Irradiated Silicon Crystals Research Articles

ТАЛШЫҚТЫ-ОПТИКАЛЫҚ БАЙЛАНЫС ЖОЛДАРЫ НЕГІЗІНДЕ ЭНЕРГИЯ ТАРАТУ ЖҮЙЕСІНІҢ ЗЕРТХАНАЛЫҚ ҮЛГІСІН ӘЗІРЛЕУ ЖӘНЕ ЗЕРТТЕУ

In this article, a laboratory sample of an energy transmission system over a fiber-optic communication line is being developed and investigated, which makes it possible to provide power to autonomous ultra-low-power electronic devices located at a considerable distance from energy sources. The system being developed will make it possible to abandon the use of copper conductors and batteries for autonomous stationary devices, which is associated with certain difficulties from the point of view of technical implementation. The result of this study is a developed laboratory sample that allows measuring the values of current and voltage in the branch of the photodetector. The method of an equivalent generator was used, as well as the well-known laws of a circuit with two dedicated nodes for an active two- pole. When analyzing the literature, scientific achievements and discoveries in the field of research, a proprietary research concept was formulated that differs from foreign analogues. During the experiment, the photodetector was in idle, short-circuit mode and was connected to a high-resistance load. Based on experimental data, volt-ampere characteristics (VAC) were constructed using a radiation source (laser) with a power of 10 and 30 MW. The technical parameters and characteristics of the radiation source and the irradiated silicon crystal are given. The output electrical power is determined using the laws of electrical engineering, including Ohm's law. To process the results obtained, quadratic interpolation of the function, the results of the root-mean-square approximation were used, and regression analysis was also performed. Absolute and relative errors were calculated. The student's coefficient was determined with a confidence interval of 0.95. According to the results of the study, the efficiency of a laboratory sample of an energy transmission system over a fiber-optic communication line was determined.

Power supply via fiber-optical conductor for sensors of mine working monitoring system

The article describes a system of power transmission via fiber-optic cable, which allows the supply of power to sensors and other electronic devices of ultra-low power located in places of mining workings, for which the mandatory requirement is fire safety. The developed system will allow to replace the application of copper conductors. The result of this research is the developed laboratory bench that allows measuring the current and voltage parameters in the photodetector branch. The equivalent generator method has been used, as well as the known circuit laws with two dedicated nodes for an active two-terminal network. When analyzing the literature, the existing scientific achievements, and discoveries in the field of research, an own concept of research has been formed that is different from foreign analogs. During the experiment, the studies have been performed when the photodetector was in the short circuit, idle mode, and connected to a high-resistance load. Based on the results obtained, current-voltage characteristics (CVC) and histograms have been built using a radiation source (laser) with a power of 10 and 30 mW. The parameters and technical characteristics of the irradiated silicon crystal and the radiation source have been given. The obtained electrical power has been determined using the known laws of electrical engineering, including the Ohm law. To process the experimental data, there has been used quadratic interpolation of the function, the results of the root-mean-square approximation, and there has been carried out the regression analysis. Absolute and relative errors have been calculated. The Student coefficient has been determined with a confidence interval of 0.95. Based on the results of the study, the efficiency of the power transmission system has been determined

Channeling efficiency reduction in high dose neutron irradiated silicon crystals for high energy and high intensity beam collimation and extraction

The channeling process in bent silicon crystals are used since '70s to manipulate beams of high energy particles. During the last decade, several studies and experiments carried out by the UA9 Collaboration at CERN demonstrated the possibility to use bent crystals for beam collimation, extraction, focusing and splitting in particle accelerators. These crystals are subject to deterioration due to the interaction of the particles with the crystal lattice, degrading the beam steering performance. For this reason, robustness tests are crucial to estimate their reliability and operational lifetime. A ∼8% of reduction in channeling efficiency on crystals irradiated with 2.5·1021/cm2 thermal neutrons was measured and reported in this manuscript. Extrapolations to possible operational scenarios in high energy accelerators are also discussed.

Formation of Oxygen-Containing Centers in Irradiated Silicon Crystals during Annealing in the Temperature Range of 450–700°С

The processes associated with transformations of oxygen-related radiation-induced defects in Czochralski-grown silicon crystals irradiated with fast electrons or neutrons and subjected to heat-treatment in the temperature range of 450–700°C have been studied by means of IR absorption spectroscopy. It is found that, upon disappearance of the VO3 and VO4 defects, new vacancy-oxygen-related complexes, which give rise to a number of vibrational absorption bands in the wavenumber range of 980–1115 cm–1, are formed. It is argued that these complexes are radiation-induced VOm centers (m ≥ 5), which serve as nucleation centers of enhanced oxygen precipitation in silicon.

Mathematical model of mechanically stimulated changes of irradiated silicon crystals’ surface conductivity

Monocrystals of p-Si were used to study the changes in the electrical conductivity of silicon in the course of the action of a single-acting elastic load and X-radiation. An equation describing the dependence of the surface conductivity of irradiated silicon crystals on the amount of elastic deformation (σ) is proposed. This equation made it possible to quantitatively compare the role of the following three radiation-stimulated mechanisms that determine the surface conductivity of p-Si crystals in the course of elastic deformations: (1) reduction of hole mobility (µp); (2) increase of the value of the positive charge in the SiO2 oxidation layer (determined by the factor β1); (3) generation of point defects, which are stoppers for dislocations (determined by the factor β2). If we substitute in the equation for surface conduction the following expressions for a non-irradiated sample: $$\beta_{1} = {1}0^{{{17}}} m^{{ - {2}}} ;\,\beta_{2} \left( \sigma \right) = {1}0^{{{14} }} m^{{ - {2}}} + \sigma \cdot {3}.{51}0^{{7}} Pa^{{ - {1}}} \cdot m^{{ - {2}}} ;\,\mu_{p} \left( \sigma \right) = 0.0{5} m^{{2}} /\left( {V \cdot s} \right) + \sigma \cdot {1}.{5} \cdot {1}0^{{ - {11}}} m^{{2}} /\left( {Pa \cdot V \cdot s} \right),$$ we can get a theoretical curve that almost coincides with the experimental one. By reducing the mobility of holes by 5%, the coefficient β2 by 39%, and by increasing β1 by 4.34%, the theoretical dependence of conductivity on the mechanical load can be obtained for irradiated specimens.

Optical Properties and the Mechanism of the Formation of V2O2 and V3O2 Vacancy–Oxygen Complexes in Irradiated Silicon Crystals

The processes of the formation and annealing of VnOm (n, m ≥ 2) vacancy–oxygen complexes in Czochralski silicon crystals irradiated with fast electrons and reactor neutrons have been studied by infrared absorption Fourier spectroscopy. A number of arguments are presented in favor of identification of absorption bands at 829.3 and 844.2 cm–1 as being related to local vibrational modes of V2O2 and V3O2 complexes, respectively.

Quasi-Chemical Reactions in Irradiated Silicon Crystals with Regard to Ultrafast Irradiation

This paper reports results from an investigation of the interaction of displaced Si-self atoms (I) and their vacancies (V), with impurities in crystalline silicon (Si), as induced by micro-second pulse duration irradiation with electrons at different energies: 3.5, 14, 25 and 50 MeV and pico-second pulse duration with energy 3.5 MeV. V-V, I-impurity atom and V-impurity atom interactions are analyzed both experimentally and as modeled using computer simulations. A process of divacancy (V2) accumulation in the dose-dependent linear region is investigated. The effect of impurities on recombination of correlated divacancies, and I-atoms that had become displaced from regular lattice points is estimated by computer modeling of an appropriate diffusion-controlled process. It is concluded that the experimental results can be interpreted quantitatively in terms of a strongly anisotropic quasi-one-dimensional diffusion of displaced I-atoms. In addition, a significant difference is found between the effects of pico-second duration electron beam irradiation, which causes the formation of A-centre (V + Oxygen) clusters, while when the beam is applied on a micro-second timescale, divacancies are created instead, although the electrons have the same energy in both cases.

Thermally stable carbon–oxygen complexes in irradiated silicon crystals

The origin of the main defect-impurity complexes induced in silicon crystals with different contents of oxygen and carbon impurity atoms by electron irradiation in the temperature range 30–600°C has been investigated by means of IR absorption spectroscopy. The efficiencies of the formation of various optically active centers as a function of temperature of irradiation are obtained. The radiation-enhanced formation of a complex consisting of a substitutional carbon and oxygen dimer (Tirrad = 450°C) is revealed in carbon-containing Si. After irradiation at Tirrad = 500°C, vacancy–oxygen trimer–carbon centers, which give rise to vibrational absorption bands at 902, 956, and 1025 cm−1, are detected for the first time.

High resolution X-ray diffraction study of proton irradiated silicon crystals

Radiation-induced modification of semiconductors is achieved by controlled introduction of intrinsic structural and impurity defects. Conventionally, introduction of radiation-induced defects is used as an efficient tool for controlling the lifetime of metastable carriers in local areas of silicon based devices and supporting mechanisms of avalanche-like breakdown through radiation-induced defect levels. Desired parameters of damaged layers are typically achieved during post-implantation heat treatment. There are recent applications of proton irradiation in silicon technology. A significant growth of luminescence was observed in proton irradiated silicon and attributed to the formation of special rod-shaped clusters of interstitial type radiation defects.We have studied the transformation of radiation-induced defects forming as a result of proton implantation into n silicon crystals with a resistivity of 100Ωcm using high resolution X-ray diffraction and shown that sequential implantation of 100, 200 and 300keV protons with a fluence of 2.1016cm−2 causes the formation of a 2.4μm thick damaged layer with a greater lattice parameter. The layer forms simultaneously with intrinsic clusters of vacancy and interstitial type radiation-induced defects. Vacuum annealing of the irradiated crystals at 600°C increases the power of the radiation-induced defects of both types and reduces their quantity. Interstitial type defects dominate after annealing at 1100°C. We have assessed the power of the defects at every transformation stage.

Low symmetry configurations of vacancy-oxygen complexes in irradiated silicon

Two new electron paramagnetic resonance (EPR) spectra, labeled KU2 and KU3, emerge as a result of annealing of γ-ray irradiated silicon crystals in the temperature range 360–560 °C. The EPR intensities of KU2 and KU3 increase in the upper range of the annealing temperature where the EPR peaks of the vacancy-oxygen complex (A-center) diminish. The angular dependence study shows that the EPR spectra of KU2 and KU3 resemble that of SL1, the excited triplet (spin S = 1) state of A-centers, but with slightly different g and D-tensors representing lowering in symmetries. Microscopic lattice distortions caused by capturing of extra interstitial oxygen atoms by the A-centers are proposed to be the source of lowering of the symmetries associated with KU2 and KU3.

Study of strain propagation in laser irradiated silicon crystal by time-resolved diffraction of K-α x-ray probe of different photon energies

An experimental study on the time resolved x-ray diffraction from laser shocked silicon crystal, carried out using a 10 TW Ti:sapphire laser system, is presented. The characteristic Kα x-ray line radiation generated by 45 fs laser produced plasmas of two different target materials (iron and copper) is used as the probe, whereas the stretched pulse of sub-nanosecond duration (pump), derived from the same laser, is used to compress the sample. The use of x-ray probe of different photon energies yields information about the strain over a greater crystal depth. The dynamics of the strain propagation is inferred by monitoring the evolution of rocking curve width of the shocked sample at different time delays between the pump and the probe pulse. The shock velocity deduced from these measurements is ∼106 cm/s, consistent with the sound velocity in bulk silicon. The maximum elastic compression observed is 0.4%, indicating a pressure of 0.8 GPa.

Picosecond structural dynamics in photoexcited Si probed by time-resolved x-ray diffraction

Direct observation of structural dynamics of a 300 ps laser irradiated silicon crystal is performed by means of picosecond time-resolved x-ray diffraction. Change in x-ray diffraction profiles corresponds to propagation of a strain pulse inside the sample with sound velocity. The strain profiles are simulated by considering carrier dynamics and thermoelastic treatment and well explain the experiments.

Investigation of a simple and efficient method for silicon neutron transmutation doping process in Tehran research reactor

Neutron transmutation doping of silicon (NTD) is one of the important applications in industrial utilization of research reactors. In this paper, the proposed irradiation system based on using a reflecting environment around the irradiation channel of the NTD facility was designed and simulated for irradiation of silicon in the Tehran research reactor (TRR) by using codes such as MCNP, WIMS and CITATION. This system is very simple and does not require conventional methods, such as continuous movement and use of absorbing materials and windows, for flattening of neutron flux in the radial and longitudinal direction. The influence of type and dimensions of reflectors on the irradiated silicon crystal was investigated and also the optimum conditions were determined for TRR for silicon ingots with diameter up to 5 cm and up to 10 cm.

Metallic cluster beams from a 2.5 MV Van de Graaff accelerator for cluster–solid interaction studies: preliminary results with Aun+ clusters

A liquid metal ion source (LMIS) was installed on the high-voltage terminal of the 2.5 MV single-stage Van de Graaff accelerator of the Institut de Physique Nucleaire de Lyon and was used to deliver intense MeV energy beams of cluster ions. After acceleration, the ions produced from an eutectic Au—Si alloy were mass-selected by means of a magnetic analysis. The beam was mainly composed of the monoatomic ions Au+ and Si+ and of the clustersAu n + , Au n Si+, and Au n Si 2 + (n = 2 − 13). The intensities decreased for increasing n values, but remained remarkably high. For pure gold ions, the maximutn intensity measured at the target site varied from 250 nA, for Au+, down to 20 pA, for Au 9 + . The research program on the study of the specific effects of the impact of energetic clusters on solid surfaces concerns the fundamental interaction processes and the solid modifications induced by high-density energy deposits. Our first experiments with Au n + , clusters led to the following results: Nonlinear dependence on the cluster size of kinetic secondary electron emission from thin carbon foil enhances the damage rate of irradiated silicon crystals as compared to monoatomic Au+ ion effects.

New results from the CERN-SPS beam deflection experiments with bent crystals

Results from five distinct bending experiments performed recently in the H8 beam at CERN are presented. Firstly, deflection of a positive pion beam at 200 GeV/c is compared to the “standard” 450-GeV/c proton beam for a bending angle of 3.1 mrad along the (111) plane in a 50 mm silicon crystal. Second, deflection of negative pions at 200 GeV/c is investigated for the same crystal, for incidence along the (111) plane as well as the 〈110〉 axis. Small deflection effects are seen, but no negative particles are bent through the full bending angle of the crystal. Third, the first results from beam deflection at high energy using a germanium crystal are shown. Slightly higher deflection efficiencies than for silicon are seen for large bending angles, but significantly smaller than expected for such a crystal with higher atomic number. Fourth, deflection efficiencies using a strongly irradiated silicon crystal have been measured for the first time, and a small reduction in efficiency is seen in the irradiated region. Finally, deflection of positive particles using axial alignment of a bent silicon crystal has been investigated at 450 GeV/c. Qualitatively similar behaviour as in previous experiments at 12 GeV/c is seen; the beam splits into several beams corresponding to the different planes, and even weak planes are observed.

Neutron transmutation doped silicon detectors with improved carrier lifetime

High resistivity n-type extrinsic silicon with uniform impurity distributions have been produced from ultra-high pure p-type silicon by using the neuron transmutation doping technique. The neuron irradiated silicon crystal has recovered the minority carrier lifetime from an unmeasurable small value to a value of 1 ms after thermal annealing of only 10 min using an infrared lamp furnace. The characteristics of a detector produced by using the improved neutron transmutation doped silicon crystal is found to be as good as those of the conventional silicon detector.

Effets de l'irradiation par des protons sur les propriétés du silicium

The diffusion enhancement is studied in high-temperature proton- irradiated silicon crystals, revealed by the displacement of an n-p junction. The defects created by irradiation are studied. The whole thickness of the crystal may be perturbed. The perturbation disappears after etching away of the region where the defects are created, 10 mu from the surface (depth of penetration of the protons). (auth)