Синтез CVD-алмаза детекторного качества для радиационно-стойких детекторов ионизирующего излучения
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2022-01-01 |
| Journal | Журнал технической физики |
| Authors | А.В. Красильников, Н.Б. Родионов, А.П. Большаков, В.Г. Ральченко, С.К. Вартапетов |
| Citations | 3 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Detector-Grade MPCVD Diamond Synthesis
Section titled “Technical Documentation & Analysis: Detector-Grade MPCVD Diamond Synthesis”This document analyzes the research paper detailing the synthesis of high-quality, homoepitaxial Single Crystal Diamond (SCD) films via Microwave Plasma Chemical Vapor Deposition (MPCVD) for use in radiation-resistant ionizing radiation detectors. The findings confirm the viability of MPCVD SCD as a superior material for high-energy physics and fusion research (e.g., ITER).
Executive Summary
Section titled “Executive Summary”The following points summarize the core achievements and material requirements outlined in the research, directly aligning with 6CCVD’s advanced SCD manufacturing capabilities:
- High Performance: Successful synthesis of detector-grade SCD films (70-80 µm thick) achieving near-unity Charge Collection Efficiency (CCE).
- Exceptional CCE: Measured CCE reached 94% for 5.5 MeV alpha particles and 91% for 14.7 MeV neutrons, demonstrating high material purity and crystalline perfection.
- Low Impurity Profile: Nitrogen impurity concentration (Ns0) in the epitaxial films was experimentally confirmed to be below 50 ppb, a critical requirement for minimizing charge trapping.
- Crystalline Quality: High structural perfection was verified by narrow Raman peak Full Width at Half Maximum (FWHM) values, as low as 2.2 cm-1, which correlated directly with improved CCE.
- Detector Architecture: The devices utilized a p-i structure, employing highly Boron-Doped Diamond (BDD) substrates as the conductive p-type back contact for homoepitaxial growth.
- Application Focus: The resulting detectors exhibit high stability and are suitable for extreme environments, specifically targeting applications in high-energy physics and thermonuclear plasma diagnostics.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the synthesis and performance measurements:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Material Type | Homoepitaxial SCD | N/A | Grown on B-doped HPHT substrates |
| Active Layer Thickness (d) | 70 - 80 | µm | CVD film thickness (B21, B22) |
| Substrate Boron Concentration | ~100 | ppm | p-type conductive layer |
| Nitrogen Impurity (Ns0) | < 50 | ppb | In epitaxial film, critical for detector grade |
| Charge Collection Efficiency (CCE) | 94 | % | Maximum measured CCE (5.5 MeV Alpha) |
| CCE (Neutrons) | 91 | % | Measured CCE (14.7 MeV Neutrons) |
| Estimated Energy Resolution (ΔE/E) | 1.7 | % | For B21 film (after correcting for air losses) |
| Raman FWHM (B21) | 2.2 | cm-1 | Correlates with highest crystalline quality |
| Substrate Temperature (Ts) | 940 - 1050 | °C | During MPCVD growth |
| Growth Rate (GR) | 3.0 - 4.0 | µm/h | Typical rate for detector-grade material |
| Contact Metalization | Platinum (Pt) | 35 nm | Sputtered contacts |
Key Methodologies
Section titled “Key Methodologies”The synthesis of detector-grade SCD films relied on precise control of the MPCVD environment and rigorous material preparation:
- Reactor System: Synthesis was performed in a specially modified ARDIS-300 MPCVD reactor (2.45 GHz, up to 6 kW power), optimized to minimize atmospheric leakage and background nitrogen contamination.
- Substrate Selection: Highly Boron-Doped (BDD) HPHT diamond substrates (p-type, ~100 ppm B) were used, typically 4.5 x 4.5 x 0.5 mm in size and oriented (100).
- Surface Preparation: Substrates underwent high-temperature annealing (590°C in air) to remove non-diamond carbon, followed by boiling in concentrated sulfuric acid/potassium dichromate solution, and ultrasonic cleaning in isopropanol.
- Gas Composition: High-purity H2 and CH4 were used. Typical methane concentration was 4% in the gas phase for detector-grade films (B21-B23).
- Process Parameters: Synthesis pressure was maintained at 170 Torr, with substrate temperatures ranging from 940°C to 965°C, achieving growth rates of 3.0-4.0 µm/h.
- Post-Growth Processing: One sample (B23) was mechanically polished to reduce the final active layer thickness from 80 µm to 60 µm.
- Detector Fabrication: Platinum (Pt) contacts (35 nm thick) were deposited via magnetron sputtering at 250°C onto both the homoepitaxial film (front) and the conductive BDD substrate (back).
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”6CCVD is uniquely positioned to supply the advanced diamond materials and custom fabrication services required to replicate and extend this high-performance radiation detector research.
Applicable Materials for Replication and Extension
Section titled “Applicable Materials for Replication and Extension”To achieve the high CCE and low impurity profile demonstrated in this research, 6CCVD recommends the following specialized materials:
- Active Layer Material: Optical/Detector Grade Single Crystal Diamond (SCD). Our MPCVD process ensures ultra-low nitrogen incorporation (< 5 ppb achievable) and high crystalline perfection (Raman FWHM < 2.0 cm-1), surpassing the quality metrics cited in the paper (2.2 cm-1).
- Substrate Material: Heavy Boron-Doped Diamond (BDD) Substrates. We provide highly conductive BDD substrates (p-type) up to 10 mm thick, capable of matching the required ~100 ppm Boron concentration for robust back contacts in p-i-n detector architectures.
Customization Potential & Fabrication Services
Section titled “Customization Potential & Fabrication Services”The research utilized specific dimensions, thicknesses, and metal contacts. 6CCVD offers full customization to meet these exact engineering requirements:
| Research Requirement | 6CCVD Capability | Advantage for Researchers |
|---|---|---|
| Thickness | SCD films from 0.1 µm up to 500 µm. | Precise control over active layer thickness for optimizing charge collection distance (CCD) and bias voltage requirements. |
| Dimensions | Custom plates/wafers up to 125 mm (PCD). | While SCD is typically smaller, we offer custom SCD sizes and can scale PCD detectors significantly beyond the 4.5 x 4.5 mm size used. |
| Metalization | Internal capability for Au, Pt, Pd, Ti, W, Cu. | We can replicate the required 35 nm Platinum (Pt) contacts or provide optimized multi-layer stacks (e.g., Ti/Pt/Au) for enhanced adhesion and stability. |
| Surface Quality | SCD polishing to Ra < 1 nm. | Superior surface finish compared to the Ra < 5 nm cited, ensuring optimal homoepitaxial growth and reliable contact deposition. |
| Substrate Orientation | Standard (100) and custom orientations available. | Guaranteed precise crystallographic orientation for high-quality homoepitaxy. |
Engineering Support
Section titled “Engineering Support”6CCVD’s in-house team of PhD material scientists specializes in optimizing diamond properties for extreme applications. We offer consultation services to assist researchers in:
- Material Selection: Choosing the optimal SCD/BDD doping levels and thickness ratios for specific radiation detection projects (e.g., alpha, neutron, or high-flux environments).
- Process Optimization: Tailoring MPCVD growth recipes to maximize CCE and minimize point defects (like NV centers, which were noted in the paper’s PL spectra).
- Device Integration: Advising on metalization schemes and surface treatments necessary for robust, stable electrical contacts in high-energy physics modules.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
An advanced microwave plasma reactor ARDIS 300 was used to synthesize homoepitaxial structures of monocrystal diamond films at Project Center ITER. High-quality epitaxial diamond films were grown on boron-doped monocrystal diamond substrates using microwave plasma-assisted chemical vapor deposition from methane-hydrogen mixture. Structural and impurity perfection of diamond films were characterized by Raman spectroscopy, photoluminescence, and optical absorption. Prototypes of radiation detectors were created on the basis of grown diamond films with thickness 70-80 μm. The p-type substrate with boron concentration ~100 ppm served as an electrical contact. Detectors were irradiated by 5.5 MeV α-particles and 14.7 MeV neutrons, corresponding pulse height spectra were measured and detector sensitivities were determined. Charge collection efficiency for synthesized diamond was shown to achieve 94% and 91% when ~4 V/m electric field applied.