Keys to the Enhanced Performance of Mercuric Iodide Radiation Detectors Provided by Diffraction Imaging

1999 ◽  
Vol 590 ◽  
Author(s):  
Bruce Steiner ◽  
Lodewijk van den Berg ◽  
Uri Laor
Keyword(s):  
High Resolution ◽  
Electronic Transport ◽  
Structural Control ◽  
Room Temperature ◽  
Radiation Detectors ◽  
High Energy ◽  
Space Program ◽  
Mercuric Iodide ◽  
High Energy Radiation ◽  
Diffraction Imaging

ABSTRACTHigh resolution monochomatic diffraction imaging is playing a central role in the optimization of novel high energy radiation detectors for superior energy resolution at room temperature. In the early days of the space program, the electronic transport properties of mercuric iodide crystals grown in microgravity provided irrefutable evidence that substantial property improvement was possible. Through diffraction imaging, this superiority has been traced to the absence of inclusions. At the same time, other types of irregularity have been shown to be surprisingly less influential. As a result of the knowledge gained from these observations, the uniformity of terrestrial crystals has been modified, and their electronic properties have been enhanced. Progress toward property optimization through structural control is described.

The Fabrication of Mercuric Iodide Detectors for Use in Wavelength Dispersive X-Ray Analysers and Backscatter Photon Measurements

1982 ◽  
Vol 16 ◽  
Author(s):  
John H. Howes ◽  
John Watling
Keyword(s):  
Room Temperature ◽  
Gamma Ray ◽  
Surface Passivation ◽  
Electrical Contact ◽  
Scintillation Counter ◽  
Radiation Detectors ◽  
Nuclear Radiation ◽  
Gamma Ray Spectrometry ◽  
Mercuric Iodide ◽  
X Ray

ABSTRACTThis paper describes the fabrication of mercuric iodide nuclear radiation detectors suitable for X and gamma ray spectrometry at room temperature. The active area of the detectors studied are between 0.2 and 1.5cm sq and they are up to 0.5mm thick. The method of producing a stable electrical contact to the crystal using sputtered germanium has been studied. The X-ray resolution of a 1.5cm sq. area detector at 32 keV is 2.3 keV FWHM when operated at room temperature in conjunction with a time variant filter amplifier. A factor which is important in the fabrication of the detector is the surface passivation necessary to achieve a useful detector life.This type of detector has been used on a wavelength dispersive X-ray spectrometer for energy measurements between 10 and 100 keV. The advantages over the scintillation counter, more commonly used, is the improved resolution of the HgI2 detector and its smaller size. The analyser is primarily used for the detection of low levels of heavy metals on particulate filters. The detectors have also been used on an experimental basis for gamma ray backscatter measurements in the medical field.

Process Monitoring for Fabrication of Mercuric Iodide Room Temperature Radiation Detectors

1993 ◽  
Vol 324 ◽  
Author(s):  
J. M. Van Scyoc ◽  
T. E. Schlesinger ◽  
H. Yao ◽  
R. B. James ◽  
M. Natarajan ◽  
...  
Keyword(s):  
Room Temperature ◽  
Radiation Detectors ◽  
Electrical Contacts ◽  
Careful Study ◽  
Mercuric Iodide ◽  
Optical Functions ◽  
Processing Step ◽  
Material Choice ◽  
Temperature Radiation ◽  
Processing Steps

AbstractIn the fabrication of mercuric iodide room temperature radiation detectors, as in any semiconductor process, the quality of the final device can be very sensitive to the details of the processing steps. Each processing step can either reduce the intrinsic defects and those extrinsic defects introduced by earlier steps, or it can introduce new defects. In mercuric iodide these defects can act as trapping and recombination centers, thereby degrading immediate device performance or leading to long-term reliability problems. With careful study and monitoring of each step, the process can be modified to improve the end product. In this work we used several techniques to study processing steps and their effects. Photoluminescence spectroscopy and photoionization revealed defects introduced during processing. One critical step is the formation of electrical contacts, as both the material choice and deposition method have an impact. Four point probe sheet resistance methods were used to characterize the loss of material from the contact as it reacted with or moved into the bulk semiconductor. Ellipsometry was used to characterize the intrinsic optical functions of the material, and to study the effects of surface aging on these functions. Results from this work provide suggestions for the modification and monitoring of the detector fabrication process.

Front Cover: Ultrahigh gain AlGaN/GaN high energy radiation detectors (Phys. Status Solidi A 8/2012)

2012 ◽  
Vol 209 (8) ◽  
Author(s):  
J. D. Howgate ◽  
M. Hofstetter ◽  
S. J. Schoell ◽  
M. Schmid ◽  
S. Schäfer ◽  
...  
Keyword(s):  
Radiation Detectors ◽  
High Energy ◽  
High Energy Radiation ◽  
Front Cover ◽  
Energy Radiation

Investigation of Lead Iodide Crystals for Use as High Energy Solid State Radiation Detectors

1993 ◽  
Vol 302 ◽  
Author(s):  
Dominique C. David ◽  
R. B. James ◽  
H. Feemster ◽  
R. Anderson ◽  
A. J. Antolak ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Solid State ◽  
Gamma Rays ◽  
Room Temperature ◽  
Radiation Detectors ◽  
High Energy ◽  
Device Performance ◽  
Lead Iodide ◽  
State Radiation ◽  
Energy Gamma

ABSTRACTSignificant developments have occurred in the technology of room-temperature PbI2 nuclear sensors which lead to some improvements in the detection of high energy gamma-rays. Discussion of crystal growth, purification, monitoring purification, and detector processing are reviewed as they relate to device performance.

Enhancement of Mercuric Iodide Detector Performance Through Crystal Growth in Microgravity: the Roles of Lattice Order

1997 ◽  
Vol 487 ◽  
Author(s):  
Bruce Steiner ◽  
Lodewijk Van Den Berg ◽  
Uri Laor
Keyword(s):  
Crystal Growth ◽  
Crystal Lattice ◽  
Hole Mobility ◽  
Radiation Detectors ◽  
High Energy ◽  
Structural Features ◽  
Mercuric Iodide ◽  
Detector Performance ◽  
Lattice Order ◽  
Extraneous Material

AbstractThe hole-mobility•carrier-lifetime product of α mercuric iodide high energy radiation detectors has been enhanced through vapor crystal growth in microgravity. This improvement is closely correlated with specific characteristics of the crystal lattice, which have been identified by high resolution synchrotron x-ray diffraction imaging. These structural features and the associated performance are now being approached in terrestrial growth of α mercuric iodide.Gravity may affect the uniformity of this crystal lattice in two distinct ways: 1) directly through deformation that it imposes on the lattice during growth and 2) indirectly through convection, which mixes any extraneous material. Inclusions associated with these processes harden the lattice and facilitate lattice folding. These changes affect the electronic parameters of detectors made from the crystals. As purification procedures are optimized, the incorporation of extraneous material is curtailed, enhancing electronic properties in spite of lattice flexing through loss of precipitation hardening.These studies provide insight into the contribution of various aspects of crystalline order in α-mercuric iodide crystals to property improvement. This knowledge has led to modification of requirements for starting materials, adjustment of physical vapor growth procedures, and change in crystal handling procedures. As a result, the electronic performance of terrestrially grown radiation detectors has been improved, and we provide evidence that further enhancement is still possible.

Defects and Impurities in Mercuric Iodide Processing

1995 ◽  
Vol 378 ◽  
Author(s):  
J. M. Van Scyoc ◽  
R. B. James ◽  
T. E. Schlesinger ◽  
T. S. Gilbert
Keyword(s):  
Room Temperature ◽  
Radiation Detectors ◽  
Mercuric Iodide ◽  
Process Step ◽  
Charged Center ◽  
Recombination Centers ◽  
Temperature Radiation ◽  
Positively Charged ◽  
Impurities And Defects

AbstractIn the fabrication of mercuric iodide (HgI2) room temperature radiation detectors, as in any semiconductor process, the quality of the final device is very sensitive to the impurities and defects present. Each process step can change the effects of existing defects, reduce the number of defects, or introduce new defects. In HgI2 detectors these defects act as trapping and recombination centers, thereby degrading immediate performance and leading to unstable devices. In this work we characterized some of the defects believed to strongly affect detector operation. Specifically, we studied impurities that are known to be present in typical HgI2 materials. Leakage current measurements were used to study the introduction and characteristics of these impurities, as such experiments reveal the mobile nature of these defects. In particular, we found that copper, which acts as a hole trap, introduces a positively charged center that diffuses and drifts readily in typical device environments. These measurements suggest that Cu, and related impurities like silver, may be one of the leading causes of HgI2 detector failures.

Characterization of the vapour grown CdTe crystals for high energy radiation detectors

2006 ◽  
Vol 3 (4) ◽  
pp. 717-721 ◽  
Author(s):  
V. D. Popovych ◽  
I. S. Virt ◽  
D. I. Tsutsura ◽  
Z. F. Tsybrii (Ivasiv) ◽  
F. F. Sizov ◽  
...  
Keyword(s):  
Radiation Detectors ◽  
High Energy ◽  
High Energy Radiation ◽  
Energy Radiation

Ultrahigh gain AlGaN/GaN high energy radiation detectors

2012 ◽  
Vol 209 (8) ◽  
pp. 1562-1567 ◽  
Author(s):  
J. D. Howgate ◽  
M. Hofstetter ◽  
S. J. Schoell ◽  
M. Schmid ◽  
S. Schäfer ◽  
...  
Keyword(s):  
Radiation Detectors ◽  
High Energy ◽  
High Energy Radiation ◽  
Energy Radiation
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