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	Commissariat à l’Énergie Atomique et aux Énergies Alternatives, Rudjer Boskovic Institute
Citations	22
Analysis	Full AI Review Included

Executive Summary

This study investigates the simultaneous effects of high temperature and high radiation on a synthetic single-crystal Chemical Vapor Deposition (sc-CVD) diamond detector, confirming its viability for extreme environments.

High-Temperature Stability: The sc-CVD diamond detector maintained stable spectroscopic performance up to 725 K (452 °C), achieving a Charge Collection Efficiency (CCE) of approximately 95% and an energy resolution of ≈2% (FWHM) in pristine regions across the entire tested temperature range.
Radiation Hardness Deterioration: In regions damaged by 5 MeV protons, the CCE exhibited an overall decrease with increasing temperature, indicating that the radiation hardness of diamond detectors deteriorates at elevated temperatures.
Thermal Recovery Observed: CCE in irradiated regions reached a minimum around 660 K, followed by saturation and subsequent recovery at higher temperatures, suggesting beneficial effects from thermally stimulated de-trapping and defect annealing.
Electrode Material Success: Tungsten (W) electrodes were successfully used, demonstrating thermal resilience and maintaining stable metal-semiconductor contact properties up to 725 K.
Low Field Sensitivity: The experiment used a very low electric field (0.092 V/µm), intentionally chosen to maximize sensitivity to radiation damage effects, confirming that higher fields (e.g., 0.37 V/µm at 434 K) are necessary to fully recover CCE in damaged areas.

Technical Specifications

Parameter	Value	Unit	Context
Maximum Operating Temperature	725	K	Highest temperature tested with stable spectroscopy.
Pristine CCE (Range)	94.2 to 95.8	%	Measured across 296 K to 725 K.
Energy Resolution (Stable)	~2.0 (40 keV FWHM)	%	Stable up to 660 K (using 2 MeV protons).
Energy Resolution (Max T)	2.64	%	Measured at 725 K.
Detector Material	sc-CVD Diamond	N/A	Electronic grade, <100> orientation, N concentration <5 ppb.
Detector Thickness	65	µm	Thinned for homogeneous defect distribution.
Electrode Material	Tungsten (W)	N/A	Sputtered, 200 nm thickness, 3 x 3 mm² area.
Damage Radiation Energy	5	MeV	Proton microbeam (used for selective damage).
Probing Radiation Energy	2	MeV	Proton microbeam (used for IBIC/CCE measurement).
Applied Electric Field (IBIC)	0.092	V/µm	Low field test condition (worst-case scenario).
Damage Fluence Range	3.8 x 10¹² to 2.2 x 10¹³	cm^-2	Total range across irradiated regions.
CCE Recovery Onset Temperature	~660	K	Temperature where CCE saturation/recovery begins in irradiated regions.
Field for 90% CCE Recovery (RT)	0.185	V/µm	Required field for lowest fluence region at 296 K.
Field for 90% CCE Recovery (434 K)	0.37	V/µm	Required field for lowest fluence region at 434 K.

Key Methodologies

The experiment utilized Ion Beam Induced Charge (IBIC) microscopy combined with controlled heating and proton irradiation to assess detector performance under extreme conditions.

Detector Fabrication: A 65 µm thick sc-CVD diamond was prepared. Tungsten (W) electrodes (200 nm) were sputtered onto the surfaces to ensure thermal stability of the metal-semiconductor contact at high temperatures.
Thermal Setup: The detector was mounted on a ceramic plate and heated by a resistive heater below a copper heat sink. Temperature was monitored using a Type K thermocouple, achieving stable operation up to 725 K.
Damage Introduction: A 5 MeV scanning proton microbeam was used to introduce localized radiation damage in small, defined areas (100 x 100 µm²). Two cycles of irradiation were performed, spanning fluences up to 2.2 x 10¹³ cm^-2.
Annealing Comparison: Cycle 1 regions were pre-annealed by heating the detector to 725 K for 30 minutes after irradiation. Cycle 2 regions were irradiated after cooling and were not pre-annealed, allowing comparison of thermal history effects.
Performance Probing (IBIC): The Charge Collection Efficiency (CCE) and energy resolution were mapped and measured using the IBIC technique with a 2 MeV proton microbeam. This energy provided a deep probe (24.5 µm range), ensuring both electron and hole contributions to the signal.
Low Electric Field Testing: All IBIC measurements were conducted at a low electric field (0.092 V/µm). This low bias condition was chosen to represent a “worst-case scenario” and maximize the visibility of charge trapping effects induced by radiation damage.
Electric Field Dependence Test: CCE measurements were repeated at room temperature (296 K) and 434 K while varying the electric field (up to 0.4 V/µm) to demonstrate the mitigation of radiation damage effects through increased bias voltage.

Commercial Applications

The demonstrated high-temperature and radiation-tolerant properties of sc-CVD diamond detectors are crucial for several demanding engineering sectors:

Nuclear and Fusion Energy: Essential for radiation monitoring and diagnostics within high-temperature environments, such as the core or immediate surroundings of fusion reactors (e.g., EUROfusion, ITER), where high neutron and particle fluxes are present.
High-Temperature Power Electronics: Diamond is a material of choice for developing next-generation power semiconductor devices (diodes, switching devices) that require operation at temperatures significantly higher than silicon or SiC, improving efficiency and reducing cooling requirements.
High-Energy Physics and Accelerators: Used as robust beam monitors, dosimeters, and particle detectors in accelerator facilities where components must withstand high radiation doses and thermal loads without degradation.
Space and Defense: Applications requiring sensors that maintain spectroscopic accuracy and stability under extreme thermal cycling and intense particle radiation fields encountered in space or military environments.
Industrial Process Monitoring: Sensing and control in harsh industrial environments (e.g., high-temperature furnaces, chemical processing) where conventional sensors fail due to heat or radiation exposure.

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]
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2019 - Data acquisition and control system for an evolving nuclear microprobe [Crossref]