[en] A deep knowledge of the fundamental physics phenomena involved in Silicon Detectors is mandatory for their optimal use in dedicated applications. In the present manuscript, this concept is represented for the particular case of two types of Silicon Detectors: (1) the Silicon Photomultipliers (SiPM) and their applications in medical imaging and (2) the Planar Pixel Sensors (PPS) and their application for the upgrade of the ATLAS inner detector at high-luminosity LHC. My personal work on SiPM detectors started around 10 years ago. Therefore, the first part (A) of my HDR will firstly relate the physical principle of the Geiger-Mode Avalanche Photodiodes (GM-APD), representing the elementary cell of a SiPM detector. Then, the concept of the SiPM detector is introduced and its main physical characteristics are reviewed. The experimental set-ups developed for the measurement of these detectors as well as the SiPM characteristics from main producers are presented. Since the temperature dependence of SiPM parameters represents a particular drawback in different applications, my dedicated work on this subject is also presented showing that this dependence can become negligible if the operating conditions are well controlled. The SiPM detectors present important electrical, optical and mechanical advantages allowing for flexible design in applications where large detection area is required. Therefore, they are very 'appetizing' devices for medical imaging applications and my work on using SiPM arrays in two medical applications is also presented: high resolution small animal PET scan and hand-held radiation detector for assisting the surgeon in locating and removing the solid tumors. In parallel with the SiPM activity, in the last years I was involved in the design and characterization of new PPS detectors for the upgrade of the ATLAS inner detector at high luminosity LHC. Therefore, the second part (B) of my HDR details the experimental methods like Secondary Ion Mass Spectrometry (SIMS) and Spreading Resistance Profiling (SRP) used for the doping profiles measurements of PPS detectors. The importance of these measurements for the fabrication process control and the calibration of the Technology-Computed Aided Design simulations (TCAD) are shown. Simulations results predicting the behavior of new planar pixel sensors with improved geometrical and radiation hardness characteristics for the upgrade of the ATLAS inner detector at high-luminosity LHC are also presented

[en] Electric field magnitude and depletion in the bulk of silicon pixel detectors, which influence its breakdown behaviour, was studied using finite-element method to solve the drift-diffusion equation coupled to Poisson's equation in a simplified two dimensional model of the ATLAS pixel sensor. Based on this model, the number of guard rings and dead edges width were modified to investigate their influence on the detector's depletion at the edge and on its internal electrical field distribution. Finally, the 3 level model was implemented into the simulation to study the behaviour of such detector under different level of irradiation.

[en] The LHC accelerator complex will be upgraded between 2020–2022, to the High-Luminosity-LHC, to considerably increase statistics for the various physics analyses. To operate under these challenging new conditions, and maintain excellent performance in track reconstruction and vertex location, the ATLAS pixel detector must be substantially upgraded and a full replacement is expected. Processing techniques for novel pixel designs are optimised through characterisation of test structures in a clean room and also through simulations with Technology Computer Aided Design (TCAD). A method to study non-perpendicular tracks through a pixel device is discussed. Comparison of TCAD simulations with Secondary Ion Mass Spectrometry (SIMS) measurements to investigate the doping profile of structures and validate the simulation process is also presented

No abstract available

[en] The high-energy ion irradiation represents one of the perspective methods for modification of semiconductor materials. The first results regarding the effect of irradiation with high-energy ions on depth profiles of electrically active impurities (Al, As, Sb, Ga, Bi) in silicon have been presented. The aim of the present work is the study of modification of boron profile in silicon after irradiation with Kr, Xe and Bi ions with energies in the range 3 to 5 MeV/amu. The <111> n-type silicon wafers, implanted with 140 keV boron ions up to a dose of 2 x 10¹⁵ cm^-2 have been used in our experiments. These wafers have been irradiated with Kr (245 MeV and 305 MeV), Xe (600 MeV) and Bi (710 MeV) ions with fluxes ranging from 10¹¹ to 10¹³ cm^-2. After high-energy ion irradiation the thermal annealing of the samples has been carried out in nitrogen ambient at 800, 900, 1000 and 1100 deg. C for 30 minutes. The study of boron profiles has been performed with secondary ion mass spectrometry and spreading resistance methods. The results of present investigations showed that the high-energy ion irradiation, even at relatively low doses of about 10¹¹ cm^-2, provides a considerable redistribution of boron in silicon in comparison with reference samples. Typical example of this effect, enhanced by high-energy ions is presented. In the analysis of the obtained results, the main attention is focussed on the next questions: - the role of electronic and nuclear stopping processes of high-energy heavy ions in forming radiation damage in silicon; - the effect of high electronic energy loss (higher than 10 keV/nm) on dopant redistribution in silicon; - the dependence of diffusion parameters of boron on the concentration of defects created in silicon by high-energy heavy ions. (authors)

[en] This work reports on the development of an electro-optical set-up for the characterization of the Silicon PhotoMultiplier (SiPM) devices as well as on the comparative study of the characteristics of different SiPM prototypes. The electrical set-up allows the measurement of the static (breakdown voltage, overvoltage quenching resistance) and dynamic (gain, dark count rate) characteristics. The optical set-up allows the estimation of the photon detection efficiency as a function of the wavelength and the operation voltage. The comparative study has been performed on SiPM devices covering an area of 1x1 mm² and supplied during 2007 by Photonique S.A. (Switzerland), FBK-irst (Italy), SensL (Ireland) and Hamamatsu (Japan).

[en] This work reports on Silicon Photomultipliers (SiPM) timing resolution measurements performed at the picosecond level at Laboratory of Linear Accelerator (LAL), In2p3- CNRS. The dependence of Single Photoelectron Timing Resolution (SPTR) with the applied voltage, wavelength of the light and the temperature was measured for detectors from Hamamatsu Photonics, AdvanSiD and Sensl with an active area of 1 and 9 mm². The SPTR improves with the bias voltage increase. No significant variation of SPTR was observed with the temperature change. We also observed a weak variation of it as a function of the wavelength of the light. The best SPTR measured was about 120 ps (FWHM).

[en] Excited states up to E_x=2.0 MeV in ⁷³ As have been investigated with the ⁷³ Ge (p,nγ) reaction at incident energies of 3.15, 4.0 and 4.5 MeV. Lifetimes of twelve levels have been determined by Doppler Shift Attenuation method. A comprehensive analysis of the structure of ⁷³ As has been performed within the IBFA model. Multi-shell calculations (1f_7/2, 2p_3/2, 1f_5/2, 2p_1/2, 1g_9/2 and 2d_5/2 proton orbitals coupled to a ⁷² Ge core) have been performed and compared to the existing experimental information: excitation energies, J^π values, absolute electromagnetic transition probabilities, branching ratios and one-proton pickup and stripping spectroscopic factors. A reasonable agreement has been obtained for a large number of levels. A comparison of the experimental and calculated levels is given. (authors)

[en] An experimental investigation of the structure of ⁷¹ Ge has been undertaken at the FN Tandem Van de Graaff accelerator of IFIN-HH. The reaction ⁷¹ Ga(p,nγ) has been used to populate levels in the ⁷¹ Ge nucleus and deduce level lifetimes through the DSA (Doppler Shift Attenuation) method. The reaction has been performed at the incident energies of 2.5, 3.1 and 3.5 MeV, close to the threshold of the levels of interest. The beam intensities were around 10 nA. The target was a pellet of isotopically enriched ⁷¹ Ga stuck to a tantalum foil and cooled; its thickness was about 30 mg/cm². The gamma rays were detected with a 20% efficiency HPGe detector of 2.2 keV FWHM resolution at 1.33 MeV, placed at 30 cm from the target, at angles between 0 angle and 142 angle with respect to the beam axis. The variation of the energy of the peak centroid of the transitions of interest with the detection angle led to the experimental attenuation factor F_exp(τ). The stability of the energy calibration of the spectrometer was better than the precision in the centroid determinations and was continuously monitored with radioactive sources and activation lines. In evaluating the F(τ) data, we have used different stopping powers estimations. Since for all levels the observed shifts are rather small, close to the limit of method's sensitivity, the measurements have been repeated recently with better energy resolution and special care for the stability of the electronics. A table is given containing the ⁷¹ Ge energy levels (from 808.1keV to 1792.2 Kev), the γ ray transitions, the attenuation factors and the corresponding life-times. (authors)

[en] This work reports on the behavior of the Multi-Pixel Photon Counter (MPPC) detectors produced by Hamamatsu HPK in a temperature range from +55 °C down to −175 °C. Devices of 1×1 mm"2 and 3×3 mm"2 total area and 50×50 μm"2 μcell size have been studied. Electrical parameters such as breakdown voltage, gain, capacitance, pulse shape, quenching resistance and dark count rate were measured and some of them showed important temperature variation. Besides this temperature dependence, it is shown that MPPC detectors can operate with a stable gain independent of T if the overvoltage is kept constant. Moreover, at a given temperature, the device of 3×3 mm"2 (production year 2011) presents seven times less dark rate/mm"2 with respect to the one of 1×1 mm"2 (production year 2007), showing an important technological improvement implemented by HPK during four year's time interval