Characterization of Thick Selenium Layers for Dual-Layer X-ray Imaging

Area of Science:

• Medical Physics
• Materials Science
• X-ray Imaging Technology

Background:

• Amorphous selenium (a-Se) is a direct conversion X-ray photoconductor with excellent properties for X-ray imaging.
• Thick a-Se layers are being explored for cost-effective dual-layer X-ray flat-panel detectors (DL-FPDs).

Purpose of the Study:

• To fabricate and evaluate thick amorphous selenium layers for DL-FPDs.
• To investigate the impact of a-Se layer thickness on detector performance, including dark current, photoresponse, and temporal lag.

Main Methods:

• Manufactured 253 μm and 414 μm a-Se samples with polyimide hole-blocking contacts.
• Measured dark current suppression below 10 pA/mm² at electric fields up to 10 V/μm.
• Evaluated photoresponse under low-energy X-ray irradiation and analyzed temporal lag.

Main Results:

• Both fabricated a-Se layers exhibited low dark current.
• The 414 μm a-Se layer showed higher photocurrent due to increased photon absorption.
• Thicker a-Se samples displayed more signal persistence at lower bias, indicating increased carrier trapping.

Conclusions:

• Thick a-Se layers are viable for DL-FPDs, offering improved photon absorption.
• Layer thickness influences carrier trapping and signal persistence, requiring careful consideration for readout electronics design.
• These findings provide critical metrics for optimizing future direct/indirect DL-FPD designs.