Electronic Properties of a Synthetic Single-Crystal Diamond Exposed to High Temperature and High Radiation

At a Glance

Metadata	Details
Publication Date	2020-05-29
Journal	Materials
Authors	Andreo Crnjac, N. Skukan, G. Provatas, M. Rodríguez-Ramos, M. Pomorski
Institutions	CEA LIST, Commissariat à l’Énergie Atomique et aux Énergies Alternatives
Citations	22
Analysis	Full AI Review Included

Electronic Properties of High-Temperature, Radiation-Hard Single-Crystal Diamond

6CCVD Technical Analysis & Sales Documentation Reference: Crnjac et al., Materials 2020, 13, 2473

Executive Summary

This research validates the superior performance of synthetic Single-Crystal Diamond (SCD) detectors under extreme combined conditions of high temperature and intense radiation, confirming diamond’s role as the material of choice for next-generation fusion reactors and accelerator facilities.

Extreme Operating Range: SCD detectors maintained excellent spectroscopic properties up to 725 K (452 °C), significantly exceeding the operational limits of conventional semiconductors like silicon.
Stable Performance: Charge Collection Efficiency (CCE) remained stable at approximately 95% across the entire 296 K to 725 K temperature range in pristine (unirradiated) regions.
High Resolution: Energy resolution (FWHM) remained constant at 2.0% (40 keV FWHM) up to 660 K, demonstrating suitability for high-precision spectroscopic applications.
Radiation Hardness: The detector was exposed to 5 MeV proton fluences up to 2.2 x 10¹³ cm^-2, showing resilience even under low electric field conditions (0.092 V/µm).
Thermal Recovery Mechanism: A critical finding was the saturation and recovery of CCE in irradiated regions above 660 K, suggesting thermally stimulated de-trapping and defect annealing counteracting radiation damage.
Material Focus: The study highlights the necessity of using high-purity, electronic-grade sc-CVD diamond with thermally stable metalization (Tungsten) for reliable high-temperature device fabrication.

Technical Specifications

The following hard data points were extracted from the experimental results, demonstrating the robust performance metrics achieved by the sc-CVD diamond detector:

Parameter	Value	Unit	Context
Material Type	sc-CVD Diamond	N < 5 ppb	Electronic Grade, <100> Orientation
Detector Thickness	65	µm	Thinned via laser slicing and polishing
Electrode Material	Tungsten (W)	200 nm	Sputtered, 3 x 3 mm² area
Maximum Operating Temperature	725	K	Highest temperature tested (452 °C)
Pristine CCE (Range)	94.2 - 95.8	%	Stable across 296 K to 725 K
Energy Resolution (Stable)	2.0	%	FWHM, stable up to 660 K (2 MeV protons)
Energy Resolution (Max Temp)	2.64	%	FWHM measured at 725 K
Damaging Radiation Energy	5	MeV	Proton microbeam
Maximum Deposited Fluence	2.2 x 10¹³	cm^-2	High Fluence region (Cycle 1)
Applied Electric Field (IBIC)	0.092	V/µm	Low field chosen to maximize sensitivity to damage
CCE Recovery Onset	> 660	K	Observed saturation/recovery in irradiated regions

Key Methodologies

The experimental success relied on precise material preparation and specialized high-temperature testing protocols, which 6CCVD is uniquely positioned to support.

Material Selection and Thinning:
- Electronic grade sc-CVD diamond (N < 5 ppb) was selected for its high purity and wide band-gap properties.
- The material was thinned to 65 µm to optimize defect distribution homogeneity under MeV proton irradiation.
High-Temperature Metalization:
- Thermally stable 200 nm Tungsten (W) electrodes were sputtered onto the diamond surfaces to ensure the metal-semiconductor contact integrity at elevated temperatures.
High-Temperature Mounting:
- The metallized diamond was mounted onto a ceramic plate using high-temperature silver paste, heated by a resistive heater below a copper heat sink.
Selective Radiation Damage:
- A 5 MeV scanning proton microbeam was used in high-current mode (1-10 pA) to selectively introduce damage in small, localized 100 x 100 µm² regions.
Spectroscopic Characterization (IBIC):
- The Ion Beam Induced Charge (IBIC) technique, using a 2 MeV proton microbeam in low-current mode (<fA), was employed to monitor CCE and energy resolution changes across pristine and damaged regions simultaneously.
Thermal Testing:
- The detector was tested across a wide range of temperatures (296 K to 725 K), including a high-temperature annealing step (725 K) applied to the Cycle 1 irradiated regions.

6CCVD Solutions & Capabilities

This research confirms that the intrinsic properties of high-purity MPCVD diamond are ideal for extreme environment sensing, provided the material specifications and device integration (metalization, thickness) are optimized for thermal resilience. 6CCVD offers the necessary custom materials and engineering services to replicate and advance this critical research.

Applicable Materials

To achieve the high CCE stability and spectroscopic resolution demonstrated in this paper, 6CCVD recommends the following materials:

Optical Grade SCD (Single Crystal Diamond): Equivalent to the electronic grade material used, featuring nitrogen concentration typically below 5 ppb. This ensures minimal intrinsic defects and maximum charge carrier mobility required for high-temperature radiation detection.
Custom SCD Thickness: The paper utilized a 65 µm thick sample. 6CCVD routinely provides SCD plates/wafers with custom thicknesses ranging from 0.1 µm up to 500 µm, polished to Ra < 1 nm, allowing researchers to precisely tune detector depth for specific MeV particle ranges.

Customization Potential

The limiting factor identified in the paper was the thermal resilience of the device components (metalization, mounting). 6CCVD specializes in custom fabrication solutions to overcome these integration challenges:

Requirement from Paper	6CCVD Capability	Benefit to Customer
Thermally Stable Electrodes	Custom Metalization Services	We offer sputtering and deposition of high-temperature metals including Tungsten (W), Platinum (Pt), Titanium (Ti), and Gold (Au), ensuring contact stability up to 725 K and beyond.
Specific Detector Area	Custom Dimensions & Laser Cutting	We provide plates/wafers up to 125 mm (PCD) and offer precise laser cutting and shaping services to produce the required 3 x 3 mm² detector areas with high accuracy.
High-Purity Substrates	SCD Substrates up to 10 mm	For robust, high-temperature mounting solutions, 6CCVD can supply thick SCD substrates (up to 10 mm) for superior thermal management and heat sinking.
Surface Finish	Ultra-Low Roughness Polishing	SCD polishing to Ra < 1 nm minimizes surface defects that can contribute to charge trapping and polarization effects, critical for maintaining high CCE.

Engineering Support

6CCVD’s in-house PhD team provides expert consultation to assist researchers and engineers in designing high-temperature radiation detectors:

Material Selection: Guidance on selecting the optimal diamond grade (SCD vs. PCD, doping levels) based on specific radiation type (protons, neutrons, gamma) and operating temperature requirements.
Device Architecture: Support in optimizing electrode geometry and selecting appropriate metalization schemes for applications requiring operation above 725 K, where thermal stability is paramount.
Radiation Hardness Extension: Assistance in designing experiments to test the effect of higher electric fields (as suggested in Figure 5 of the paper) on CCE recovery and radiation tolerance at elevated temperatures.

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

View Original Abstract

Diamond, as a wide band-gap semiconductor material, has the potential to be exploited under a wide range of extreme operating conditions, including those used for radiation detectors. The radiation tolerance of a single-crystal chemical vapor deposition (scCVD) diamond detector was therefore investigated while heating the device to elevated temperatures. In this way, operation under both high-temperature and high-radiation conditions could be tested simultaneously. To selectively introduce damage in small areas of the detector material, a 5 MeV scanning proton microbeam was used as damaging radiation. The charge collection efficiency (CCE) in the damaged areas was monitored using 2 MeV protons and the ion beam induced charge (IBIC) technique, indicating that the CCE decreases with increasing temperature. This decreasing trend saturates in the temperature range of approximately 660 K, after which CCE recovery is observed. These results suggest that the radiation hardness of diamond detectors deteriorates at elevated temperatures, despite the annealing effects that are also observed. It should be noted that the diamond detector investigated herein retained its very good spectroscopic properties even at an operation temperature of 725 K (≈2% for 2 MeV protons).

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma13112473

References

2007 - Radiation hardness of diamond and silicon sensors compared [Crossref]
2016 - The evaluation of radiation damage parameter for CVD diamond [Crossref]
2019 - Enhanced radiation hardness and signal recovery in thin diamond detectors [Crossref]
2015 - High-temperature characteristics of charge collection efficiency using single CVD diamond detectors [Crossref]
2017 - Diamond detectors for high-temperature transactinide chemistry experiments [Crossref]
2019 - High temperature response of a single crystal CVD diamond detector operated in current mode [Crossref]
2018 - Recent advances in diamond power semiconductor devices [Crossref]
2019 - Data acquisition and control system for an evolving nuclear microprobe [Crossref]