Littérature scientifique sur le sujet « Silicon barrier detectors »

Silicon surface barrier (SSB) detectors have been fabricated with oxygen enriched, high-resistivity, detector grade, n-type FZ silicon. Oxygen enrichment of the wafer was done by high-energy (140 MeV) oxygen ion implantation. Annealing of the irradiated silicon wafer was done to minimize the irradiation-induced defect concentration. Positron annihilation lifetime studies were used to select the annealing temperature. A comparative study was carried out among various SSB detectors made from as-grown, as-irradiated and annealed silicon wafers. Detector made from the annealed wafer worked satisfactorily and its performance was comparable with that of a detector made from as-grown crystal.

The development of new types of high-speed photodetectors and techniques to incorporate these detectors into integrated optical structures are reported in this paper. Schottky-barrier detectors with an interdigital electrode configuration have been fabricated on commercially available silicon-on-sapphire substrates. Response times of <30 ps have been measured for wavelengths from infrared to the ultraviolet. These experimental results agree well with a supporting numerical model of these detectors. Using the same electrode configuration, we have fabricated photoconductive detectors on bulk silicon and germanium-on-gallium arsenide substrates. These have slower response times, on the order of a nanosecond, but demonstrate a good responsivity of approximately 1.5 A∙W−1. Using a modified electrode configuration, we have fabricated an integrated detector array on silicon, combining a glass waveguide channel with each detector element for the efficient delivery of an optical input signal.

Abstract The response function of the recoil nuclei in detectors designed for detection of neutrinos or dark matter particles can be determined only through usage of a neutron source with a known energy spectrum. A possible solution for a compact neutron calibration source is a combination of a 252Cf neutron source and a semiconductor detector that detects fission fragments, and thus records the neutron emission moment. This work is devoted to the degradation study of the operating parameters for silicon semiconductor detectors irradiated by fission fragments of the nuclide of 252 Cf. Two types of Si detectors were under investigations - silicon-lithium Si(Li) p-i-n detectors and silicon surface barrier detectors. As a result of the measurements, the maximum permissible radiation doses for the correct operation of both types of detectors and the relation of the received radiation dose to the spectroscopic characteristics of the detectors were determined.

In 2016, the “E-SiCure” project (standing for “Engineering Silicon Carbide for Border and Port Security”), funded by the NATO Science for Peace and Security Programme was launched. The main objective is to combine theoretical, experimental and applied research towards the development of radiation-hard SiC-based detectors of special nuclear materials (SNM), with the end goal to enhance border and port security barriers. Prototype neutron detectors, configured as 4H-SiC-based Schottky barrier diodes, were developed for the detection of secondary charged particles (tritons, alphas and lithium atoms) which are the result of thermal neutron reactions on 10B and 6LiF layers above the surface of the 4H-SiC diodes. We designed a stand-alone prototype detection system, consisting of a preamplifier, shaping amplifier and a multichannel analyser operated by a laptop computer, for testing of neutron detector prototypes at the Jožef Stefan Institute (JSI) TRIGA reactor using a broad beam of reactor neutrons. The reverse bias for the detector diode and the power to electronic system were provided by a standalone battery-powered voltage source. The detector functionality was established through measurements using an 241Am alpha particle source. Two dedicated experimental campaigns were performed at the JSI TRIGA reactor. The registered pulse height spectra from the detectors, using both 10B and 6LiF neutron converting layers, clearly demonstrated the neutron detection abilities of the SiC detector prototypes. The computed neutron detection sensitivity of the single prototype detectors demonstrates that scaling SiC detectors into larger arrays, of dimensions relevant for border and port radiation detectors, could enable neutron sensitivity levels matching gas-based detector technology.

Abstract Deterioration of the operation parameters of p-type Si surface-barrier detector and Si(Li) p-i-n detector upon irradiation by alpha-particles was investigated. The detectors were irradiated at room temperature up to a total number of the registered α-particles Nα equal to 6 × 109. Prolonged irradiation has resulted in a deterioration of the detectors energy resolution ability and it was found that the increase of α-peaks broadening can be described by a linear function of Nα with a slope Δσ/ΔNα ∼ (1.4–1.8) × 10–9 keV/α for both detectors. Resolution deterioration was associated with the increase of the detectors leakage current, which proceeds linearly with the number of absorbed α-particles with the slope ΔI/ΔNα ∼ (7-17) × 10-17 A/α. The increase of the detectors reverse current was related with appearance of radiation-induced defect level at 0.56 eV above the valence band.

The results of an experimental investigation into a new type of VLWIR detector based on hot electron gas emission and architecture of the detector are presented and discussed. The detectors (further referred to as HEGED) take advantage of the thermionic emission current change effect in a semiconductor diode with a Schottky barrier (SB) as a result of the direct transfer of the absorbed radiation energy to the system of electronic gas in the quasimetallic layer of the barrier. The possibility of detecting radiation having the energy of quantums less than the height of the Schottky diode potential barrier and of obtaining a substantial improvement of a cutoff wavelength to VLWIR of the PtSi/Si detector has been demonstrated. The complementary contribution of two physical mechanisms of emanation detection—“quantum” and hot electrons gas emission—has allowed the creation of a superwideband IR detector using standard silicon technology.

Rare Physics event is playing a crucial role, not only in Fundamental Interaction Physics, but also in Astroparticle Physics and in Cosmology. These signals, if detected, would give an importatnt evidence of new Physics. The CUORE experiment (Cryogenic Underground Observatory for Rare Events) is a proposed tightly packed array of 988 TeO2 bolometers, each being a cube 125 cm3 on a side with a mass of 750 g. The array consists of 19 vertical towers, arranged in a compact cylindrical structure. Each tower will consist of 13 layers of 4 crystals. The design of the detector is optimized for ultralow-background searches. Neutrinoless double-beta decay (ββ0ν) is the main goal of CUORE. What is new is the fact that positive observation of neutrino oscillations gives new motivation for more sensitive searches. Neutrino oscillation experiments can only provide data on the mass differences of the neutrino mass-eigenstates. The absolute scale can only be obtained from direct mass measurements (β-decay end point measurements), or in the case of Majorana neutrinos, more sensitively by neutrinoless double-beta decay observation. ββ0ν is not the only exotic process which can be observed in the CUORE experiment. Other rare events, from cold dark matter, to rare nuclear decays and electron decay can in principle be studied with the CUORE experimental facility. I will discuss the last process in the 6th chapter. The topic which joins the exotic and rare processes discussed is the unwanted radioactive background which is inevitably present in the experimental measurements. CUORICINO, almost a single CUORE tower, was constructed as a smaller scale ex- periment and operated from december 2003 to June 2008. Besides being a sensitive experiment on 130Te double beta decay, CUORICINO is a conclusive test of CUORE. CUORICINO provided important results concerning both the technical performances of the bolometric tower (CUORE will be made of 19 such towers), the background level .In particular, one of the information gained is that the most probable candidates for the continuum background observed in the spectra, are the surface α contaminations of the copper mounting frame. Rare Physics event is playing a crucial role, not only in Fundamental Interaction Physics, but also in Astroparticle Physics and in Cosmology. These signals, if detected, would give an importatnt evidence of new Physics. The CUORE experiment (Cryogenic Underground Observatory for Rare Events) is a proposed tightly packed array of 988 TeO2 bolometers, each being a cube 125 cm3 on a side with a mass of 750 g. The array consists of 19 vertical towers, arranged in a compact cylindrical structure. Each tower will consist of 13 layers of 4 crystals. The design of the detector is optimized for ultralow-background searches. Neutrinoless double-beta decay (ββ0ν) is the main goal of CUORE. What is new is the fact that positive observation of neutrino oscillations gives new motivation for more sensitive searches. Neutrino oscillation experiments can only provide data on the mass differences of the neutrino mass-eigenstates. The absolute scale can only be obtained from direct mass measurements (β-decay end point measurements), or in the case of Majorana neutrinos, more sensitively by neutrinoless double-beta decay observation. ββ0ν is not the only exotic process which can be observed in the CUORE experiment. Other rare events, from cold dark matter, to rare nuclear decays and electron decay can in principle be studied with the CUORE experimental facility. I will discuss the last process in the 6th chapter. The topic which joins the exotic and rare processes discussed is the unwanted radioactive background which is inevitably present in the experimental measurements. CUORICINO, almost a single CUORE tower, was constructed as a smaller scale ex- periment and operated from december 2003 to June 2008. Besides being a sensitive experiment on 130Te double beta decay, CUORICINO is a conclusive test of CUORE. CUORICINO provided important results concerning both the technical performances of the bolometric tower (CUORE will be made of 19 such towers), the background level .In particular, one of the information gained is that the most probable candidates for the continuum background observed in the spectra, are the surface α contaminations of the copper mounting frame. Silicon Barrier Detectors (SBD) are a powerful instrument to study charged particle radiation (like α particles). During my PHD one of the activity I focused on was the optimization of the SBD used in the radioactivity laboratoty of the the University of Milano Bicocca A complete procedure for the calibration of these detectors was set- tled. In fact, one of the main problem to face with, (due also to the extremely low activity measured), is the discrimination of their intrinsic background level from that of the sample measured. The SBD are always operated in Ultra Low Background vacuum chambers. In the context of the discrimination of the background, evaluation of the muon and shower contribution to the acquired spectra were performed. The latter were done through a coincidence measurement between the SBD and a scintillator. The result of the measurements and of their ananlysis showed that the major contribution to the spurious counts comes from the showers. A dedicated acquisition was done for the detectors, with a module which lets to have event’s temporal imformation. To give limits on the surface activities of the samples the use of Monte Carlo (MC) simulation is mandatory in order to have an estimation of the efficiency of energy detection. The use of the MC simulation was optimized: different depht and profiles of contamination were studied and tested. This optimization allows to give limits on surface 232Th, 238U and 210Pb-Po activities which depend on the depht of contamination. The drastic reduction of the sensitivity achieved (from 10−5 to 10−7 and 10−8 Bq · cm2 fo the cleanest material measured) is due to the described optimiza- tion. Last, but non least, the SBD measurements played a crucial role in the material selection, depending on the radiopurity required, for the CUORE experiment. Concering the ββ0ν, a crucial role, in the theoretical interpretation of the experimental result, is played by the Nuclear Matrix Element (NME) used to transalte the observed rate (in the energy region where the signal is expected) in a sensitivity on the effective neutrino mass |mν|. I performed a study in order to compare and understand the different nuclear models used nowadays, and the respective Phase Space Factors (PSF) used. This study allows to compare, in a quantitative way, the different experiments on neutrinoless double beta decay. A database was realized in which all the inputs are collected, comments and references on NME and PSF are illustrated and the kind of short range correlation is used in the calculation of the matrix element. The database, with the information collected and properly organized, allows to evaluate the sensitivity on |mν| of all the experiments now at work, depending on the nuclear model used. The difficulties encountered in the comprehension of the nuclear models and in the PSF used are due to three main reasons. • the PSF shoul be in principle standard and unambiguous, not depending on the nuclear model, but just on the initial and final states JP . This is not what the study showed: the PSF, in the different formulation, show discrepancies of a factor 5 or 6. • the nuclear models assume different approaches to the process and should lead to different results. Two models, i.e., the Shell Model and the IBM (Interactive Boson Model) have a similar approach, but they differ in handling the states which are ’far from closed shells’, so in the handling of the nuclear deformations. The QRPA, (in the version pnQRPA an rQRPA, Quasi Random Phase Approximation), have a different approach to the previous models, because it introduces the concept of quasiparticle, which are states built with a ’mixing’ of creation and annihilation operators (a theory very similar to BCS for the superconductivity) and it leads to a correlation between particles and holes and not just between particles (gph and not only gpp pairing). • the SRC (shot range correlation) used should be univocal, but this is not the case. The theoreticians don’t give a clear choice of the proper SRC to be used. Finally I performed a study on the electron decay, in the channel e− ← γ + ν, using CUORICINO data. Moreover I performed a calculation of the cross section for the process, assuming a massless neutrino in the first step and a massive neutrino in the second step. The study of the channel implies to evaluate the signature of the decay, which depends on the material and atomic shell from which the electron disappears. In fact the visible energy changes if the decay happens in the active volume of the detector or in the surroinding materials: Ev = (mec2−Eb) 2 + EX = (mec2+Eb) 2 where me is the electron mass, Eb is the binding energy, EX is the X-ray energy following the decay. The last term is included only if the decay happens inside the active volume of the detectors. Thus, there are several signatures which can be discriminated from the background only if the detector resolution is excellent. Moreover the doppler broadening of the lines, due to the orbital motion of the electron in the shell, must be considered. I thus studied the different signatures in several materials, (potential emitters). In the analysis I included the efficiences for the signatures, using Monte Carlo simulations, expressely conformed to experimental set-up and charachteristics (such as real thresholds, active channels). The correction to the efficiencies, i.e. the loss of ’good events’, due to the analysis cuts, was evaluated. All the analysis done led to a promising result for this decay, in competition with the current limits given from other collaborations. The cross section calculation allowed to give an estimation of the CNC parameter, using as inputs the available experimental data.

Neste trabalho foram desenvolvidos detectores de radiação Barreira de superfície de silício que fossem capazes de detectar a presença da radiação gama de baixa energia proveniente de sementes de iodo-125 utilizada em tratamentos de braquiterapia. A partir de substratos comerciais de silício foram desenvolvidos os detectores, de uma sequência que partiu de tratamentos químicos nas superfícies destes substratos com a intenção de minimizar os possíveis ruídos gerados, validação das amostras obtidas como diodos, assegurando características detectoras, e a efetiva utilização como detector para fontes radioativas de iodo-125 com energia em torno de 25 kev e amerício-251 com energia na ordem de 59 kev. Finalizou realizando a análise dos espectros de energia obtidos e assim foi possível observar a capacidade destes detectores para mensuração da energia proveniente destas sementes.
In this work it was developed radiation detectors silicon surface barrier that were capable of detecting the presence of gamma radiation from a low energy of iodine-125 seeds used in brachytherapy treatments. From commercial silicon substrates detectors were developed, one sequence left of chemical treatments to the surfaces of these substrates with the intention of minimizing the possible noise generated, validation of the samples obtained as diodes, ensuring detector characteristics and effective use as detector for iodine-125 radioactive sources with energy of about 25 kev and americium-251 with energy on the order of 59 kev. Finished performing the analysis of the obtained energy spectra and so it was possible to observe the ability of these detectors to measure the energy from these seeds.

Ce travail de thèse visait à étudier les potentialités du silicium poreux comme support d'un élément sensible pour les capteurs de gaz. Afin de comprendre les mécanismes de formation du silicium poreux nous avons eu recours à l'électrochimie fondamentale de silicium. Ainsi, les mesures I-V de l'interface silicium/solution d'acide fluorhydrique ont mis en évidence deux mécanismes compétitifs : la formation électrochimique de l'oxyde de silicium et sa dissolution par HF. De même, la nature de l'oxyde de silicium est discutée dans le cadre des diagrammes d'équilibres tension-ph du système silicium-eau. Dans le but de développer de nouveaux capteurs de gaz, nous avons élaboré des couches de silicium poreux modifiées ultérieurement par un métal catalytique. Dans le cas des structures de type diode (Pd/Sp/Si), l'épaisseur de la couche de silicium poreux contrôle les processus de transport de courant. La quantité du palladium déposée influe beaucoup sur la sensibilité des structures sous gaz. Ainsi, ce sont les structures avec une couche ultramince de palladium qui présentent les meilleures réponses à l'hydrogène. En s'appuyant sur le modelé d'une hétérojonction métal/silicium poreux/si ayant une couche mince de silicium poreux, nous avons relie ce phénomène a la variation des porteurs libres de la zone de charge d'espace du silicium. La mesure de la différence de potentiel de contact nous a permis d'étudier l'effet de l'adsorption d'hydrogène sur la surface de palladium supporte sur du silicium poreux. Malgré nos attentes, les structures a base du silicium poreux ont montré une faible amélioration de la sensibilité par rapport aux structures traditionnelles Pd/SiO2/Si. Par contre, elles étaient plus performantes en ce qui concerne la cinétique, donc le temps de réponse deux fois plus rapide.

This paper reviews the progress in the development of infrared image sensors with Schottky-barrier detectors (SBDs). Schottky-barrier focal plane arrays (FPAs) are infrared imagers that are fabricated by a well established silicon VLSI process; therefore, at the present time they represent the most advanced technology for large-area high-density focal plane arrays for many SWIR (1 to 3 μm) and MWIR (3 to 5 μm) applications. SBD line sensing arrays with up to 4096 × 4 elements and 2048 × 16 TDI elements were developed, and SBD staring (area) arrays with up to 1040 × 1040 elements have been reported. PtSi SBDs represent the most established SBD technology for applications in the SWIR and MWIR bands. At an operating temperature of 77 K, the dark current density of PtSi SBDs is in the range of 1.0 to 4.0 nÅ/cm2. Pd2Si SBDs were developed for operation with passive cooling at 120 K in the SWIR band. IrSi SBDs have also been investigated to extend the application of Schottky-barrier FPAs into the LWIR (8 to 10 μm) spectral range. Because of very low readout noise, the IR-CCD imagers with PtSi SBDs that have quantum efficiency of 0.5% to 1% at 4.0 μm are capable of 300-K thermal imaging with a noise equivalent temperature (NEΔT) from 0.033 to 0.15 K for operation at 30 frames/s and f/1.0 to f/2.8 optics.

For the first time to our knowledge a single crystal, thin film III—V metal-semiconductor-metal (MSM) detector that has the Schottky metal contacts between the absorbing semiconductor material and the host substrate (glass and silicon) has been demonstrated. The MSM is formed by metallizing the smooth host substrate, placing the thin film epitaxial lift-off compound semiconductor material on top of the metal, and post annealing to form the Schottky barriers. This integration technology is important because there is no metal directly deposited onto the III—V compound semiconductor, and hence no contact definition and alignment step needs to be performed on the GaAs. The interdigitated contacts, which lie between the absorbing layer and the host substrate, eliminate finger shadowing, thereby potentially increasing the efficiency of the device. The extension of this work will ideally lead to inexpensive manufacturing processing for optoelectronic integrated circuits in which Si integrated circuitry will only need a final compound semiconductor device alignment, attach, and anneal step for optoelectronic detector integration.