Technology Commercialization and Partnerships | BSA 12-22: Surface Treatment of CZT Crystals

Category: electronics & instrumentation

BSA 12-22: Surface Treatment of CZT Crystals

BNL Reference Number: BSA 12-22

Patent Status: U.S. Patent Number 5,933,706 was issued on August 3, 1999

Summary

A method for treatment of the surface of a CdZnTe (CZT) crystal that reduces surface roughness (increases surface planarity) and provides an oxide coating to reduce surface leakage currents and thereby, improve resolution. A two step process is disclosed, etching the surface of a CZT crystal with a solution of lactic acid and bromine in ethylene glycol, following the conventional bromine/methanol etch treatment, and after attachment of electrical contacts, oxidizing the CZT crystal surface.

Description

CdZnTe (CZT) crystals, particularly Cd(1-x)Zn(x)Te (where x is less or equal 0.5) crystals and preferably Cd(0.9)Zn(0.1)Te crystals, are useful for fabrication of small, portable, room temperature radiation detectors. This invention involves a method for surface treatment of CZT crystals that reduces surface roughness (increases surface planarity) and provides a coating on the surface of the CZT crystal to reduce surface leakage currents to a previously unattainable level, thereby providing for improved energy resolution. This method involves a two step process, wherein the surface of a CZT crystal is etched with a solution of lactic acid and bromine in ethylene glycol, following the traditional bromine/methanol etch treatment, and after attachment of electrical contacts the surface of the CZT crystal is oxidized, preferably by treatment with a solution of hydrogen peroxide.

Benefits

This method for reduction of the surface leakage current in CZT crystals improves spectral resolution to a level previously unattainable using prior art methods.

Applications and Industries

Semiconductor radiation detectors are now used in a large variety of fields, including nuclear physics, X-ray and gamma ray astronomy, and nuclear medicine. Their imaging capabilities, good energy resolution, and the ability to fabricate compact systems are very attractive features, in comparison with other types of detectors, such as gas detectors and scintillators. Medical, imaging, nuclear nonproliferation, non-destructive detection, radiation imaging, and homeland security applications.