Analysis of Grain Boundaries, Twin Boundaries and Te Precipitates in Cd<sub>1−x</sub>Zn<sub>x</sub>Te Grown bY High-Pressure Bridgman Method

Heffelfinger, J. R.; Medlin, Douglas L.; James, R. B.

doi:10.1557/proc-487-33

Cited by 17 publications

(12 citation statements)

References 6 publications

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“…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.…”

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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“…Specific sites along the grain boundaries and twin boundaries were seen to act as preferential nucleation sites (i.e. triple junctions of grain boundaries, jogs in the twin boundaries) [117][118][119][120]. Experiments show good correlation between the spatial distribution of Te-particles and existing dislocation networks (chuck's work).…”

Section: Defect Generation During Crystal Growthmentioning

confidence: 99%

Simulating Interface Growth and Defect Generation in CZT – Simulation State of the Art and Known Gaps

Henager¹,

Gao²,

Hu³

et al. 2012

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“…The Te inclusions have an elongated plate or saucer shape within grain boundaries; but even here, they tend to line up with neighboring grains and form sharp boundaries. 21 There is significant evidence that Te inclusions and the surrounding defect field have a strong detrimental effect on electron transport in CdZnTe crystals and on the poor performance of the fabricated detector devices. 22,23 It was also shown that the region of degraded charge transport near Te inclusions extends well beyond the volume of the inclusions themselves.…”

Section: Structural Propertiesmentioning

confidence: 99%

Development of the high-pressure electro-dynamic gradient crystal-growth technology for semi-insulating CdZnTe growth for radiation detector applications

Szeles

Cameron

Soldner

et al. 2004

Journal of Elec Materi

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The high-pressure electro-dynamic gradient (HP-EDG) crystal-growth technology has been recently developed and introduced at eV PRODUCTS to grow large-volume, semi-insulating (SI) CdZnTe single crystals for room-temperature x-ray and gamma-ray detector applications. The new HP growth technology significantly improves the downstream CdZnTe device-fabrication yield compared to earlier versions of the HP crystal-growth technology because of the improved structural and charge-transport properties of the CdZnTe ingots. The new state-of-the-art, HP-EDG crystal-growth systems offer exceptional flexibility and thermal and mechanical stability and allow the growth of high-purity CdZnTe ingots. The flexibility of the multi-zone heater system allows the dynamic control of heat flow to optimize the growth-interface shape during crystallization. This flexibility combined with an advanced control system, improved system diagnostics, and realistic heat-transport modeling provides an excellent platform for continuing process development. Initial results on largediameter (140 mm), SI Cd 1-x Zn x Te (x ϭ 0.1) ingots grown in low temperature gradients with the HP-EDG technique show reduced defect density and complete elimination of ingot cracking. The increased single-crystal yield combined with the improved charge transport allows the fabrication of large-volume, high-sensitivity, high energy-resolution detector devices at increased yield. The CdZnTe ingots grown to date produced large-volume crystals (Ն1 cm 3 ) with electron mobility-lifetime product (µτ e ) in the (3-7) ϫ 10 Ϫ3 cm 2 /V range. The lower-than-desired charge-transport uniformity of the HP-EDG CdZnTe ingots is associated with the high density of Te inclusions formed in the ingots during crystallization. The latest process-development efforts show a reduction in the Te-inclusion density, an increase of the charge-transport uniformity, and improved energy resolution of the large-volume detectors fabricated from these crystals.

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Analysis of Grain Boundaries, Twin Boundaries and Te Precipitates in Cd_1−xZn_xTe Grown bY High-Pressure Bridgman Method

Cited by 17 publications

References 6 publications

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

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

Simulating Interface Growth and Defect Generation in CZT – Simulation State of the Art and Known Gaps

Development of the high-pressure electro-dynamic gradient crystal-growth technology for semi-insulating CdZnTe growth for radiation detector applications

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Analysis of Grain Boundaries, Twin Boundaries and Te Precipitates in Cd1−xZnxTe Grown bY High-Pressure Bridgman Method

Cited by 17 publications

References 6 publications

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

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

Simulating Interface Growth and Defect Generation in CZT – Simulation State of the Art and Known Gaps

Development of the high-pressure electro-dynamic gradient crystal-growth technology for semi-insulating CdZnTe growth for radiation detector applications

Contact Info

Product

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Analysis of Grain Boundaries, Twin Boundaries and Te Precipitates in Cd_1−xZn_xTe Grown bY High-Pressure Bridgman Method