Thallium Bromide Semiconductor Radiation Detectors

Thallium bromide (TlBr) is an ionic semiconductor distinguished by a wide band gap of 2.68 eV, high atomic numbers (Tl = 81, Br = 35) and a density of 7.56 g cm⁻³, attributes that yield exceptional gamma-ray attenuation and low thermal noise at room temperature. Advances in crystal growth and purification have raised the electron mobility-lifetime product to the order of 10⁻² cm² V⁻¹, enabling thick, high-resolution detectors comparable to cadmium zinc telluride. Practical implementations encompass planar devices, pixel arrays and Frisch-collar geometries. Key challenges include ionic polarisation under bias, which disrupts charge collection and provokes electrode degradation, and the need for defect-free metal-semiconductor interfaces. Through combined efforts in crystal characterisation, interface engineering and bias-management techniques, TlBr detectors have moved towards stable, long-lived operation for applications in medical imaging, homeland security and fundamental physics.

Research from Nature Portfolio

Recent studies have employed neutron Bragg-dip imaging alongside pulsed-laser time-of-flight methods to map spatial distributions of crystal orientation and carrier mobility within TlBr ingots. These analyses demonstrate that, at present impurity levels, chemical contaminants exert a more significant effect on charge transport than grain-boundary density, informing targeted purification protocols. Concurrently, the application of novel electrode materials and engineered interfaces has produced virtually defect-free contacts. Pixelated TlBr detectors with these interfaces exhibit minimal noise and maintain spectral stability within ±1% over several thousand hours at room temperature, marking a substantial advance towards reliable field-deployed spectrometers.

Thallium Bromide Semiconductor Radiation Detectors publication trend

The graph below shows the total number of articles in thallium bromide semiconductor radiation detectors across all publications each year (not limited to Nature Index journals).

Technical terms

Band gap: Energy difference between the valence and conduction bands that determines the detector’s photon absorption threshold.

Charge carrier mobility: Measure of how quickly electrons or holes move through the semiconductor under an electric field.

Polarisation: Migration and accumulation of ionic species in the crystal under bias, which degrades the internal electric field.

Mobility-lifetime product (μτ): Combined figure of merit of carrier mobility and lifetime that dictates charge collection efficiency.

Bragg-dip imaging: Neutron-based technique for visualising crystal orientation and imperfections within bulk materials.

References

1. Stable room-temperature thallium bromide semiconductor radiation detectors. APL Materials (2017).
2. Comparison between carrier transport property and crystal quality of TlBr semiconductors. Scientific Reports (2024).
3. Novel Electrodes and Engineered Interfaces for Halide-Semiconductor Radiation Detectors. Scientific Reports (2019).
4. Thallium Bromide Gamma-Ray Spectrometers and Pixel Arrays. Frontiers in Physics (2020).