A Study of the Radiation Tolerance and Timing Properties of 3D Diamond Detectors

At a Glance

Metadata	Details
Publication Date	2022-11-11
Journal	Sensors
Authors	L. Anderlini, Marco Bellini, V. Cindro, C. Corsi, K. Kanxheri
Institutions	University of Siegen, Istituto Nazionale di Fisica Nucleare
Citations	3
Analysis	Full AI Review Included

Technical Documentation & Analysis: 3D Diamond Detectors for Extreme Environments

Source Paper: A Study of the Radiation Tolerance and Timing Properties of 3D Diamond Detectors (Sensors 2022, 22, 8722)

Executive Summary

This research validates the superior performance of 3D Single Crystal Diamond (SCD) detectors fabricated via laser engineering, confirming their suitability for next-generation high luminosity particle physics experiments (e.g., HL-LHC).

Extreme Radiation Hardness: Demonstrated operational stability and sustained Charge Collection Efficiency (CCE) up to neutron fluences of 1.0 x 10¹⁶ n/cm² (1 MeV equivalent).
Enhanced Architecture: The 3D columnar electrode design significantly increases radiation tolerance compared to traditional planar detectors, with performance improving proportionally to electrode density (up to 500 col/mm²).
High Temporal Resolution: Achieved a temporal resolution of 82 ± 2 ps in beam tests (180 GeV pions) using optimized 3D SCD structures, approaching the performance limits of solid-state timing detectors.
Defect Passivation: High fluence irradiation resulted in a significant increase in the maximum applicable bias voltage (up to 640 V), attributed to the passivation of defects within the diamond bulk.
Advanced Fabrication: Devices were manufactured using precise femtosecond (fs) laser micro-machining for bulk column creation and nanosecond (ns) laser graphitization for surface interconnection on electronic grade SCD plates.
Material Quality: The use of high-purity, electronic grade SCD (with <1 ppb impurities) was critical to achieving near 100% CCE in unirradiated planar configurations.

Technical Specifications

The following hard data points were extracted from the experimental results and simulations, highlighting the performance metrics of the 3D SCD detectors.

Parameter	Value	Unit	Context
Base Material	SCD (Electronic Grade CVD)	N/A	Monocrystalline diamond plate
Nominal Thickness	500	µm	Sample thickness used for 3D fabrication
Maximum Neutron Fluence	1.0 x 10¹⁶	n/cm²	Highest fluence tested (1 MeV equivalent)
Temporal Resolution (Strip)	82 ± 2	ps	Achieved in 180 GeV pion beam test
Asymptotic Resolution (Fitted)	72	ps	Predicted resolution for large signals
Unit Cell Dimensions (Timing)	55 x 55	µm	Pitch of the 3D pixel structure
Electrode Density (Highest Tolerance)	500	col/mm²	Demonstrated highest radiation tolerance
Maximum Bias Voltage (Irradiated)	640	V	Applicable bias after 5.0 x 10¹⁵ n/cm² fluence
CCE (Unirradiated Planar)	~95%	N/A	Measured at 200 V bias
Optimized Column Resistance	~30	kΩ	Achieved post-laser fabrication optimization
Damage Constant (k)	(1.5 ± 0.15) x 10^-6	cm² s^-1	Used for CCE decay modeling

Key Methodologies

The fabrication and testing relied on highly specialized CVD material and advanced laser processing techniques, demonstrating the complexity of 3D detector manufacturing.

Material Selection: Use of synthetic “electronic grade” scCVD diamond plates (4.5-5 x 4.5-5 mm², 500 µm nominal thickness) with high purity (<1 ppb impurities).
Bulk Electrode Fabrication: Columnar electrodes were written into the diamond bulk using a femtosecond (fs) Ti: Sa laser (800 nm, ~50 fs pulse duration) via multi-photon excitation, inducing a phase transition from sp³ (diamond) to sp² (graphitic/conductive mixture).
Surface Interconnection: A nanosecond (ns) Nd: YAG laser (1064 nm, 8 ns) was used for surface graphitization to connect the bulk columnar electrodes into interpenetrating bias and signal matrices.
Radiation Exposure: Samples were irradiated with fast neutrons at the Triga reactor (Ljubljana), with fluences normalized to 1 MeV equivalent, up to 1.0 x 10¹⁶ n/cm².
CCE Measurement: Charge Collection Efficiency was measured using a Sr-90 beta source setup, with frequent bias voltage reversal and priming procedures to mitigate polarization effects.
Timing Measurement: Temporal resolution was determined using both laboratory setups (Sr-90 source, MCP-PMT reference) and beam tests (180 GeV pions at CERN), recorded via high-speed oscilloscopes (6 GHz, 40 Gs/s) and analyzed using Constant Fraction Discrimination (CFD).

6CCVD Solutions & Capabilities

The successful replication and advancement of this high-performance 3D diamond detector technology require materials and processing capabilities that align perfectly with 6CCVD’s core offerings. We provide the foundation necessary for engineers and scientists to push the boundaries of radiation-hard timing sensors.

Applicable Materials

To replicate or extend this research, 6CCVD recommends the following materials:

Optical Grade Single Crystal Diamond (SCD): Essential for achieving the near-100% CCE baseline required for high-speed timing. Our SCD material ensures the minimum presence of defects and impurities (<1 ppb), crucial for maintaining performance under extreme radiation.
Custom SCD Substrates: While the paper used 500 µm thickness, 6CCVD can supply SCD plates with precise thickness control from 0.1 µm up to 500 µm, and substrates up to 10 mm, allowing optimization of charge generation depth for specific MIP detection requirements.

Customization Potential

The 3D architecture relies heavily on precise laser processing and low-resistance contacts. 6CCVD offers comprehensive services to meet these demanding specifications:

Research Requirement	6CCVD Customization Service	Technical Advantage
3D Architecture Fabrication	Advanced Laser Machining: High-precision fs and ns laser processing capabilities for bulk modification and surface graphitization.	Enables the creation of complex 3D columnar geometries (e.g., 55 µm pitch) and optimization of electrode resistance (currently 30 kΩ, aiming for 1 kΩ).
Custom Dimensions	Large Area PCD/SCD: While the paper used small samples (4.5 x 4.5 mm²), 6CCVD provides PCD plates up to 125 mm in diameter, facilitating the development of larger pixel tracking systems.	Supports scaling from R&D prototypes to full-scale pixel detectors for high luminosity experiments.
Electrode Contact Optimization	In-House Metalization: Deposition of high-quality contacts using Au, Pt, Pd, Ti, W, or Cu.	Critical for reducing signal rise time and improving S/N ratio, directly impacting the achievable temporal resolution (82 ps).
Surface Quality	Ultra-Precision Polishing: SCD polishing to achieve surface roughness Ra < 1 nm.	Necessary for high-quality optical access during laser fabrication and minimizing surface leakage currents.

Engineering Support

6CCVD’s in-house PhD team specializes in the physics of CVD diamond detectors, including radiation damage modeling (using parameters like the damage constant k) and high-speed charge transport dynamics. We can assist researchers in:

Material Selection: Determining the optimal SCD grade and thickness for specific neutron or proton fluence requirements.
Geometry Optimization: Consulting on the ideal 3D unit cell pitch and electrode density to maximize radiation tolerance and timing performance for similar High Luminosity Particle Physics projects.
Simulation Validation: Providing material parameters necessary for accurate Monte Carlo and finite element simulations (e.g., KDetSim, Sentaurus TCAD) used in 3D detector design.

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

View Original Abstract

We present a study on the radiation tolerance and timing properties of 3D diamond detectors fabricated by laser engineering on synthetic Chemical Vapor Deposited (CVD) plates. We evaluated the radiation hardness of the sensors using Charge Collection Efficiency (CCE) measurements after neutron fluences up to 1016 n/cm2 (1 MeV equivalent.) The radiation tolerance is significantly higher when moving from standard planar architecture to 3D architecture and increases with the increasing density of the columnar electrodes. Also, the maximum applicable bias voltage before electric breakdown increases significantly after high fluence irradiation, possibly due to the passivation of defects. The experimental analysis allowed us to predict the performance of the devices at higher fluence levels, well in the range of 1016 n/cm2. We summarize the recent results on the time resolution measurements of our test sensors after optimization of the laser fabrication process and outline future activity in developing pixel tracking systems for high luminosity particle physics experiments.

Tech Support

Original Source

DOI: https://doi.org/10.3390/s22228722

References

2022 - Recent progress in diamond radiation detectors [Crossref]
2021 - Diamond Detectors for Radiotherapy X-Ray Small Beam Dosimetry [Crossref]
2021 - Properties of diamond-based neutron detectors operated in harsh environments [Crossref]
2021 - Progress in semiconductor diamond photodetectors and MEMS sensors [Crossref]
2019 - Recent progress in solar-blind deep-ultraviolet photodetectors based on inorganic ultrawide bandgap semiconductors [Crossref]
2021 - Charge transport in single crystal CVD diamond studied at high temperatures [Crossref]