Characterization of heterogeneities in detector-grade CdZnTe crystals

Duff, Martine C.; Hunter, Douglas B.; Bürger, A.; Groza, Michael; Buliga, Vladimir; Bradley, J. P.; Graham, G.; Dai, Z. R.; Teslich, Nick E.; Black, David R.; Lanzirotti, Antonio

doi:10.1557/jmr.2009.0165

Cited by 25 publications

(23 citation statements)

References 22 publications

(33 reference statements)

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“…1,6,7,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] In some cases, damage caused by characterization methods can have deleterious effects on the crystal performance. The availability of non-destructive analysis techniques is essential to validate a crystal's quality and its ability to be used for either qualitative or quantitative gamma-ray or Xray detection.…”

Section: Introductionmentioning

confidence: 99%

AFM Characterization of Raman Laser-Induced Damage on CdZnTe Crystal Surfaces

Teague

Hawkins

Duff

et al. 2009

Journal of Elec Materi

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IntroductionHigh quality CdZnTe (or CZT) crystals have the potential for use in room temperature gamma-ray and X-ray spectrometers. 1, 2 Over the last decade, the methods for growing high quality CZT have improved the quality of the produced crystals however there are material features that can influence the performance of these materials as radiation detectors. The presence of structural heterogeneities within the crystals, such as twinning, pipes, grain boundaries (polycrystallinity), and secondary phases (SPs) [3][4][5][6][7][8][9][10][11] can have an impact on the detector performance. There is considerable need for reliable and reproducible characterization methods for the measurement of crystal quality. With improvements in material characterization and synthesis, these crystals may become suitable for widespread use in gamma radiation detection.Characterization techniques currently utilized to test for quality and/or to predict performance of the crystal as a gamma-ray detector include infrared (IR) transmission imaging, synchrotron X-ray topography, photoluminescence spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Raman spectroscopy. 1,6,7,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] In some cases, damage caused by characterization methods can have deleterious effects on the crystal performance. The availability of non-destructive analysis techniques is essential to validate a crystal's quality and its ability to be used for either qualitative or quantitative gamma-ray or Xray detection. The work presented herein discusses the damage that occurs during characterization of the CZT surface by a laser during Raman spectroscopy, even at minimal laser powers.Previous Raman studies have shown that the localized annealing from tightly focused, low powered lasers results in areas of higher Te concentration on the CZT surface. 16 This type of laser damage on the surface resulted in decreased detector performance which was most likely due to increased leakage current caused by areas of higher Te concentration. In this study, AFM was used to characterize the extent of damage to the CZT crystal surface following exposure to a Raman laser. AFM data reveal localized surface damage and increased conductivity in the areas exposed to the Raman laser beam. Materials and MethodsTwo different CZT crystals (CZT3-7-4 and 3-7-8) were used in this study and were obtained from Yinnel Tech (South Bend, IN). They were grown by the modified vertical Bridgman (MVB) method 27 and are composed of ~ 10% Zn content (Cd 1-x Zn x Te, with x=0.1).Both faces of the crystal were finely polished with a series of alumina grit sizes; the finest of which was 0.05 µm.CZT3-7-4 was identified as a moderate performer for gamma-ray spectrometry using an 241 Am source (Figure 1). Both the Cd-terminating face and the Te-terminating face of this crystal were exposed to an Argon ion laser (514.5 nm) in a Raman microscope system. Using the Raman laser, a series of highly damaged fiducial marks (~20 ...

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Section: Introductionmentioning

confidence: 99%

AFM Characterization of Raman Laser-Induced Damage on CdZnTe Crystal Surfaces

Teague

Hawkins

Duff

et al. 2009

Journal of Elec Materi

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“…The projection of this kind of polyhedron looks like a well-defined hexagon when viewed along the 1 1 1 direction. In view of the {1 1 1} planes provide the minimum free energy interfaces between the CZT and the liquid Te inclusions [20], it is possible that there is a higher formation potential for {1 1 1} than for other plane families. Thus, the {1 1 0} and {1 0 0} planes gradually submerged during the extended in situ annealing and cooling processes.…”

Section: Czt Grown Under Te-rich Conditionmentioning

confidence: 99%

“…Since the thermal expansion coefficient of Te is considerably higher than that of CZT, a strong stress results from contraction on cooling down to room temperature, which damages the lattice around the inclusion. Thus, the inclusions are always accompanied with cracks and holes [20][21][22].…”

Section: Czt Grown Under Te-rich Conditionmentioning

confidence: 99%

Morphology evolution of micron-scale secondary phases in CdZnTe crystals grown by vertical Bridgman method

Ye¹,

Wang²,

Wang³

et al. 2011

Journal of Alloys and Compounds

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“…[1][2][3][4] Several factors can affect the charge transport and collection properties of these materials including the presence of defects and heterogeneities such as secondary phases (SPs). [5] Further study will help to delineate the contributions of these defects on the intrinsic electrical properties of CZT. A thorough understanding of the specific relationships between the structural, electronic and optical properties of CZT can help guide future material and application developments.…”

Section: Introductionmentioning

confidence: 99%

Photo-induced currents in CdZnTe crystals as a function of illumination wavelength

Teague

Washington

Duff

et al. 2012

J. Phys. D: Appl. Phys.

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We report variations in the currents of CdZnTe semiconductor crystals during exposure to a series of light emitting diodes of various wavelengths ranging from 470 nm to 950 nm. The changes in the steady-state current of one CdZnTe crystal with and without illumination along with the time dependence of the illumination effects are discussed. Analysis of the de-trapping and transient bulk currents during and after optical excitation yield insight into the behaviour of charge traps within the crystal. Similar behaviour is observed for illumination of a second CdZnTe crystal suggesting that the overall illumination effects are not crystal dependent.

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Characterization of heterogeneities in detector-grade CdZnTe crystals

Cited by 25 publications

References 22 publications

AFM Characterization of Raman Laser-Induced Damage on CdZnTe Crystal Surfaces

AFM Characterization of Raman Laser-Induced Damage on CdZnTe Crystal Surfaces

Morphology evolution of micron-scale secondary phases in CdZnTe crystals grown by vertical Bridgman method

Photo-induced currents in CdZnTe crystals as a function of illumination wavelength

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