Search

Цель этой работы заключается в том, чтобы Ð¾Ñ Ð°Ñ€Ð°ÐºÑ‚ÐµÑ€Ð¸Ð·Ð¾Ð²Ð°Ñ‚ÑŒ радиационную стойкость последней партии детекторов, Ð¿Ñ€Ð¾Ð¸Ð·Ð²ÐµÐ´ÐµÐ½Ð½Ñ‹Ñ Â«FondazioneBrunoKessler» (FBK):UFSD3.2 и HamamatsuphotonicsK.K. (HPK): HPK-P2, сравнив Ð¸Ñ Ð²Ð¾Ð»ÑŒÑ‚-фарадные Ñ Ð°Ñ€Ð°ÐºÑ‚ÐµÑ€Ð¸ÑÑ‚Ð¸ÐºÐ¸ до и после адронного облучения при Ñ€Ð°Ð·Ð½Ñ‹Ñ Ñ„Ð»ÑŽÐµÐ½ÑÐ°Ñ . Тесты устойчивости показали приблизительные значения радиационной стойкости к адронному облучению. Исследования отжига продемонстрировали положительные эффекты этого процесса на дефекты, вызванные радиацией. Метод Ð¿ÐµÑ€ÐµÑ Ð¾Ð´Ð½Ñ‹Ñ Ñ‚Ð¾ÐºÐ¾Ð² был использован, чтобы определить функциональность детекторов после облучения, а также, чтобы определить междетекторные расстояния в Ð¾Ð±Ñ€Ð°Ð·Ñ†Ð°Ñ Ð¸ вычислить коэффициент заполнения. Некоторые из Ð¿Ð¾Ð»ÑƒÑ‡ÐµÐ½Ð½Ñ‹Ñ Ñ€ÐµÐ·ÑƒÐ»ÑŒÑ‚Ð°Ñ‚Ð¾Ð² были сравнены с измерениями Ð¿Ñ€ÐµÐ´Ñ‹Ð´ÑƒÑ‰Ð¸Ñ Ð¿Ð°Ñ€Ñ‚Ð¸Ð¹ детекторов HPK и FBK, с целью оценивания улучшения нового поколения детекторов. Все измерения и связанные с ними действия были проведены в Детекторной Лаборатории Физического Института Хельсинки, в качестве члена исследовательской группы обновления Компактного Мюонного Соленоида., The objective of this work was to characterize the radiation hardness of the Fondazione Bruno Kessler (FBK) Ultra-Fast Silicon Detectors (UFSD) UFSD3.2 and the Hamamatsu photonics K.K. (HPK-P2) batches by comparing their capacitance-voltage characteristics before and after hadron irradiation at different fluence values. Stability tests gave an estimate of the hadron radiation hardness and the annealing studies showed the effect of beneficial annealing on the radiation damage. Transient current technique (TCT) was utilized to determine the operability of the sensors after the irradiation, and it was also used for determining the interpad distances and fill factor. Some of the results were compared with measurements from the previous HPK sensor batch and with previous measurements from FBK UFSD3.1 batch, with the objective of getting an estimate of the detectors enhanced performance. All measurements and related activities were carried out at the Helsinki Institute of Physics (HIP) Detector Laboratory as a member of the Compact Muon Solenoid (CMS) upgrade research group.

The drift behavior of charge carriers, generated by 𝛼�-particles of a reference 241Am-source, in electronic grade, single crystal chemical vapor deposition (scCVD) diamond was investigated by the transient current technique (TCT) from room temperature up to ≈ 473 K. Furthermore, the 𝛼�-spectroscopic behavior was analyzed in terms of charge collection and spectroscopic resolution for the same temperature range. All conducted measurements revealed complete charge collection up to the maximum temperature. The electron–hole-pair creation energies were derived from the TCT as well as from the spectroscopic measurements. The herein presented results imply that high temperature 𝛼�-spectroscopy with diamond-based semiconductor solid state detectors, using presently available scCVD sensor substrates, is feasible at least up to 473 K. Only at the highest applied temperature, the conducted TCT measurements showed distorted signal traces, indicating a uniform positive space charge built-up., Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 989, ISSN:0168-9002, ISSN:1872-9576

The Two Photon Absorption Transient Current Technique (TPA-TCT) is a tool to characterize semiconductor detectors using a spatially confined laser probe. Excess charge carriers are produced by the simultaneous absorption of two sub-bandgap photons in the material. The current induced by the motion of carriers is studied using well known TCT systems. Differently to standard TCT where the energy deposition (pair creation) is continuous along the beam, TPA-TCT reduces this region to an ellipsoidal volume, achieving thus, true 3D spatial resolution. This paper gives an overview of the technique and shows its performance in irradiated detectors, in particular diodes and High Voltage CMOS detectors., This work was performed in the framework of the CERN-RD50 collaboration under the projects 2016-04, 2017-02. Activity partially supported by the Spanish Ministry of Science grants FPA2015-71292-C2-2-P and FPA2017-85155-C4-1-R; and the European Union’s Horizon 2020 Research and Innovation program under Grant Agreement no. 654168 (AIDA-2020).

The requisites at the Large Hadron Collider (LHC) at CERN have driven silicon tracking detectors to the fringe of the modern technology. The next upgrade of the LHC to a 10 times increased luminosity of 7.5×10 cm s will require semiconductor detectors with substantially improved radiation hardness. CERN-RD50 collaboration mandate is to provide detector technologies, which are able to operate in such an environment. Within this context, this paper describes the approaches and first results of a C++11 multi-threading software based on the Shockley–Ramo's theorem to simulate non-irradiated and irradiated silicon micro-strips and pad detectors of complex geometries in order to understand signal formation and charge collection efficiencies of arbitrary charge distributions., This work was performed in the framework of the CERN-RD50 collaboration. This project has been partially supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under grant number FPA2013-48387-C6-1-P and FPA2015-71292-C2-1-P.

This thesis is focused on study of charge transport in semiconducting radiation detectors. Theoretical calculations of current waveforms based on continuity equation and drift-diffusion equation are done. Useful approximations of current waveforms for detector with shallow electron trap are discussed. Monte Carlo simulation of the current waveforms is proposed and applied to fit experimental current waveforms measured using laser-induced transient current technique and for evaluation of charge transport parameters of the detector such as electric field profile, trapping and detrapping time of traps, drift mobility and other parameters. Detectors prepared from semi-insulating GaAs and CdZnTe single crystals are tested using electrical, spectroscopic and optical characterization techniques.

For the first time, the deep n-well (DNW) depletion space of a High Voltage CMOS sensor has been characterized using a Transient Current Technique based on the simultaneous absorption of two photons. This novel approach has allowed to resolve the DNW implant boundaries and therefore to accurately determine the real depleted volume and the effective doping concentration of the substrate. The unprecedented spatial resolution of this new method comes from the fact that measurable free carrier generation in two photon mode only occurs in a micrometric scale voxel around the focus of the beam. Real three-dimensional spatial resolution is achieved by scanning the beam focus within the sample., This work was performed in the framework of the CERN-RD50 collaboration under the project RD50-2015-03. The project has received funding from the European Commission under the FP7 Research Infrastructures project AIDA, grant agreement no. 262025. This project has been partially supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under grant number FPA2013-48387-C6-1-P.

High resistivity and high oxygen concentration of silicon wafers can be beneficial for the radiation hardness of silicon detectors. Wafers of Magnetic Czochralski silicon (MCz-Si) can be grown with a resistivity of a few k Ω cm and with well-controlled, high oxygen concentration. According to the beam test results presented in this paper, n-type MCz-Si bulk, p-strip readout detectors with can be operated with acceptable signal-to-noise ratio up to the irradiation fluence of 1×1015 cm−2 1-MeV neutron equivalent. The improved radiation hardness compared to that of traditional p-in-n Float Zone silicon (p-in-n FZ-Si) detectors can be explained by better electric field distribution inside MCz-Si detectors. The difference between the distributions is clearly shown by Transient Current Technique (TCT) measurements, presented in this paper. Thus, strip detectors made on n-type MCz-Si are a feasible option for the outer tracker layers of the potential upgrade of the Large Hadron Collider (LHC), the Super-LHC. This corresponds approximately 95% of the total area of silicon detectors in the Super-LHC.

Semi-insulating gallium arsenide (SI-GaAs) detectors, in the form of Schottky diodes, have been irradiated from the front or from the back contact or from the side, with light pulses from picosecond laser source, tunable in the range of 780–1020 nm and focused to a 50–100 μm spot on the surface of the detector. Energy per pulse was in the range of 4–25 pJ, with a 10 or 100 Hz repetition rate. Each pulse mimics the interaction of a single energetic particle with the substrate, but with a photon mean free path modulated in the range of 1 μm–1 cm, depending on the light wavelength. The SI-GaAs substrates have a thickness of 200 μm (VGF grown), or 600 μm (LEC) or 1000 μm (VGF). The time response of the detectors, analysed with the Transient Current Technique (using a fast digital sampling oscilloscope) in terms of peak signal amplitude and charge rise time, has been evaluated as a function of: reverse voltage bias (50–1200 V), light wavelength (780–1020 nm), side position between the electrodes, position on the front contact. The results are: (1) the shape of the transient current signal may show the presence of two peaks, about 1 ns apart; (2) the charge rise time, considered to be dominated by the charge collection time, is between 2 and 13 ns; (3) the charge rise time, as due to electron drift or hole drift in the region between the contacts, has been measured as 2–5 ns, also dependent on the applied bias; (4) the transient current (exponential) decay time, for front or back irradiation, increases with the bias voltage up to 2–20 ns and these data are considered to be consistent with the electron detrapping time; (5) under reverse bias, for 1 mm pad side and a large ohmic contact on the back, the electric field extends around the front contact up to about 200 μm.

Current pulses produced by absorption of picosecond near-infrared light pulses have been used in order to analyze the shape of the electric field and charge transport properties in semi-insulating (SI) GaAs Schottky barrier X- and gamma-ray detectors. Diodes with square pads of side 0.2–1 mm on 200, 600 and 1000-μm-thick SI GaAs substrates have been illuminated from the front (Schottky) contact, from the back (ohmic) side and laterally between the contacts. Current pulses have been recorded with a fast digital sampling oscilloscope, at room temperature, without using any signal amplification. Current and charge pulse shapes have been analyzed as a function of reverse bias voltage, positioned on the detector surface and optical wavelength around the near-infrared absorption edge of GaAs. The wavelength tuning allows for increasing light penetration lengths. Signal analysis gives the peak current, total collected charge and the charge collection time, which are related to the average strength of the electric field and the drift velocity field, while pulse shape depends on the local value of these fields. The experimental results show that a complete detector characterization is feasible with this optical technique, in a manner analogous to that commonly done with gamma- or X- or alpha-ray sources, with the advantage of analyzing the charge collection time. An additional advantage is represented by focusing the light beam on the detector surface, for 1D or 2D scan.

Single crystal chemical-vapour deposition (scCVD) diamonds are interesting for a wide range of applications. For many of them a good understanding of the temperature dependence of charge carrier transport mechanisms and properties is crucial. Measurements on the temperature dependence of charge carrier movement in scCVD diamond semiconductor detectors are presented. The evolution of the pulse shape of the detector response from impinging α particles is measured as a function of temperature employing the α-induced transient current technique (α-TCT) within a temperature range from 67 K to 295 K. The measurements are used to extract the drift mobility, drift velocity, and saturation velocity, in terms of which the results are interpreted.

This thesis aims at demonstrating a novel technique for the characterization of interfaces obtained by a CMOS-compatible Surface Activated Bonding (SAB) process between silicon wafers. This enables the optimization of the two main components of monolithic silicon detectors, the CMOS circuitry for the read-out and the sensing layer, by fabricating them in different substrates and then by bonding them together. Therefore, to be collected by the read-out circuitry, charges generated by radiation in the bulk have to traverse the bonding interface, whose electrical properties need to be characterized. The first part of this thesis is focused on the evaluation of Transient Current Technique (TCT) for this purpose. TCT is largely used for the study of radiation damage in silicon detectors, and consists in the injection of a localized cloud of electrons inside a detector based on a reverse-biased diode, that is drifted by the electric field. A transient current signal is generated, whose shape is related to the electric field profile that may be affected by lattice defects generated by radiation. In this context, the bonding process is expected to generate a thin amorphous silicon interface between the two bonded substrates. This layer can be seen as full of defects and therefore it is expected to influence the electric field, and the TCT current signal. This is demonstrated by means of Sentaurus TCAD numerical simulations and an analytical model, using a diode with the bonding interface in the middle of the bulk as test structure. The second part of the thesis describes the characterization of the interface, generated by bonding high resistivity wafers at CEA-Leti in Grenoble. For this purpose, Schottky diodes are fabricated on these stacks at EPFL, and then characterized with CV, IV and TCT techniques. The results obtained are compared to simulation data, to show that the electric field did not extend to the bulk, preventing charges to be collected. This is an issue for the fabrication of radiation detectors, since there would not be collection of charges generated at the sensing bulk. Following these conclusions, two solutions are proposed. First, the optimization of the bonding process to reduce the number of traps. Second, a modification of the detector design in such a way that the bonding interface is located at the PN junction, since the electric field is maximum at this position, and therefore the influence of traps is less important. The last part of this thesis is devoted to the description of a new charge injection technique for TCT measurements. Instead of using a laser, charges are injected by means of nanosecond voltage pulses, applied to dedicated wells fabricated on the PN junction contact. Injection occurs by thermionic emission, while the charges drift, as in standard TCT measurements. This novel method of charge injection is called electrical injection TCT (el-TCT). It could allow to perform on-line TCT measurements during experiments.