High Resistivity and Low Defect Covalent Organic Frameworks for Highly Stable and Low Dose X-Ray Detection.

Area of Science:

• Materials Science
• Solid-State Physics
• Nanotechnology

Background:

• Conventional semiconductor materials for direct X-ray detection face challenges with charge-carrier signal extraction and mobile-metal-ion noise.
• Existing technologies often involve trade-offs between sensitivity and stability due to inherent material limitations.
• There is a need for advanced materials that can enhance X-ray attenuation and minimize electronic noise for improved detection.

Purpose of the Study:

• To demonstrate the first covalent organic framework (COF)-based direct X-ray detector.
• To investigate the potential of COF366-M, incorporating metal ions (Co, Cu), as an active layer for X-ray detection.
• To evaluate the performance, stability, and environmental friendliness of the novel COF-based detector.

Main Methods:

• Synthesized COF366-M (M = Co, Cu) with metal ions integrated into a porphyrin-centered crystalline framework.
• Incorporated carbon nanotubes (CNTs) to enhance charge separation and transport within the COF structure.
• Fabricated and tested the direct X-ray detector device under various X-ray doses and electric fields.

Main Results:

• The COF366-M active layer demonstrated enhanced X-ray attenuation and effectively suppressed ion migration, showing negligible current drift (∼10^-18 A·cm^-1·V^-1·s^-1).
• The detector achieved high sensitivity (up to 11,784 µC·Gy^-1·cm^-2), a low detection limit (39 nGy·s^-1), and excellent operational stability with no degradation after 148 Gy cumulative dose.
• The material exhibited high resistivity, low defect levels, and ordered nanochannels, suitable for efficient X-ray detection.

Conclusions:

• Covalent organic frameworks (COFs) represent a promising platform for developing high-performance, stable, and environmentally friendly direct X-ray detectors.
• The COF366-M material, with CNT integration, offers a molecular-level design strategy for next-generation low-dose radiation sensing.
• This work paves the way for advanced X-ray detection technologies with improved signal-to-noise ratios and intrinsic safety.