A polycrystalline diamond micro-detector for X-ray absorption fine-structure measurements
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-02-16 |
| Journal | Journal of Synchrotron Radiation |
| Authors | LEI YAO, Yunpeng Liu, Bingjie Wang, Lixiong Qian, Xueqing Xing |
| Institutions | Chinese Academy of Sciences, University of Chinese Academy of Sciences |
| Citations | 6 |
| Analysis | Full AI Review Included |
Technical Documentation: MPCVD Diamond Micro-Detectors for XAFS
Section titled âTechnical Documentation: MPCVD Diamond Micro-Detectors for XAFSâExecutive Summary
Section titled âExecutive SummaryâThis documentation analyzes the successful fabrication and application of a Chemical Vapor Deposition (CVD) Polycrystalline Diamond (PCD) micro-detector for X-ray Absorption Fine-Structure (XAFS) measurements, demonstrating its viability as a replacement for traditional, bulky Ion Chambers (ICs).
- Material Validation: CVD PCD films (300 ”m thick) were successfully utilized to create a miniaturized, robust X-ray detector suitable for synchrotron applications.
- Performance Superiority: The PCD micro-detector achieved a signal-to-noise ratio (SNR) comparable to routine ICs while providing significantly higher response current (approximately 5x stronger at 8 keV).
- Enhanced Accuracy: XAFS fitting results for Cr and Fe foils showed that the PCD detector yielded near-neighbor bond lengths (R) closer to established crystallographic data compared to the routine IC.
- Miniaturization Advantage: The packaged detector dimensions (15 mm x 7.8 mm x 5.8 mm) are significantly smaller than routine ICs (110 mm x 110 mm x 352 mm), making it ideal for complex, combined Synchrotron Radiation (SR) experimental techniques.
- Energy Range: The detector proved effective for K-edge XAFS measurements across a wide energy spectrum, specifically 5.5 keV to 13.5 keV (Cr, Fe, Cu, and Se foils).
- 6CCVD Value Proposition: 6CCVD is uniquely positioned to supply the high-quality, custom-dimensioned PCD and Single Crystal Diamond (SCD) required for replicating and advancing this detector technology, including advanced metalization services.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Detector Material | Polycrystalline Diamond (PCD) | N/A | Chemical Vapor Deposition (CVD) |
| Diamond Film Thickness | ~300 | ”m | Self-supporting laminae |
| Diamond Cut Dimensions | 11 x 6 | mm | Active material size |
| Packaged Detector Dimensions | 15 x 7.8 x 5.8 | mm | Stainless steel shell |
| Electrode Material | Aluminum (Al) | N/A | Evaporated in vacuum |
| Electrode Thickness | < 100 | nm | Deposited on both sides |
| Operating Energy Range | 5.5 to 13.5 | keV | K-edge XAFS (Cr, Fe, Cu, Se) |
| Maximum Dark Current (PCD) | 38 (Stabilized at 30) | pA | Monitored for 1000 s |
| Response Current (PCD) | 3.2 | ”A | Incident X-rays at 8 keV |
| Response Current (IC) | 0.6 | ”A | Incident X-rays at 8 keV |
| Response Ratio (PCD/IC) | ~5 | N/A | PCD response is 5x stronger |
| Cr-Cr Distance (PCD) | 2.87 | Ă | Second subshell fit, closer to true value (2.88 Ă ) |
| Fe-Fe Distance (PCD) | 2.84 | Ă | Second subshell fit, more accurate than IC (2.90 Ă ) |
Key Methodologies
Section titled âKey MethodologiesâThe fabrication of the CVD diamond micro-detector involved precise material preparation and advanced thin-film deposition techniques:
- Material Sourcing: CVD diamond films (~300 ”m thick) were acquired.
- Precision Cutting: Films were cut into small pieces (11 mm x 6 mm) suitable for miniaturization.
- Surface Preparation: Decarburization and degreasing were performed using H2SO4 and NH4OH solutions.
- Electrode Patterning: Photoresist was applied to the four edges of the diamond piece to define the active area and prevent shorting.
- Metalization: Aluminum (Al) was evaporated in vacuum and deposited on both sides to form electrodes (8 mm x 5 mm, < 100 nm thick).
- Photoresist Removal: The photoresist was washed away, exposing the CVD diamond edges.
- Assembly: The diamond piece was mounted on a hollow circuit board (10 mm x 5 mm x 1.5 mm) and connected via gold wires.
- Encapsulation: The assembly was encapsulated with a 30 ”m thick polyimide insulation film and installed in a stainless steel shell (15 mm x 7.8 mm x 5.8 mm).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD provides the foundational MPCVD diamond materials and advanced processing services necessary to replicate, optimize, and scale the production of high-performance XAFS micro-detectors.
Applicable Materials
Section titled âApplicable MaterialsâThe research successfully utilized CVD Polycrystalline Diamond (PCD) to suppress diffraction spots and achieve high SNR. 6CCVD offers tailored materials for both high-flux and diffraction-sensitive applications:
- Optical Grade PCD: Ideal for replicating this study. 6CCVD offers PCD wafers up to 125 mm in diameter with custom thicknesses ranging from 0.1 ”m to 500 ”m, ensuring high uniformity and stability required for reliable detector performance.
- High Purity SCD: For applications where ultimate speed, lowest dark current (pA range), and highest radiation hardness are critical, 6CCVD supplies Single Crystal Diamond (SCD) plates up to 500 ”m thick. While SCD produces diffraction spots, its superior electronic properties may be necessary for certain high-speed or low-signal combined SR techniques.
- BDD Substrates: For specialized electrochemical or high-conductivity applications, Boron-Doped Diamond (BDD) substrates are available up to 10 mm thick.
Customization Potential
Section titled âCustomization PotentialâThe success of this micro-detector relies on precise dimensions and robust electrical contacts. 6CCVDâs in-house capabilities exceed the requirements outlined in the paper:
| Requirement from Paper | 6CCVD Capability | Optimization/Advantage |
|---|---|---|
| Diamond Size (11 mm x 6 mm) | Custom Dimensions & Laser Cutting | We provide precision laser cutting to any required geometry, ensuring tight tolerances for miniaturized devices. |
| Thickness (~300 ”m) | Thickness Control (0.1 ”m to 500 ”m) | We can fine-tune thickness to optimize X-ray transmission/absorption for specific energy ranges (e.g., thinner films for higher energy X-rays). |
| Electrode Material (Al) | Advanced Metalization Services | 6CCVD offers internal deposition of Au, Pt, Pd, Ti, W, and Cu. We can provide robust adhesion layers (e.g., Ti/Pt/Au stack) superior to simple Al, enhancing contact reliability and device longevity under high bias voltage (up to 2000 V used in the IC comparison). |
| Surface Finish | Polishing Services (Ra < 5 nm for PCD) | High-quality surface finish is critical for uniform electrode deposition and minimizing surface leakage currents, directly impacting dark current performance. |
Engineering Support
Section titled âEngineering SupportâThe successful application of diamond in XAFS detection confirms its role as a critical material in synchrotron science. 6CCVDâs in-house PhD team specializes in optimizing CVD diamond properties for radiation detection and high-energy physics. We offer comprehensive support for:
- Material Selection: Guiding researchers in choosing between PCD (for diffraction suppression) and SCD (for ultimate speed/low dark current) based on the specific combined SR technique (e.g., XAFS/XRD, XAFS/Raman).
- Device Design: Assisting with electrode design and metal stack selection to ensure optimal charge collection efficiency and long-term stability in high-radiation environments.
- Global Logistics: Offering reliable global shipping (DDU default, DDP available) to ensure materials reach synchrotron facilities worldwide promptly.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The microminiaturization of detectors used to record the intensity of X-ray beams is very favorable for combined X-ray experimental techniques. In this paper, chemical-vapor-deposited (CVD) polycrystalline diamond film was used to fabricate a micro-detector owing to its well controlled size, good thermostability, and appropriate conductivity. The preparation process and the main components of the CVD diamond micro-detector are described. The external dimensions of the packaged CVD diamond micro-detector are 15 mm Ă 7.8 mm Ă 5.8 mm. To demonstrate the performance of the detector, K -edge X-ray absorption fine-structure (XAFS) spectra of Cr, Fe, Cu, and Se foils were collected using the CVD diamond micro-detector and routine ion chamber. These XAFS measurements were performed at beamline 1W2B of Beijing Synchrotron Radiation Facility, covering an energy range from 5.5 to 13.5 keV. By comparison, it can be seen that the CVD diamond micro-detector shows a more excellent performance than the routine ion-chamber in recording these XAFS spectra. The successful application of the CVD diamond micro-detector in XAFS measurements shows its feasibility in recording X-ray intensity.