ELECTRON IRRADIATION OF AN UNDOPED HOMOEPITAXIAL DIAMOND TO SUPPRESS HOLE CONDUCTIVITY
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2025-06-20 |
| Journal | IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA |
| Authors | Vera O. Timoshenko, D. D. Prikhodko, С. А. Тарелкин, S. I. Zholudev, Nikolay V. Luparev |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Electron Irradiation for Hole Conductivity Suppression in SCD Diamond
Section titled “Technical Documentation & Analysis: Electron Irradiation for Hole Conductivity Suppression in SCD Diamond”This document analyzes the research paper “Electron Irradiation of an Undoped Homoepitaxial Diamond to Suppress Hole Conductivity” and outlines how 6CCVD’s advanced MPCVD diamond materials and fabrication services can support and extend this critical research in high-energy particle detection.
Executive Summary
Section titled “Executive Summary”This research successfully demonstrates a robust method for suppressing background hole conductivity in undoped homoepitaxial Single Crystal Diamond (SCD), a key limitation for high-energy particle detectors.
- Core Achievement: High-energy electron irradiation (3.5 MeV) effectively compensated residual boron impurities, reducing diamond conductivity by up to six orders of magnitude.
- Material Performance: Initial room temperature resistivity of ~5 kΩ·cm was increased beyond the measurement limit (> 10 GΩ·cm) across the entire 300 K to 1000 K temperature range.
- Compensation Mechanism: The irradiation creates deep vacancy-related centers (GR centers) that electrically compensate the shallow boron acceptors, neutralizing the background p-type conductivity.
- Thermal Stability: The compensated material exhibited exceptional thermal stability up to 1000 K, confirming the viability of high-temperature processing steps (e.g., 700 °C annealing for ohmic contacts).
- Detector Improvement: Post-irradiation ohmic contacts (Ti/Pt) achieved extremely low dark currents (< 1 nA at ±600 V), comparable to less stable Schottky contacts, significantly enhancing detector reliability and operational lifetime in extreme environments.
- 6CCVD Value: 6CCVD specializes in the high-purity SCD required for this application, offering custom dimensions, precise thickness control, and integrated metalization services (Ti/Pt/Au) to replicate and scale these high-stability detector structures.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the research detailing the material properties and experimental results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Material Type | Undoped Homoepitaxial | SCD | Grown via MPCVD (Plassys BJS 150) |
| Initial Boron Impurity Concentration | < 1014 | cm-3 | Background p-type conductivity source |
| Initial Resistivity (Room Temp) | ~5 to 6 | kΩ·cm | Before electron irradiation |
| Electron Irradiation Energy | 3.5 | MeV | Used for defect creation/compensation |
| Irradiation Dose (Low) | 2·1015 | cm-2 | Sample #1 |
| Irradiation Dose (High) | 1016 | cm-2 | Sample #2 |
| Resistivity Reduction | Up to 6 | Orders of magnitude | Post-irradiation at room temperature |
| Maximum Post-Irradiation Resistivity | > 10 | GΩ·cm | Measurement limit across 300-1000 K |
| Thermal Stability Range | Up to 1000 | K | No conductivity restoration observed |
| Detector Dark Current (Post-Irradiation) | < 1 | nA | Measured at ±600 V bias using ohmic contacts |
| Ohmic Contact Annealing Temperature | 700 | °C | Required for Ti/Pt contact formation |
| Sample Dimensions | 4 x 4 x 0.5 | mm | SCD plates used for testing |
Key Methodologies
Section titled “Key Methodologies”The experiment focused on high-purity SCD synthesis, controlled electron irradiation, and subsequent electrophysical characterization.
- CVD Synthesis: Undoped single-crystal diamond was grown homoepitaxially using a Plassys BJS 150 MPCVD system.
- Substrate Temperature: 850° ± 15 °C.
- Microwave Power: 2.7 kW.
- Gas Mixture: H2/CH4 ratio of 24/1.
- Gas Pressure: 180 ± 5 mbar.
- Growth Rate: ~1.5 - 2 µm/h.
- Sample Preparation: Square plates (4 x 4 x 0.5 mm) were cut from the synthesized SCD material.
- Contact Fabrication (Ohmic): For irradiated samples, ohmic contacts were prepared by magnetron sputtering of Titanium (Ti) and Platinum (Pt), followed by high-temperature annealing at 700 °C.
- Contact Fabrication (Schottky Reference): Non-irradiated samples used Schottky contacts, requiring a 650 °C anneal and subsequent surface treatment in SF6 plasma for 20 minutes prior to metal deposition.
- Electron Irradiation: Samples were exposed to high-energy electrons (3.5 MeV) at controlled doses (2·1015 cm-2 and 1016 cm-2) to induce deep compensating vacancy centers (GR centers).
- Electrophysical Characterization:
- Temperature-dependent resistivity and Hall effect measurements were performed using the Van der Pauw geometry (300 K - 1000 K, ±1 T magnetic field).
- Current-Voltage (I-V) characteristics were measured in a vertical detector geometry across a voltage range of -600 V to +600 V to determine dark current.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”This research highlights the critical need for ultra-high purity, thermally stable SCD material for advanced radiation detectors. 6CCVD is uniquely positioned to supply and process the required diamond components, offering integrated solutions from material growth to custom metalization.
| Research Requirement | 6CCVD Solution & Capability | Value Proposition for Engineers |
|---|---|---|
| Applicable Materials | High-Purity Optical Grade SCD (Single Crystal Diamond). Our MPCVD process ensures the lowest possible background impurity levels (< 1013 cm-3), providing the ideal starting material for subsequent electron compensation. | Guaranteed material purity and homogeneity, maximizing the effectiveness of the irradiation process and ensuring minimal dark current. |
| Custom Dimensions & Thickness | We provide SCD plates in custom dimensions, easily accommodating the 4 x 4 x 0.5 mm size used in the study. We offer SCD thicknesses from 0.1 µm up to 500 µm, and substrates up to 10 mm. | Seamless scalability from R&D prototypes to production volumes, with precise control over the active detector layer thickness. |
| Metalization & Contact Stability | Integrated Metalization Services: We offer in-house deposition of the required contact stack, including Ti, Pt, and Au. We can replicate the stable Ti/Pt ohmic contacts, ensuring optimal adhesion and thermal resilience up to 1000 K. | Eliminate external processing steps. Our expertise ensures mechanically and thermally stable contacts, crucial for detectors operating in extreme environments. |
| Polishing Requirements | SCD surfaces are polished to an industry-leading roughness of Ra < 1 nm. This pristine surface quality is essential for reliable, low-leakage Schottky and Ohmic contact formation. | Reduced surface leakage currents and improved contact uniformity, leading to lower detector noise and higher charge collection efficiency. |
| Engineering Support | 6CCVD’s in-house PhD team specializes in diamond electrophysics and can assist with material selection, optimizing growth parameters, and refining contact recipes for similar High-Energy Particle Detector projects requiring conductivity compensation. | Access to expert consultation to accelerate development and ensure material specifications meet demanding operational requirements. |
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The use of undoped single-crystal diamond as material for the manufacture of detectors for high-energy particles and various types of ionizing radiation is limited by background conductivity caused by boron impurities, leading to high dark currents in such metal-semiconductor-metal or metal-dielectric-metal structures. This study explores the possibility of reducing background conductivity in undoped homoepitaxial diamond through irradiation with low doses of high-energy electrons (3,5 MeV). We studied single-crystal diamonds with impurity concentrations below 1014 cm-3 nevertheless demonstrating resistivity of ~5 kΩ∙cm at room temperature. The samples were irradiated with electron doses of ~2∙1015 cm-2 and ~1016 cm-2. The results were monitored by analyzing the temperature dependence of the material’s electrophysical properties and the current-voltage characteristics of detector samples made from it. The obtained results show that irradiation effectively reduces diamond conductivity by several orders of magnitude. Studies of the temperature dependences of electrophysical parameters confirm the material’s stability after irradiation in the temperature range up to 1000 K, enabling the fabrication of ohmic contacts in detector structures without degradation of their characteristics. Measurements of current-voltage characteristics demonstrate a significant reduction in the dark current of a detector after irradiation. Moreover, the dark current of the irradiated samples with ohmic contacts, which exhibit enhanced mechanical and thermal stability, is comparable to that of non-irradiated samples with Schottky contacts. The obtained data open prospects for developing homoepitaxial diamond-based detectors resistant to extreme operating conditions. For citation: Timoshenko V.O., Prikhodko D.D., Tarelkin S.A., Zholudev S.I., Luparev N.V., Kornilov N.V. Electron irradiation of an undoped homoepitaxial diamond to suppress hole conductivity. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2025. V. 68. N 9. P. 53-59. DOI: 10.6060/ivkkt.20256809.12y.