Modeling of CZT Response to Gamma Photons Using MCNP and Garfield

2015 ◽  
Vol 1792 ◽  
Author(s):  
Jonathan Lassiter ◽  
Randy Robinson ◽  
Latressa Williams ◽  
Stephen Babalola ◽  
Claudiu Muntele
Keyword(s):  
Energy Deposition ◽  
Electrical Contact ◽  
Charge Trapping ◽  
Radiation Detectors ◽  
Electrical Contacts ◽  
Sensitive Volume ◽  
Commercial Development ◽  
Ir Microscopy ◽  
Field Distortion ◽  
Defective Crystal

ABSTRACTCZT is a semiconductor material that promises to be a good candidate for uncooled gamma radiation detectors. However, to date, technological difficulties in production of large size defect-free CZT crystals are yet to be overcome. The most common problem is accumulation of tellurium precipitates as microscopic inclusions. These inclusions influence the charge collection through charge trapping and electric field distortion. The common work-around solutions are to fabricate pixelated detectors by either grouping together many small volume CZT crystals to act as individual detectors, or to deposit a pixelated grid of electrical contacts on a larger, but defective, crystal, and selectively collect charge. These solutions are satisfactory in an R&D environment, but are unsuitable for mass production and commercial development. Our modeling effort is aimed at quantifying the various contributions of tellurium inclusions in CZT crystals to the charge generation, transport, and collection, as a function of inclusions size, position, and concentration. We model the energy deposition of gamma photons in the sensitive volume of the detector using LANL’s MCNP code. The electron-hole pairs produced at the energy deposition sites are then transported through the defective crystal and collected as integral charge at the electrical contact sites using CERN’s Garfield software package. The size and position distribution of tellurium inclusions is modeled by sampling experimentally measured distributions of such inclusions on a variety of commercially-grown CZT crystals using IR microscopy and image processing software packages.

Electrical contact performance of various electro-deposited graphene reinforced silver-based nanocomposites

2020 ◽  
Vol 62 (4) ◽  
pp. 401-407
Author(s):  
Ramazan Karslioglu ◽  
Lujain Al-Falahi
Keyword(s):  
Pulse Current ◽  
Electrical Contact ◽  
Reverse Current ◽  
Electrical Contacts ◽  
Test Device ◽  
Arc Erosion ◽  
Contact Test ◽  
Grain Sizes ◽  
Contact Erosion ◽  
Pulse Reverse

Abstract Silver and silver(Ag)-graphene(Gr) nanocomposite coatings were prepared via direct current, pulse current and pulse reverse current on copper electrical contacts for evaluating electrical contact performance. The effects of the addition of Gr and current types on microstructure, crystallographic orientation, mechanical properties and electrical contact performance were investigataed via a scanning electron microscope, an X-Ray diffractometer, microhardness test device and an electrical contact test device, respectively. The addition of Gr changed the Ag surface morphology and decreased grain sizes. Moreover, the addition of Gr significantly improved arc erosion resistivity and decreased the average working temperature during the contact test. In addition, pulse current and pulse reverse current provided a significant improvement in microhardness and electrical contact erosion resistance owing to increased embedded graphene amounts in silver layers.

GaN Radiation Detection Research Based on Monte Carlo Method

2014 ◽  
Vol 668-669 ◽  
pp. 1011-1014
Author(s):  
Yang Liu ◽  
Guo Zheng Zhu ◽  
Zhen Ni Xing
Keyword(s):  
Monte Carlo ◽  
Energy Deposition ◽  
Detection Efficiency ◽  
Hadron Collider ◽  
Radiation Detection ◽  
Radiation Energy ◽  
Radiation Detectors ◽  
Detection Mechanism ◽  
Radiation Beam ◽  
The Impact

Gallium nitride (GaN) is the third generation of semiconductor material; it has a large band gap, high thermal conductivity, low dielectric constant, high drift speed, etc. Radiation detectors based on GaN material have small volume, high radiation resistance, and fast response, can be used to replace the existing Large Hadron Collider vertex detector and track detector. Energy deposition characteristic of GaN detectors to radiation beam is an important factor for detection efficiency, and there are many factors that affect the energy deposition characteristics of the detector, like the detection mechanism, the impact of material properties, the type of incident ray, radiation energy, and many other factors. This paper studies the physical properties of GaN detector by calculation based on Monte Carlo simulation. Energy deposition characteristics are discussed respectively for incident γ-ray with different energy, in the front-end and back-end add PTFE material. The results of our study present the theoretical properties of GaN radiation detectors.

Evaluation of Electrical Contact Material Stability on Mercuric Iodide

1993 ◽  
Vol 302 ◽  
Author(s):  
A. Y. Cheng
Keyword(s):  
Free Energy ◽  
Room Temperature ◽  
Electrical Contact ◽  
Radiation Detection ◽  
Electrical Contacts ◽  
Contact Material ◽  
Mercuric Iodide ◽  
Energy Data ◽  
Contact Materials ◽  
Temperature Radiation

ABSTRACTMercuric iodide detectors are leading candidates for room-temperature radiation detection applications. The inherently reactive nature of mercuric iodide limits the number of materials suitable for fabrication of electrical contacts. The theoretical stabilities of elemental contact materials on mercuric iodide were evaluated at 25°C. Additionally, the stabilities of transparent conductive compounds, for photodetector applications, were studied. Calculations were based on Gibbs free energy data, estimates and a series of hypothesized reactions with mercuric iodide. Leading candidate materials were identified and compared to experimental results.

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.

Electrical Contacts and Conductivity of MoS2 Layer Structures

1971 ◽  
Vol 49 (20) ◽  
pp. 2565-2571 ◽  
Author(s):  
A. Souder ◽  
D. E. Brodie
Keyword(s):  
Low Temperatures ◽  
Electrical Contact ◽  
Electrical Contacts ◽  
Experimental Results ◽  
Published Data ◽  
Anisotropic Layer ◽  
Layer Structures ◽  
Self Consistent ◽  
Mos2 Layer ◽  
Meaningful Data

The difficulty of making electrical contact to, and obtaining meaningful data from, strongly anisotropic layer structures is discussed and clarified for MoS2. An analysis of this anisotropy is presented and used to explain experimental results obtained from natural crystals of molybdenite.It is shown that annealed contacts on MoS2 make good electrical contact to the crystal by diffusing the contacting material parallel to the c axis and hence making contact to all of the layers. Just below room temperatures, activation energies [Formula: see text] parallel and [Formula: see text] perpendicular to the c axis are 0.04 to 0.08 eV but [Formula: see text] increases to between 0.08 and 0.12 eV below approximately 200 K, with [Formula: see text] at the low temperatures between 2 and 1.5 from sample to sample.The analysis is used to show that the published data for thick and thin crystals of MoTe2 can be made self-consistent.

scholarly journals High-Purity Germanium Crystal Growing

1982 ◽  
Vol 16 ◽  
Author(s):  
W. L. Hansen ◽  
E.E. Haller
Keyword(s):  
High Purity ◽  
Charge Trapping ◽  
Solid Material ◽  
Radiation Detectors ◽  
Nuclear Radiation ◽  
Active Centers ◽  
Defect Complexes ◽  
Regular Production ◽  
And Control ◽  
Nuclear Radiation Detectors

ABSTRACTThe germanium crystals used for the fabrication of nuclear radiation detectors are required to have a purity and crystalline perfection which is unsurpassed by any other solid material. These crystals should not have a net electrically active impurity concentration greater than 10l0 cm−3 and be essentially free of charge trapping defects.Such perfect crystals of germanium can be grown only because of the highly favorable chemical and physical properties of this element. However, ten years of laboratory scale and commercial experience has still not made the production of such crystals routine. The origin and control of many impurities and electrically active defect complexes is now fairly well understood but regular production is often interrupted for long periods due to the difficulty of achieving the required high purity or to charge trapping in detectors made from crystals seemingly grown under the required conditions.The compromises involved in the selection of zone refining and crystal grower parts and ambients is discussed and the difficulty in controlling the purity of key elements in the process is emphasized. The consequences of growing in a hydrogen ambient are discussed in detail and it is shown how complexes of neutral defects produce electrically active centers.

Influence of Surface Roughness on Friction and Contact Resistance in Sliding Electrical Contacts

2007 ◽  
Author(s):  
Dinesh G. Bansal ◽  
Jeffrey L. Streator
Keyword(s):  
Surface Roughness ◽  
Contact Resistance ◽  
Coefficient Of Friction ◽  
Electrical Contact ◽  
Electrical Current ◽  
Electrical Contacts ◽  
Sliding Electrical Contacts ◽  
The Coefficient Of Friction ◽  
Current Densities

An experiment is conducted to investigate the role of surface roughness on the coefficient of friction and contact resistance of sliding electrical contacts. A hemispherical pin is sliding along both smooth and rough 2-meter rail surface. Tests are performed at both low and moderate sliding speed and for a range of electrical current densities, ranging from 0 to about 12 GA/m2. It was found that surface roughness had a significant influence on the coefficient of friction, with the smoother surfaces exhibiting higher coefficients of friction. Contact resistance, on the other hand, did not show as strong an effect of surface roughness, except for a few parameter combinations. At the higher current densities studied (>10 GA/m2), it was found that the contact resistance values tended to be on the order of 1 mΩ, independent of load, speed and roughness. This convergence may be due to presence of liquid metal film at the interface, which established ideal electrical contact.

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