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The results of investigation into cesium hafnium chloride (Cs 2 HfCl 6 ) scintillating crystals as a promising detector to search for rare nuclear processes occurring in Hf isotopes is reported. The light output, quenching factor, and pulse-shape characteristics have been investigated at room temperature. The scintillation response of the crystal induced by α -particles and γ -quanta were studied to determine possibility of particle discrimination. Using the optimal filter method we obtained clear separation between signals with a factor of merit (FOM) = 9.3. This indicates that we are able to fully separate signals originating from α -particles and γ -quanta. Similar fruitful discrimination power was obtained by applying the mean time method (FOM = 7) and charge integration method (FOM = 7.5). The quenching factor for collimated 4 MeV α -particles is found to be 0.36, showing that α -particles generate more than a third of the light compared to γ -quanta at the same energy.

Strontium iodide (SrI 2 ), an important new scintillator crystal having a high light yield and excellent energy resolution, was grown for the first time by the edge-defined film-fed (EFG) growth method. Using high purity starting materials and floating dies made of graphite, fused quartz or AlN, large cylindrical, planar or square cross-section single crystals (12–15 mm across and >7 cm long) were produced at growth rates up to 15 mm/h, significantly faster than the current Bridgman growth technology. Details on the equipment used to grow this deliquescent material and on its growth behavior are given along with some discussion of crystalline quality.

In this article we report the evaluation of thick (up to 10 mm) as-grown Cd0.9Zn0.1Te(CZT):In detectors fabricated from ingots grown by traveling heater method (THM). The crystals were investigated by mapping the electron mobility (μe), (μτ)e and the internal electric field of as-grown CZT samples. The detector performance was also evaluated in co-planar grid geometry. The excellent (μτ)e value and the detector performance of 10 mm thick as-grown detectors is the indication that the THM technique can be employed successfully to fabricate the detectors directly from the as-grown boule at substantially lower cost.

This work focuses on the 3. Resultsanddiscussioncharacterization of 10×10×10 mm 3 THM-grown CdZnTe detector-grade crystals that have been post-growth annealed to remove the secondary phases (SPs). All three detectors showed an average energy resolution of ∼1.63% for a small guarded pixel with 3.5 mm diameter, measured using 137 Cs—662 keV with an average peak-to-Compton ratio of 2.7. The characterization showed vestiges of SPs and micro-twins present in some of the crystals indicating that the SPs prior to annealing were large and had size in the range of 100–500 μm. The various detectable structural features, such as micron twins, strains and sub-micron level of Te inclusions seemed to have little or no influence in the radiation spectrometer performance of the detectors; this is possibly because they are either having low density or electrically inactive.

The concentration, size and spatial distribution of Te inclusions in the bulk of CdMnTe crystals mined from two batches of ingots were studied. An isolated planar layer decorated with Te inclusions was identified in CdMnTe crystals from the second ingot. The internal electric field of a CMT crystal was probed by infrared (IR) imaging employing Pockels electro-optic effect. The effect of an isolated plane of Te inclusions on the internal electric-field distribution within the CdMnTe crystal was studied. Space charge accumulation around the plane of Te inclusions was observed, which was found to be higher when the detector was reverse-biased. The effects of the plane of Te inclusions on the electric-field distribution within the CdMnTe crystal, and the quality of CdMnTe crystals for nuclear detector applications are discussed.

Synthetic Cd1–xZnxTe or “CZT” crystals are highly suitable for γ-spectrometers operating at room temperature. Secondary phases (SP) within CZT, presumed to be Te metal, have detrimental impacts on the charge collection efficiency of fabricated device. Using analytical techniques rather than arbitrary theoretical definitions, we identify two SP morphologies: (i) many void, 20-μm “negative” crystals with 65-nm nanoparticle residues of Si, Cd, Zn, and Te and (ii) 20-μm hexagonal-shaped bodies, which are composites of metallic Te layers with cores of amorphous and polycrystalline CZT material that surround the voids.

Selected possible applications of (Cd, Mn)Te, a classical wide-bandgap semimagnetic semiconductor, will be described. Both the semimagnetic character and the other physical properties of this material give rise to its wide applications. As a semimagnetic semiconductor (Cd, Mn)Te demonstrates “giant Faraday rotation” (of the direction of polarization in a strong static magnetic field) for photons with energy a little below that of the free exciton energy. This effect, which is strongest at low temperatures, is also significant at room temperature. (Cd, Mn)Te-based “Faraday rotators” can be used in optical telecommunications as “optical isolators” between the source of radiation (a strong laser) and the rest of the optical transmission line to avoid having parasitic light reflected back to the laser and disturbing its operation. In (Cd, Mn)Te crystals the Faraday effect is extremely fast. The results of the experiments, showing that the response time of the (Cd, Mn)Te crystals to a pulsed magnetic field is in the range 300–500 fs, will be presented, as well as the possible applications of this super-fast Faraday effect. As a wide-bandgap semiconductor with high stopping power for X- and γ-rays, (Cd, Mn)Te can be applied to the construction of radiation detectors. The required parameters: high resistivity (∼10 10 Ω cm) and a high mobility–lifetime product ( μτ = 3 × 10 −3 cm 2 /V) have already been achieved and the results will be described.

Cadmium zinc telluride (CZT) is one of the most promising materials for large-volume gamma-ray spectrometers and imaging arrays. However, because of deficiencies in the high quality material, high-resolution CZT spectrometers are still limited to relatively small dimensions (

The effects of polishing on the electron mobility-lifetime product of a detector-grade Cd/sub 1-x/Zn/sub x/Te (CZT) crystal is reported. The two surfaces of the crystal were deposited with Au layers and illuminated with subband light. A direct current (dc) photocurrent technique was used to measure the electron mobility-lifetime product as a function of the illuminating power. The measured dependence of the electron mobility-lifetime product on the photogenerated electron concentration was highly affected by the condition of the irradiated surface. This discovery has important implications for processing of CZT surfaces for radiation detector applications.

The need for large, room-temperature gamma-ray spectrometers to be fabricated from a single crystalline section of a cadmium zinc telluride (CZT) boule was recently met by progress in crystal growth of high-resistivity material. The characterization of such large crystals provides us with an opportunity to better understand the detector physics and apply characterization techniques, which were difficult to implement and analyze on smaller crystals. In this study, metal-semiconductor-metal, planar-CZT detectors were fabricated from large (approximately 9 × 9 × 6 mm3), CZT single crystals. We have investigated the relationship between the results of the electric-field mapping via Pockels effect, photoconductivity data, and detector performance. Changes in the surface recombination and device characteristics showing departure from symmetry are caused and revealed by variations in the surface preparation.

Chalcopyrite crystals of 6LiInSe2 have recently been shown to respond to gamma and thermal neutron radiation. Thus far, large crystals have been prepared although the charge collection efficiency has not been sufficient for high energy resolution. In an effort to improve energy resolution needed for gamma spectroscopy as well as pulse shape discrimination for mixed gamma neutron fluxes, the precipitate concentration within the 6LiInSe2 crystal have been studied. The precipitate volume greatly affects the energy resolution in the pulse height spectrum. Further, the charge mobility varies greatly with holes being preferentially trapped by these precipitates or some other defect site within the crystal.

Introduction Devant un exantheme febrile du sujet jeune, certains diagnostics doivent etre evoques notamment les causes infectieuses ou une toxidermie. Nous rapportons un cas d’infection bacterienne peu connue responsable d’un exantheme febrile associe a une pharyngite. Observation Un homme de 22 ans etait hospitalise pour une eruption febrile associee a un syndrome grippal et a une odynophagie. A l’examen, on notait un exantheme maculopapuleux rouge vif diffus touchant aussi les extremites. Sur la face interne des cuisses, on notait en sus de l’erytheme un blanchiment au centre des lesions. Il existait une pharyngite et une polyadenopathie cervicale. Le patient rapportait la prise d’ibuprofene et de Rhinadvil ® trois jours avant le debut de l’atteinte cutanee. Le bilan biologique montrait une polynucleose neutrophile a 15 000 elements/mm 3 et une CRP a 172 mg/L sans autre anomalie. Les hemocultures etaient steriles. Les serologies pour la rougeole, le VIH, les hepatites B et C, l’EBV, le parvovirus B19, le CMV et la syphilis etaient negatives, de meme que la recherche de Mycoplasma pneumoniae dans la gorge. Une biopsie cutanee montrait un infiltrat inflammatoire dermique comportant des lymphocytes et des polynucleaires neutrophiles ainsi qu’une petite pustule intra-epidermique superficielle. Une culture et une technique de MALDI TOF d’un prelevement de gorge etait realisee et identifiait Arcanobacterium haemolyticum . L’evolution etait favorable en une semaine sous erythromycine orale. Discussion Arcanobacterium haemolyticum est un bacille gram positif pouvant etre a l’origine d’une pharyngite associee a un exantheme, essentiellement chez des sujets jeunes. La presentation de cet exantheme est particuliere par sa localisation acrale et un caractere considere parfois comme pseudo-urticarien, en fait ici maculopapuleux fixe. Le blanchiment central des lesions, deja decrit dans la litterature au cours de cette affection, pourrait permettre de le differencier des autres causes d’exantheme. A notre connaissance, la presence d’une pustule intra-epidermique, qui aurait pu faire discuter une pustulose exanthematique et egarer le diagnostic, n’a jamais ete rapportee. Des cas d’infections viscerales severes profondes et de septicemies associees ont ete rapportes. Cette entite est probablement sous diagnostiquee car seuls des examens bacteriologiques sur frottis de gorge permettent de mettre A. haemolyticum en evidence. Le traitement de premiere intention repose sur les macrolides, en particulier l’erythromycine orale. Conclusion Nous souhaitons attirer l’attention sur une cause non rare mais meconnue d’exantheme febrile du sujet jeune. L’infection a A. haemolyticum fait partie des diagnostics differentiels a evoquer devant un exantheme du sujet jeune. Le germe peut etre identifie sur un prelevement de gorge, geste qui devrait etre realise largement devant un tel tableau clinique.

Cadmium Zinc Telluride (CZT) is the detector material of choice for the detection of X-rays in the 10 keV-1MeV energy band with excellent spatial and energy resolutions and without cryogenic cooling. In this contribution, we report on recent results of the CZT detector development program and several astrophysical experiments which make use of CZT detectors. In the first part of the paper, we discuss the performance of pixel and cross-strip CZT detectors read out with an ASIC developed at the Brookhaven National Laboratory. Our pixel detectors achieve some of the best energy resolutions reported in the literature. Cross-strip detectors are found to give an inferior performance and we investigate the reason for this performance difference. We also present results from a precision measurement of the effect of a steering grid on multi-pixel events obtained with a 200 micrometer collimator. In the second part of the paper, we describe the design and performance of the hard X-ray polarimeter X-Calibur. The polarimeter uses a 14 cm long scintillator scatterer, surrounded by an assembly of 32 2-5 mm thick CZT detectors. We discuss the sensitivity of the polarimeter to measure the linear polarization of 10 keV-80 keV X-rays on short and long balloon flights and results from testing the polarimeter in the laboratory.

CdZnTe, commonly known as CZT is the material of paramount importance for hard X-ray and gamma ray spectroscopy and imaging applications at room temperature. Over the years, the quality of CZT crystals and its charge transport properties has improved significantly making it an attractive detector material especially for homeland security applications. The applications for homeland security demand large and thick detectors to provide a sufficient stopping power for fast detection of high energy gamma photons. In this present report we have grown two inch diameter CZT by Traveling heater method (THM) technique. The as-grown crystals were characterized through photoluminescence (PL) mapping for composition uniformity, growth interface study, Te precipitations/inclusions studies. In order to evaluate our as-grown samples, charge transport characteristics have been studied for thick samples up to ~16mm thick. It has been demonstrated that by controlling the growth interface, visualization of large and thick (~16mm thick) detectors with fairly good response is possible from as-grown CZT detectors grown by THM technique.

Synthetic CdZnTe or “CZT” crystals are highly suitable for γ-spectrometers operating at the room temperature. Secondary phases (SP) in CZT are known to inhibit detector performance, particularly when they are present in large numbers or dimensions. These SP may exist as voids or composites of non-cubic phase metallic Te layers with bodies of polycrystalline and amorphous CZT material and voids. Defects associated with crystal twining may also influence detector performance in CZT. Using transmission electron microscopy, we identify two types of defects that are on the nano scale. The first defect consists of 40 nm diameter metallic Pd/Te bodies on the grain boundaries of Te-rich composites. Although the nano-Pd/Te bodies around these composites may be unique to the growth source of this CZT material, noble metal impurities like these may contribute to SP formation in CZT. The second defect type consists of atom-scale grain boundary dislocations. Specifically, these involve inclined “finite-sized” planar defects or interfaces between layers of atoms that are associated with twins. Finite-sized twins may be responsible for the subtle but observable striations that can be seen with optical birefringence imaging and synchrotron X-ray topographic imaging.

The Czochralski pulling process is the most valuable and cost efficient method for producing large oriented single crystals of the group IV and III-V semiconductors. However, there have been only a small number of reported attempts to use the Czochralski process for growing the wide bandgap compound semiconductors, needed for the room temperature operated gamma-ray detectors. The main difficulty is in the low chemical stability and high vapor pressure of the group II, V and VI elements, leading to off-stoichiometric composition, and various related defects. Among the heavy metal halides, indium iodide and indium bromide present an interesting exception. InI has a high molecular disassociation energy and a low vapor pressure, allowing for Czochralski pulling. We will describe the procedures used and the results obtained by Czochralski growth and characterization of indium iodide and the related ternary compounds that appear to be quite encouraging.

We are developing new scintillator materials that offer potential for high resolution gamma ray spectroscopy at low cost. Single crystal SrI 2 (Eu) offers ∼3% resolution at 662 keV, in sizes of ∼1 in3. We have developed ceramics processing technology allowing us to achieve cubic inch scale transparent ceramic scintillators offering gamma spectroscopy performance superior to NaI(Tl). Our bismuth-loaded plastic scintillator demonstrates energy resolution of ∼8% at 662 keV, for samples of ∼0.5 cm3.

Cadmium Zinc Telluride (CZT) continues to progress in quality and cost as a material for the detection of hard X-ray and gamma-ray photons with excellent spatial and energy resolutions. We are developing large-volume (0.5×3.9×3.9 cm 3 ) cross-strip CZT detectors with the objective to combine the excellent performance achieved so far only with pixelated CZT detectors with a reduced number of readout channels. In this contribution, we discuss the spectroscopic performance of large volume CZT detectors from the company Orbotech when contacted as pixelated detectors. Subsequently, we present results obtained when the same substrates where contacted with cross-strip contacts. Finally, we use the results from a simulation study to discuss the optimization of the design of the strip contacts and the readout electronics.

We report on the continued development and testing of unique types of Cadmium Zinc Telluride (CZT) detectors.Using large volume (10 × 20 × 20 mm 3 ) CZT crystals, we contact variou s dual anodeŽ detector designs. Weincorporate a segmented cathode with “ve regions so that the charge on all seven contacts can be used todetermine the energy and the 3-D interaction location of detected X-ray and gamma-ray photons. We describethe status of the detector development program, emphasize strengths and weaknesses of the dierent contactcon“gurations, and discuss possible applications of Dual Anode Detectors in radiation detection applications.Keywords: CZT, X-ray Detector , Contact Geometry 1. INTRODUCTION The high average atomic number ( 50) and room temperature operation of Cadmium Zinc Telluride (CZT)detectors make them desirable for Homeland Security a pplications where high eciency of detecting nuclearartifacts is required, such as a stand o detector at a border crossing. We currently are working to developlarge-volume CZT detectors with few re adout channels by exploring novel contact designs. Such designs presentcertain advantages while avoiding the complications, limitations, and requirements of using the standard contactpatterns.The most common CZT detector designs in use today employ either pixel contacts or a coplanar grid (CPG)for the anode.

In an effort to optimize the spectroscopic performance of large volume Cadmium Zinc Telluride (CZT) radiation detectors grown by the Traveling Heater Method (THM), especially for higher energy gamma detection applications, bulk material and pixellated detector performance of THM CZT crystals at 15mm-thick and 10mm-thick were compared to that at 5mm-thick. We demonstrate that the outstanding performance of monolithic pixellated THM CZT detectors was thickness-scalable. For the same monolithic 20×20 mm2 “Compton Camera” pixellated detector configuration, detector performance can certainly be significantly improved as the thickness of the detector increases from 5mm to 10mm and thicker as demonstrated via both 57Co 122 keV and 137Cs 662 keV spectral responses. Depth of interaction information obtained from 3D depth sensing measurement system, IR microscopy and x-ray topography were used to study the correlation between structural quality and detector performance. Additional material characterizations and detector performances of various sizes and configurations were also presented and discussed.

We report the case of a young smoker woman who developed a severe acrosyndrome of rapid onset, involving both hands except the thumbs. The angiography showed digital arteritis. Antinuclear antibodies were present at high level. Three months later, a large B cell lymphoma was diagnosed. Complete remission was achieved, but the acrosyndrome persisted with only partial improvement. The antinuclear antibodies disappeared. The paraneoplastic nature of the acrosyndrome is discussed.

The detector material Cadmium Zinc Telluride (CZT), known for its high resolution over a broad energy range, is produced mainly by two methods: the Modified High-Pressure Bridgman (MHB) and the High-Pressure Bridgman (HPB) process. This study is based on MHB CZT substrates from the company Orbotech Medical Solutions Ltd. with a detector size of 2.0x2.0x0.5 cm^3, 8x8 pixels and a pitch of 2.46 mm. Former studies have emphasized only on the cathode material showing that high-work-function improve the energy resolution at lower energies. Therfore, we studied the influence of the anode material while keeping the cathode material constant. We used four different materials: Indium, Titanium, Chromium and Gold with work-functions between 4.1 eV and 5.1 eV. The low work-function materials Indium and Titanium achieved the best performance with energy resolutions: 2.0 keV (at 59 keV) and 1.9 keV (at 122 keV) for Titanium; 2.1 keV (at 59 keV) and 2.9 keV (at 122 keV) for Indium. These detectors are very competitive compared with the more expensive ones based on HPB material if one takes the large pixel pitch of 2.46 mm into account. We present a detailed comparison of our detector response with 3-D simulations, from which we determined the mobility-lifetime-products for electrons and holes. Finally, we evaluated the temperature dependency of the detector performance and mobility-lifetime-products, which is important for many applications. With decreasing temperature down to -30C the breakdown voltage increases and the electron mobility-lifetime-product decreases by about 30% over a range from 20C to -30C. This causes the energy resolution to deteriorate, but the concomitantly increasing breakdown voltage makes it possible to increase the applied bias voltage and restore the full performance., Accepted for publication in Astroparticle Physics, 25 pages, 13 figures

The performance of current long-drift-length Cadmium Zinc Telluride (CZT) detectors principally is determined by the material's quality. Hence, the material's limitations must be better understood and potential solutions identified to grow CZT crystals with the required qualities. Our efforts have focused on developing novel techniques and testing methods that will allow us to explore the correlations between the crystal's defects and the detector's properties. Local stoichiometric variations and other local disordering make it very hard to systematically correlate performance and material defects on a macroscopic scale. Therefore, to delineate the factors limiting the energy resolution of CZT detectors, we directed our efforts towards micron-scale material characterization and assessments of the detectors using the National Synchrotron Light Source (NSLS). The NSLS offers us a highly collimated high-intensity X-ray beam that we employed to undertake detector-performance mapping, and to investigate the association between microscopic defects and fluctuations in collected charge. In this paper, we illustrate our techniques and results.

High quality detector grade GaSe and GaTe single crystals have been grown by a modified vertical Bridgman technique using high purity Ga (7N) and in-house zone refined (ZR) precursor materials (Se and Te). A state-of-the-art computer model, MASTRAPP, is used to model heat and mass transfer in the Bridgman growth system and to predict the stress distribution in the as-grown crystals. The model accounts for heat transfer in the multiphase system, convection in the melt, and interface dynamics. The crystals harvested from ingots of 8-10 cm length and 2.5 cm diameter, have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, low temperature photoluminescence (PL), atomic force microscopy (AFM), and optical absorption/transmission measurements. Single element devices up to 1 cm 2 in area have been fabricated from the crystals and tested as radiation detectors by measuring current-voltage (I-V) characteristics and pulse height spectra using 241 Am source. The crystals have shown high promise as nuclear detectors with their high dark resistivity (≥10 9 Ω . cm), good charge transport properties (μτ e ~ 1.4x10 -5 cm 2 /V and μτ h ~ 1.5x10 -5 cm 2 /V), and relatively good energy resolution (~4% energy resolution at 60 keV). Details of numerical modeling and simulation, detector fabrication, and testing using a 241 Am energy source (60 keV) is presented in this paper.

Upon examination we have concluded that none of the alarms indicate the presence of a real threat. A brief history and results from our examination of the NYCT ASP occupancy data sets dated from 2007-05-14 19:11:07 to 2007-06-20 15:46:15 are presented in this letter report. When the ASP data collection campaign at NYCT was completed, rather than being shut down, the Canberra ASP annunciator box was unplugged leaving the data acquisition system running. By the time it was discovered that the ASP was still acquiring data about 15,000 occupancies had been recorded. Among these were about 500 alarms (classified by the ASP analysis system as either Threat Alarms or Suspect Alarms). At your request, these alarms have been investigated. Our conclusion is that none of the alarm data sets indicate the presence of a real threat (within statistics). The data sets (ICD1 and ICD2 files with concurrent JPEG pictures) were delivered to LLNL on a removable hard drive labeled FOUO. The contents of the data disk amounted to 53.39 GB of data requiring over two days for the standard LLNL virus checking software to scan before work could really get started. Our first step was to walk through the directorymore » structure of the disk and create a database of occupancies. For each occupancy, the database was populated with the occupancy date and time, occupancy number, file path to the ICD1 data and the alarm ('No Alarm', 'Suspect Alarm' or 'Threat Alarm') from the ICD2 file along with some other incidental data. In an attempt to get a global understanding of what was going on, we investigated the occupancy information. The occupancy date/time and alarm type were binned into one-hour counts. These data are shown in Figures 1 and 2.« less

Gamma ray spectroscopy for remote sensing applications requires a high sensitivity that can be achieved by a combination of high efficiency and high energy resolution for high energy gamma rays (up to 1 MeV) . While cryogenic germanium detectors or LaBr3:Ce3+ scintillators could in principle satisfy the requirements of many such applications, the search for compact, portable systems that do not require cooling or the use of photomultiplier tubes are still underway. State-of-the-art CdZnTe spectrometers having an energy resolution exceeding 1% have been recently demonstrated, however they have a typical volume that is less than 1 cm3. Large volume (greater than 3 cm3) CdZnTe spectrometers with an energy resolution that is better than 3% are not yet commercially available, although the size of large single crystals that would satisfy the volume requirement can now be grown by various companies with reasonable yield. In this study we have investigated the feasibility of using commercially available large (1-6 cm3) detector grade CdZnTe single crystals to fabricate co-planar gamma spectrometers with a targeted performance that exceeds 3% energy resolution at 662 keV. The fabrication of optimal performance coplanar detectors requires a custom design that might vary for each crystal growth method. Besides the knowledge of the average values of charge carrier concentrations, mobilities and trapping times the physics-based model requires the knowledge of bulk nonuniformities and their effects on local variations in the electric field and electron mobility-trapping-time product. All crystals investigated had tellurium, as second phase. A new type of material inhomogeneity, and its influence on detector's performance, became apparent only in large volume crystals and will be reported.

The layered III-VI semiconductor Gallium Telluride has potential for room temperature gamma ray spectroscopy applications due to its band gap of 1.67 eV, and average atomic number of 45 : 31 (Ga) and 52 (Te). The physical properties of GaTe are highly anisotropic due to covalent bonding within the layer and van der Waals bonding between layers. This work reports the results of surface and bulk processing, surface characterization, and electrical characterization of diodes formed on both the laminar and non-laminar GaTe surfaces. Alpha detection measurements were also performed.

Cadmium Zinc Telluride (CZT) detectors are having a major impact on the field of hard X-ray astronomy. Without the need for cryogenic cooling they achieve good spatial and energy resolutions over the broad energy range from 10 keV to 600 keV. In this paper, we briefly review the historical development of detectors used in X-ray astronomy. Subsequently, we present an evaluation of CZT detectors from the company Imarad. The standard 2x2x0.5 cm detectors, contacted with 8x8 In pixels and an In cathode, exhibit FWHM energy resolutions of 7 keV at 59 keV, and 10 keV at 662 keV. A direct measurement of the 662 keV photopeak efficiency gives 67%. We have started a detailed study of the performance of Imarad detectors depending on surface preparation, contact materials, contact deposition, post-deposition detector annealing, and detector passivation techniques. We present first results from contacting detectors with Cr, Ag, Au, and Pt., Invited Contribution to the 49th International Symposium on Optical Science and Technology (SPIE), August 2004, Denver, CO, SPIE, 49, 5540, 13.01. (2004)

Recent progress has been made in the development of the Modified Vertical Bridgman (MVB) technique for the growths of 3-inch diameter CZT crystals for fabrication of x-ray and gamma-ray detectors to operate at room temperature. 40% and 80% of the ingots have the single crystal volumes over 300cm 3 and 100 cm 3 per ingot respectively. Defects (such as Cd-vacancies, Indium dopants and purity) in CZT have been systematically studied. Detectors fabricated from these CZT ingots showed sharp energy resolution and good uniformity.

Single crystals of semiconductor-grade lithium indium selenide (LiInSe2) were grown using the vertical Bridgman method. The orthorhombic structure of the materials was verified using powder x-ray diffraction. The room temperature band gap of the crystal was found to be 2.85 eV using optical absorption measurements. Resistivity of LiInSe2, obtained using current-voltage measurements, has semiconducting nature (decreases with increasing temperature) and is in order of 1010 Ω·cm. Photoconductivity measurement showed the photocurrent peak at 445 nm. Nuclear radiation devices were fabricated, and alpha particle detection was observed, suggesting that this material could be a candidate for neutron detection applications.

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 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.