Technology Commercialization and Partnerships | BSA 12-23: Surface Treatment of CZT Crystals for Passivation and Protection

Category: electronics & instrumentation

BSA 12-23: Surface Treatment of CZT Crystals for Passivation and Protection

BNL Reference Number: BSA 12-23

Patent Status: U.S. Patent Number 6,043,106 was issued on March 28, 2000

Summary

This invention comprises a method for reducing the leakage current in CZT crystals, particularly Cd(1-x)Zn(x)Te crystals (where x is greater than equal to zero and less than or equal to 0.5), and preferably Cd(0.9)Zn(0.1) Te crystals, thereby enhancing the ability of these crystal to spectrally resolve radiological emissions from a wide variety of radionuclides. Two processes are disclosed. The first method provides for depositing, via reactive sputtering, a silicon nitride hard-coat overlayer which provides significant reduction in surface leakage currents. The second method enhances the passivation by oxidizing the CZT surface with an oxygen plasma prior to silicon nitride deposition without breaking the vacuum state.

Description

CdZnTe (CZT) crystals, particularly Cd(1-x)Zn(x)Te (where x is greater than or equal to zero and less than 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 provides a method for surface treatment of CZT crystals that reduces surface leakage currents to a previously unattainable level and simultaneously provides a hard-coat over-layer which should prevent performance decay over time due to exposure to moisture and other gases in the working environment thereby providing for improved energy resolution and reliability. This invention involves two processes. These processes follow either a traditional bromine-methanol etch treatment or an improved wet etch consisting of a solution containing HBr, ethylene glycol, and bromine in ratios of approximately 10: 10: 1 with a ±20% variation in these concentrations. These results have been found to be improved still further by rinsing the etch crystal in pure ethylene glycol immediately following the etch process.

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.