched so as to form a plurality of etched portions extending into said article from the outer surface of the article and corresponding to said plurality of recesses
Data Source
AI summary
A method of forming a non-optically detectable identifiable mark at an outer surface of an article formed from a solid state material, said method including the steps of forming a plurality of recesses within a predetermined region of a photoresist 5 applied to an outer surface of an article formed from a solid state material, wherein said plurality of recesses is formed by two-photon absorption lithography and wherein said one or more recesses extend at least partially through the photoresist and from an outer surface of the photoresist and towards said outer surface of the article 10 formed from a solid state material; and applying an etching process such that at least a portion of the outer surface of said article is exposed and etched so as to form a plurality of etched portions extending into said article from the outer surface of the article and corresponding to said plurality of recesses; wherein said predetermined region of said photoresist defines an identifiable mark to be applied to the outer 15 surface of said article; wherein said plurality of etched portions forms the nonoptically identifiable mark on the outer surface of said article; and wherein the maximum width of the etched portions of is less than 200 nm such that the identifiable mark is non-optically detectable in the visible light spectrum.