Cadmium zinc telluride
Cadmium zinc telluride, (CdZnTe) or CZT, is a compound of cadmium, zinc and tellurium or, more strictly speaking, an alloy of cadmium telluride and zinc telluride. A direct bandgap semiconductor, it is used in a variety of applications, including radiation detectors, photorefractive gratings, electro-optic modulators, solar cells, and terahertz generation and detection. The band gap varies from approximately 1.4 to 2.2 eV, depending on composition.
Radiation detectors using CZT can operate in direct-conversion (or photoconductive) mode at room temperature, unlike some other materials (particularly germanium) which require liquid nitrogen cooling. Their relative advantages include high sensitivity for x-rays and gamma-rays, due to the high atomic numbers of Cd and Te, and better energy resolution than scintillator detectors. CZT can be formed into different shapes for different radiation-detecting applications, and a variety of electrode geometries, such as coplanar grids and small pixel detectors, have been developed to provide unipolar (electron-only) operation, thereby improving energy resolution.
The material has a high electro-optic coefficient and transparency in the mid-infrared region, making it a good modulator material for infrared lasers. The same properties make it useful for detection of terahertz waves.
An additional use is as a substrate material for the epitaxial growth of mercury cadmium telluride (HgCdTe), an infrared detector material. Cd0.96Zn0.04Te is almost perfectly lattice matched to LWIR HgCdTe (80% Hg, 20% Cd). However, it is difficult to grow large crystals of fixed composition.
Cadmium Zinc Telluride as a compound was found to be non-toxic at 5g/1 kg in an "Acute Oral Limit Toxicity Study" conducted by Toxikon
- "Small pixel CZT detector for hard X-ray spectroscopy". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
- "Pixellated Cd(Zn)Te high-energy X-ray instrument". IOP Journal of Instrumentation.
- The test was initiated on March 9, 1993 by II-VI Inc. and it was performed according to Federal Hazardous Substances Act, 16CFR, Part 1500.3, January 1990.
- Properties of Narrow-Gap Cadmium-Based Compounds Ed. P. Capper (INSPEC, IEE, London, UK, 1994) ISBN 0-85296-880-9
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