Fine-scale spatial response of CdZnTe radiation detectors

Brunett, B. A.; Scyoc, J. M. Van; Hilton, Nathan R.; Lund, J.C.; James, R. B.; Schlesinger, T. E.

doi:10.1109/23.775521

Cited by 13 publications

(6 citation statements)

References 5 publications

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“…In high-quality detectors, small defects are less likely to cause a large loss in performance when a large area of the crystal is being used as the detector. However, when high-spatial-resolution gamma detection is desired even small defects cause a noticeable decrease in performance [14][15][16][18][19]. A common defect found in most high-quality CZT crystals is Te secondary phases, often located along grain boundaries [13,16,19,24,25].…”

Section: Introductionmentioning

confidence: 99%

Synchrotron radiation x-ray absorption fine-structure and Raman studies on CdZnTe ternary alloys

Chen

Feng

et al. 2009

SPIE Proceedings

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The synchrotron radiation (SR) X-ray absorption fine-structure spectroscopy (XAFS) technology has been employed to obtained Zn K-edge absorption spectra for Cd 1−x Zn x Te alloy with x = 0.03, 0.10, 0.20, 0.30, 0.40, 0.50 and 1.00. Their Fourier transform spectra were analyzed, which have shown a bimodal distribution of bond lengths, suggesting distortion of the Te sub-lattice, so that the linear interpolation is true only in an approximate sense. Synthetic CdZnTe crystals can be used for the room temperature-based detection of gamma radiation. The radiation detection properties of CZT crystals vary widely. A common defect found in most high-quality CZT crystals is Te secondary phases, often located along grain boundaries. The secondary phases can be both large inclusions (>50 μm) and smaller precipitates (<50 μm). The Te secondary phases distributed throughout the crystal can cause changes to the detector leakage current, resulting in decreased radiation spectrometer performance. This set of Cd 1-x Zn x Te crystals were also measured by Raman scattering at room temperature. The two observed peaks at about 125 and 145 cm -1 which can be assigned to Te A 1 and E phonon mode, respectively. The induced damage on the crystal surfaces by Raman laser has been discussed. It is suggested that in the case of highly Zn doping CdZnTe crystals, the ZnTe bond were broken by laser exposing and then free Te atoms are migrating to these heated areas which cause Te precipitate. Further, the results of the soft X-ray measurements have been also presented and this part of the experimental data needs to do more penetrating analysis in the future.

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Section: Introductionmentioning

confidence: 99%

Synchrotron radiation x-ray absorption fine-structure and Raman studies on CdZnTe ternary alloys

Chen

Feng

et al. 2009

SPIE Proceedings

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“…[14][15][16][17] In Fig. 8, a gamma response map, a transmission IR map, and topographs of a 27 mm ϫ 27 mm ϫ 2 mm CZT crystal are shown.…”

Section: Resultsmentioning

confidence: 99%

High-energy X-ray diffraction and topography investigation of CdZnTe

Carini

Camarda

Zhong

et al. 2005

Journal of Elec Materi

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High-energy transmission x-ray diffraction techniques have been applied to investigate the crystal quality of CdZnTe (CZT). CdZnTe has shown excellent performance in hard x-ray and gamma detection; unfortunately, bulk nonuniformities still limit spectroscopic properties of CZT detectors. Collimated high-energy x-rays, produced by a superconducting wiggler at the National Synchrotron Light Source's X17B1 beamline, allow for a nondestructive characterization of thick CZT samples (2-3 mm). In order to have complete information about the defect distribution and strains in the crystals, two series of experiments have been performed. First, a monochromatic 67 keV x-ray beam with the size of 300 ϫ 300 µm 2 was used to measure the rocking curves of CZT crystals supplied by different material growers. A raster scan of a few square centimeter area allowed us to measure the full-width at half-maximum (FWHM) and shift in the peak position across the crystal. The rocking curve peak position and its FWHM can be correlated with local stoichiometry variations and other local defects. Typically, the FWHM values ranging from 8.3 arcsec to 14.7 arcsec were measured with the best crystal used in these measurements. Second, transmission white beam x-ray topography (WBXT) was performed by using a 22 mm ϫ 200 µm beam in the energy range of 50 keV to 200 keV. These types of measurements allowed for large area, high-resolution (50 µm) scans of the samples. Usually, this technique is used to visualize growth and process-induced defects, such as dislocations, twins, domains, inclusions, etc. the difference in contrast shows different parts of the crystal that could not be shown otherwise. In topography, good contrast is indicative of a high quality of the sample, while blurred gray shows the presence of defects. Correlation with other techniques (e.g., infrared (IR) mapping and gamma mapping) was also attempted. Our characterization techniques, which use highly penetrating x-rays, are valid for in-situ measurements, even after electrical contacts have been formed on the crystal in a working device. Thus, these studies may lead to understanding the effects of the defects on the device performance and ultimately to improving the quality of CZT material required for device fabrication. It is important to study crystals from different ingot positions (bottom, center, and top); consequently, more systematic studies involving scans from center to border are planned.

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“…Several groups have used the microscale characterization technique for detailed investigations of the spatial response of CZT detectors. [7][8][9] In this work, we took advantage of synchrotron radiation to investigate the detectorsÕ surface region; this method affords us a spatial resolution as low as 10 lm and tunable X-ray energy. We irradiated the detector with various degrees of surface roughness with a high-spatialresolution X-ray beam of 10 keV to 20 keV energy generated at BrookhavenÕs national synchrotron light source.…”

Section: Introductionmentioning

confidence: 99%

Effects of Surface Processing on the Response of CZT Gamma Detectors: Studies with a Collimated Synchrotron X-Ray Beam

Hossain

Bolotnikov

Camarda

et al. 2008

Journal of Elec Materi

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Using a microscale X-ray mapping technique incorporating a synchrotron beam, we are able to reveal the fine details of the surface properties in cadmium zinc telluride (CZT) semiconductor detectors. A detector, with various degrees of surface roughness, was irradiated by a high-spatial-resolution X-ray beam. The detectorÕs response was analyzed and displayed as a twodimensional (2-D) map, and the charge collection was obtained from the peak positions in the spectra versus the beamÕs location, which reflects the local material properties. We noted the correlation between the 2-D image and the spectral response of the charge collection at different locations on the surface area, which indicates that a rough surface tends to contain trapping centers, thereby enhancing leakage current and distorting the signal. We also discuss our observations on the transition effect at the boundary area of a rough and a smooth surface under identical conditions.

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Fine-scale spatial response of CdZnTe radiation detectors

Cited by 13 publications

References 5 publications

Synchrotron radiation x-ray absorption fine-structure and Raman studies on CdZnTe ternary alloys

Synchrotron radiation x-ray absorption fine-structure and Raman studies on CdZnTe ternary alloys

High-energy X-ray diffraction and topography investigation of CdZnTe

Effects of Surface Processing on the Response of CZT Gamma Detectors: Studies with a Collimated Synchrotron X-Ray Beam

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