Preparation and sensitization of tin telluride infrared detectors

The compound tin telluride was prepared with the constituent elements (Sn and Te) by using the standard fusing technique. From x-ray studies the compound was identified as tin telluride. The detectors in the form of thin films were prepared by vacuum evaporation. Conductivity and photoconductivity measurements of the detectors were carried out in the temperature range of 130 to 300 K. These detectors were sensitized by baking them in air at a fixed temperature (413 K) for a fixed time (1800 sec). Resistivity measurements of the detectors with consecutive bakings were also carried out. The photosensitivity of the detectors increases as it is baked reaching an optimum value after which the sensitivity decreases whereas the resistivity of the detectors increases continuously with baking. It is observed that photosensitivity of the detectors increases with decrease of temperature. The increase of sensitivity with baking has been explained on the basis of modulation of barrier due to the development of photovoltage at SnTe and its oxide heterojunctions.     

Multi-layer boron thin-film detectors for neutrons

Intrinsic efficiencies of multi-layer boron-10 thin-film detectors were studied theoretically and experimentally. For multi-layer schemes based on an optimized single-layer film thickness, the practical efficiency is limited to about 42% for thermal neutrons. This is about half the efficiency of a moderated ³He detectors in commercial use for portal monitoring. The efficiency limitation is due to charged particle loss in the boron layers and substrates. The same loss mechanism will prevent all substrate-based boron detectors from ever reaching the intrinsic efficiencies of high-pressure ³He tubes, independent of substrate geometry and material composition. Experimental data also indicate that the multi-layer detector configuration can have an efficiency approaching the theoretical limit. Excellent n/γ discrimination has also been achieved using an ionization chamber.     

新型近红外光电探测材料碲铟汞的研究

研究了一种新型近红外光电探测材料碲铟汞（MIT）晶体，利用垂直Bridgman法成功生长了MIT单晶，并采用X-ray衍射分析、UV-NIR-IR光谱分析及Hall测试对晶体的形态结构及光电性能进行了检测。结果表明：MIT晶体为缺陷闪锌矿结构，其在中远红外波段透过性能较好（ 〉50％），并且随着波长的增大，透过增强．MIT晶体为n型半导体，室温电阻率为4．79×10^2Ω．cm，载流子迁移率为4．6×10^2cm^2．V^-1．s^-1，载流子浓度为2．83×10^13cm^-3。较低的载流子浓度，有利于降低探测器的噪声及提高探测器的能量分辨率。     

Developing Si(Li) nuclear radiation detectors by pulsed electric field treatment

Fabrication of Si(Li) nuclear radiation detectors using lithium ion drift under the action of a pulsed electric field is considered. Optimum treatment regime parameters are determined, including the pulse amplitude, duration, and repetition rate. Experimental data are presented, which show that the ion drift in a pulsed electric field decreases the semiconductor bulk compensation time by a factor of two to four and significantly increases the efficiency of detectors.

     

Solid state nuclear track detectors

The materials science aspects of the use of both polymeric and inorganic solids as detectors for energetic particles are reviewed. The various models proposed to explain the formation of an etchable track by a penetrating particle are discussed, as is the nature and the geometric consequences of the etching process itself. An account is given of the wide-ranging applications of solid state detectors in science and technology.     

Correction of the characteristics of strongly irradiated SiC-based nuclear radiation detectors by increasing the working temperature

Owing to the wide bandgap of silicon carbide, p-n structures based on this semiconductor are characterized by low densities of the generation current. For this reason, it is possible to increase the working temperature of SiC-based p-n detectors of nuclear radiation so as to control the time of emission of nonequilibrium carriers from defect-related trapping centers. We have studied strongly irradiated p-n detectors (with a content of primarily displaced atoms on the order of 2 × 10¹⁷ cm⁻³), determined the temperatures at which the trapped carriers are emitted during the time of pulse formation by the electronics employed, and evaluated the generation current at these temperatures. It is experimentally established that an increase in the temperature leads to a decrease in the negative role of trapping centers. At a temperature of 250°C, it is possible to avoid the localization of electrons on shallow levels spaced by less than 0.76 eV from the conduction band edge.     

Cadmium telluride thin films doped with indium: a morphological study

CdTe thin films doped with indium were studied by Scanning Electron Microscopy (SEM). Samples were prepared using Corning glass as a substrate by the Close-Space Vapour Transport with Hot Walls (CSVT-HW) technique. All the samples were prepared using 500 ?C (T _subs) and 600 ? C (T _CdTe) as substrate and CdTe source temperatures, respectively. Indium (In) was introduced as a dopant by evaporation during thin-film preparation. The In source temperature was varied from 560 ?C to 730 ?C in order to obtain different In concentrations. The mean grain size as a function of the indium temperature and its relationship to electrical properties are analysed. By making mechanical fractures on the thin films, the lateral growth morphology and conditions of contact with the substrate were studied.     

Improving the radiation resistance of semiconductor detectors of radioactive radiation

The possibility of using semiconductor detectors not containing potential barriers (p-n junctions) to measure the intensity radioactive radiation fluxes causing degradation of the electric parameters of detector material is theoretically substantiated. The assumptions are confirmed by experimental results.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 61–63, January, 1994.     

Lithium-drifted,silicon radiation detectors for harsh radiation environments

A model describing the passivation by Li atoms of acceptors arising from radiation damage in Si detectors has been developed. Our studies indicate that it is possible to produce a protocol that will allow the in situ recovery of Lithium-drifted Si particle detectors under irradiation by high-energy particles. Our model for particle damage recovery is supported by preliminary results obtained on the recovery of old, degraded detectors.     

HPGe detectors for low-temperature nuclear orientation

Using the Low-Temperature Nuclear Orientation (LTNO) technique one can study various interesting properties of atomic nuclei and nuclear decay which can be deduced from the measurements of the angular distributions of charged particles emitted during the decay. However, the use of particle detectors working in conditions of LTNO devices (which are generally not available commercially) is a necessary precondition for the realization of these experiments.

Planar HPGe detectors for detection of charged particles at “liquid helium” temperatures were developed and produced at NPI e . Relatively simple technology using vacuum evaporation and diffusion was employed. The performance of detectors at low temperatures was tested and their characteristics measured in a testing cryostat before using them in real experiments.

The HPGe detectors were extensively used in a whole range of LTNO experiments with various physical objectives — in offline (IKS Leuven) as well as online (CERN-ISOLDE, Louvain-la-Neuve — LISOL) experiments. In frame of the project “Meson-Exchange Enhancement of First-Forbidden Beta Transitions in the Lead Region”, the measurements of angular distribution of emitted β-particles allowed to determine experimentally the “meson-exchange currents” contribution to the β-decay. In the project “Isospin Mixing in NZ nuclei”, the isospin-forbidden β-transitions of the nuclei in region (A=50–100) were studied in order to obtain information on the isospin structure of the nuclear states. A new project looking for the possible presence of the tensor currents contribution to the β-decay is being prepared for the CERN-ISOLDE facility.     

Temperature fields in thermal radiation detectors

Results of analysis of thermal processes in a superconducting thermal radiation detector, formulated as a boundary-value problem of complicated heat transfer in a three-dimensional region of complex geometry, are reported. Variants of the problem for simplification are given; the limitations of these assumptions are pointed out.Khar'kov Aviation Institute. Translated from Inzhenerno-Fizicheskii zhurnal, Vol. 64, No. 2, pp. 228–232, February, 1993.     

Photon absorption coefficient and the Franz-Keldysh shift of cutoff wavelength for mercury cadmium telluride detectors

Based on the calculation of photon absorption coefficient alpha and width W of the depletion region of mercury cadmium telluride detectors, we derived the equation for alpha, W and the effective Franz-Keldysh shift Dlambda(ce). An interpretation of the substantial difference between Dlambda(ce) and the maximum Franz-Keldysh shift Dlambda(cm) of the cutoff wavelength is presented. We also propose a method to increase the Dlambda(ce) of mercury cadmium telluride detectors.     

Correcting nonlinear response of mercury cadmium telluride detectors in open path Fourier transform infrared spectrometry

The effect of a nonlinear response of mercury cadmium telluride (MCT) detectors to photon flux is to cause a large offset and a slow variation in the zero-line of single-beam Fourier transform infrared (FT-IR) spectra, which dramatically reduce the accuracy to which strongly absorbing bands or lines can be measured. We describe a noniterative numerical technique by which the baseline offset can be corrected by adjusting the values of the maximum point in the interferogram (the "centerburst") and the points on either side. The technique relies on the presence of three spectral regions at which the signal is known to be zero. Two of these are found in all spectra, namely, the region below the detector cutoff and the high-wavenumber region just below the Nyquist wavenumber where the interferogram has been electronically filtered. In open path FT-IR measurements there are several regions where atmospheric water vapor and CO2 are totally opaque. We have selected the region around 3750 cm(-1). This algorithm is even shown to work well when the interferogram is clipped, i.e., the value at the centerburst exceeds the dynamic range of the analog-to-digital converter.     

Thin- and thick-film real-time gamma radiation detectors

The cruel reality of today's world forces mankind to be alert and prepared for all kinds of terrorist threats, including exposure to radiation. There is a need for cost-effective alternatives to existing commercially available real-time gamma radiation dosimeters. In this paper, numerous oxides such as NiO, CeO/sub 2/, TeO/sub 2/, In/sub 2/O/sub 3/, SiO, MnO, etc., and their mixtures in different proportions were used as the basis for such a substitute. Thin- and thick-film devices were made in the form of resistors and capacitors, structures with interdigitated electrodes, and pn-junctions. These, in different mixtures, were found to change their sensitivity when exposed to /spl gamma/-rays. In general, thin-film devices were found to be more sensitive to lower doses of radiation than the counterpart thick films. However, it was experimentally demonstrated that it is possible to fabricate a device that would satisfy the requirement of a particular application, such as the sensitivity to /spl gamma/-radiation exposure and working dose regions. Based on the above data, these structures might be regarded as a cost-effective alternative for room-temperature real-time /spl gamma/-radiation dosimetry.