Process design for the manufacturing of soft X-ray gratings in single-crystal diamond by high-energy heavy-ion irradiation

At a Glance

Metadata	Details
Publication Date	2022-10-19
Journal	The European Physical Journal Plus
Authors	Y. Zamora Garcia, Michael Martin, M.D. Ynsa, V. Torres‐Costa, Miguel L. Crespillo
Institutions	ALBA Synchrotron (Spain), Universidad Politécnica de Madrid
Citations	12
Analysis	Full AI Review Included

Technical Documentation & Analysis: Single-Crystal Diamond Gratings via Swift Heavy-Ion Irradiation

This document analyzes the research paper “Process design for the manufacturing of soft X-ray gratings in single-crystal diamond by high-energy heavy-ion irradiation” to provide technical specifications and highlight how 6CCVD’s advanced MPCVD diamond capabilities can support and scale this innovative manufacturing process.

Executive Summary

This research validates a novel, non-mechanical method for manufacturing high-performance optical gratings in Single-Crystal Diamond (SCD) using highly focused Swift Heavy-Ion Irradiation (SHII).

Core Achievement: Successful creation of reproducible blazed grating topography (20 µm period, 15-25 nm swelling) on SCD substrates using 9 MeV ¹²C ions.
Material Advantage: The process leverages the superior thermal conductivity and radiation hardness of SCD, positioning it as the ideal substrate for next-generation synchrotron and Free Electron Laser (FEL) optics facing extreme heat loads (e.g., 10 mW/mm² at ALBA LOREA).
Methodology: Grating patterns are generated by controlled surface swelling, which is a direct consequence of buried structural damage induced by precise, pixel-by-pixel ion fluence mapping.
Scalability Challenge: The primary limitation identified for operational gratings is the current commercial availability of large-area, high-quality SCD substrates at a reasonable cost.
6CCVD Value Proposition: 6CCVD specializes in providing large-area, high-purity SCD and PCD wafers (up to 125mm) and custom thickness options (up to 500 µm), directly addressing the size and cost bottlenecks identified in the paper.
Future Optimization: The study suggests exploring heavier ion species (e.g., Si or Au) to reduce the required irradiation fluence and total manufacturing time, an area where 6CCVD can provide tailored substrate materials.

Technical Specifications

The following hard data points were extracted from the experimental setup and results for the simplified grating geometry:

Parameter	Value	Unit	Context
Substrate Material	Single-Crystal Diamond (SCD)	-	Optical Grade, Type IIa
Substrate Orientation	(100)	-	Used for implantation
Impurity Concentration (N/B)	< 1 ppm / 50 ppb	-	High purity requirement
Sample Dimensions (POC)	3 x 3 x 0.3	mm³	Proof-of-concept size
Ion Species / Charge State	¹²C⁺³	-	Swift Heavy-Ion Irradiation (SHII)
Ion Energy	9	MeV	Used for implantation
Focused Beam Size	5 x 2	µm²	Used for pixel-by-pixel scanning
Grating Period (Achieved)	~20	µm	50 lines/mm
Blaze Angle (Best Fit)	0.925	°	Determined by AFM data fitting
Surface Swelling (Range)	15 to 25	nm	Measured topography height
Minimum Fluence	10¹⁴	ions/cm²	Corresponds to ~1 nm swelling
Maximum Fluence	3 x 10¹⁵	ions/cm²	Used for grating pattern generation
LOREA Thermal Load (Max)	10	mW/mm²	Target operational environment
Diamond Young’s Modulus (E_d)	1220	GPa	Used in Finite Element Analysis (FEA)

Key Methodologies

The manufacturing process relies on precise control of ion fluence to induce localized damage and subsequent surface swelling, creating the desired topography.

Material Selection: Use of optical-grade, high-ppurity Single-Crystal Diamond (SCD, Type IIa) to ensure maximum radiation hardness and thermal stability under high-flux X-ray regimes.
Damage Mechanism Modeling: The target grating profile, $h(x)$, is quantified based on the total ion fluence $\Phi(x, y)$ and the linear nuclear energy density deposition $S_{n}(z)$ (calculated via SRIM simulation).
Fluence Profile Calculation: The required fluence profile $\Phi(x)$ is numerically solved from the swelling equation (Eq. 2) to match a target linear blaze geometry ($h(x) = A + Bx$).
Microbeam Irradiation: Implantation performed using a focused 9 MeV ¹²C⁺³ ion beam (5 x 2 µm²) in frontal geometry at the CMAM microbeam line.
Pixel-by-Pixel Scanning: A home-made software controls the beam position, scanning the sample in small steps along the dispersive direction, converting the calculated fluence map into discrete beam charge values ($Q$).
Topography Characterization: Surface morphology measured post-irradiation using Atomic Force Microscopy (AFM) under non-contact mode to confirm the achieved grating period and swelling height.
Elastic Modeling: Finite Element (FE) simulations (COMSOL Multiphysics) were used to model the material’s elastic response, confirming that pattern smoothing is primarily due to the material’s inherent properties and not just the beam size.

6CCVD Solutions & Capabilities

The research confirms that SCD is the necessary substrate for future high-heat-load X-ray optics, but highlights limitations in substrate size and manufacturing time. 6CCVD provides immediate, scalable solutions to overcome these bottlenecks.

Applicable Materials for Replication and Upscaling

The successful replication and upscaling of this SHII grating process requires high-quality, large-area diamond substrates.

6CCVD Material	Specification	Application Relevance
Optical Grade SCD	High purity (Type IIa equivalent), low N/B concentration. Thicknesses up to 500 µm.	Direct replacement for the material used in the study, ensuring maximum thermal conductivity (critical for high-heat-load optics).
Large-Area PCD	Plates/wafers up to 125 mm diameter. Thicknesses up to 500 µm.	While SCD is preferred for optical quality, large-area PCD offers a cost-effective, scalable alternative for initial prototyping or applications where minor grain boundaries are tolerable.
Custom Substrates	Substrates up to 10 mm thick.	Provides mechanical stability for large-area gratings or complex mounting requirements in synchrotron beamlines.

Customization Potential for Advanced Optics

6CCVD’s in-house capabilities directly address the engineering requirements for transitioning this proof-of-concept into operational devices.

Large-Area Substrates: The paper identifies the lack of large SCD crystals as a major limitation. 6CCVD offers custom SCD wafers and PCD plates up to 125 mm in diameter, enabling the manufacturing of operational, millimeter-length gratings.
Precision Polishing: To ensure optimal diffraction efficiency, the surface quality is paramount. 6CCVD guarantees ultra-low roughness polishing (Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD), exceeding standard commercial quality.
Custom Metalization: Operational gratings often require specific metal layers for mounting, heat sinking, or electrical contacts. 6CCVD offers internal metalization services including Au, Pt, Pd, Ti, W, and Cu, tailored to the specific beamline architecture.
Custom Dimensions and Shaping: We provide laser cutting and shaping services to deliver substrates with the exact dimensions and edge quality required for precise integration into monochromator translation stages.

Engineering Support for Ion Implantation Projects

The research suggests exploring heavier ion species (e.g., Si or Au) to reduce the required fluence and irradiation time—a critical step for upscaling.

Material Selection Expertise: 6CCVD’s in-house PhD team specializes in the material science of MPCVD diamond. We can assist researchers in selecting the optimal SCD or PCD grade to maximize damage efficiency and minimize unwanted elastic smoothing effects for Swift Heavy-Ion Irradiation (SHII) projects.
Thermal Management Consultation: We provide consultation on material thickness and doping (e.g., Boron-Doped Diamond, BDD, for enhanced electrical conductivity or specific thermal properties) to manage the extreme heat loads characteristic of advanced synchrotron and FEL facilities.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

Tech Support

Original Source

DOI: https://doi.org/10.1140/epjp/s13360-022-03358-3

References

1997 - Gratings, mirrors and slits: beamline design for soft X-ray synchrotron radiation sources