This doctorate thesis focuses on the analysis, design and characterization of Radio-Frequency (RF) Micro-Electro-Mechanical System (MEMS) switches for space applications. The work was inspired and supported by the European Space Agency (ESA) Contract No. ITT AO/1-5288/06/NL/GLC ?High Reliability Redundancy Switch?. The main purpose of the project is the design and realization of high-reliability RF MEMS switches for satellite payload redundancy networks. Up to now, the common satellite architecture implements redundancy networks by means of bulky devices. RF MEMS switches allow for extremely miniaturized networks along with outstanding performances in terms of losses, power consumption and linearity, not really achievable with solid state devices. As requirements for such an application, RF MEMS switches have to survive under extremely harsh environmental and operating conditions. In particular the device should handle continuous bias voltage (at least for 10 years), 5 W of RF input power and around 1000 actuation cycles without meaningful electrical and mechanical failure. The thesis proposes novel mechanical solutions to accomplish this task, exploiting active restoring mechanisms able to restore the previous status of switch in case of reversible failure. This work also provides a deep insight on the main reliability aspects of a RF MEMS device such as dielectric charging, contact degradation and power handling.

A methodology for designing Wireless Camera Network nodes featuring long lifetime is presented. Wireless Camera Networks may nd widespread application in the elds of security, animal monitoring, elder care and many others. Unfortunately, their development is currently thwarted by the lack of nodes capable of operating autonomously for a long period of time when powered with a couple of AA batteries. In the proposed approach, the logic elements of a Wireless Camera Network node are clearly identied along with their requirements in terms of processing capabilities and power consumption. For each element, strategies leading to significant energy savings are proposed. In this context, the employment of a custom vision sensor and an ecient architecture are crucial. In order to validate the methodology, a prototype node is presented, mounting a smart sensor and a ash-based FPGA. The node implements a custom algorithm for counting people, a non trivial task requiring a considerable amount of on-board processing. The overall power consumption is limited to less than 5 mW, thus achieving a two orders of magnitude improvement with respect to the state of the art. By powering the system with two batteries providing 2200 mAh at 3.3 V, the expected lifetime of the system exceeds two months even in the worst-case scenario.

In several application fields there is an increasing need for a diffused on-field control of parameters able to diagnosis potential risks or problems in advance or in early stages in order to reduce their impact. The timely recognition of specific parameters is often the key for a tighter control on production processes, for instance in food industry, or in the development of dangerous events such as pollution or the onset of diseases in humans. Diffused monitoring can be hardly performed with traditional instrumentation in specialised laboratories, due to the time required for sample collection and analysis. In all applications, one of the key-points for a successful solution of the problem is the availability of detectors with high-sensitivity and selectivity to the chemical or biochemical parameters of interest. Moreover, an increased diffused on-field control of parameters can be only achieved by replacing the traditional costly laboratory instrumentations with a larger number of low cost devices. In order to compete with well-known and established solution, one of main feature of new systems is the capability to perform specific tests on the field with fast response times; in this perspective, a fast measurement of reduced number of parameters is to be preferred to a straightforward “clone†of laboratory instrumentation. Moreover, the detector must also provide robustness and reliability for real-world applications, with low costs and easiness of use. In this paradigm, MEMS technologies are emerging as realisation of miniaturised and portable instrumentation for agro-food, biomedical and material science applications with high sensitivity and low cost. In fact, MEMS technologies can allow a reduction of the manufacturing cost of detectors, by taking advantage of the parallel manufacturing of large number of devices at the same time; furthermore, MEMS devices can be potentially expanded to systems with high level of measurement parallelism. Device costs are also a key issues when devices must be for “single use†, which is a must in application where cross-contamination between different measurement is a major cause of system failure and may cause severe consequences, such as in biomedical application. Among different options, cantilever micro-mechanical structures are one of the most promising technical solution for the realisation of MEMS detectors with high sensitivity. This thesis deals with the development of cantilever-based sensor arrays for chemical and biological sensing and material characterisation. In addiction to favourable sensing properties of single devices, an array configuration can be easily implemented with MEMS technologies, allowing the detection of multiple species at the same time, as well as the implementation of reference sensors to reject both physical and chemical interfering signals. In order to provide the capability to operate in the field, solution providing simple system integration and high robustness of readout have been preferred, even at the price of a lower sensitivity with respect to other possibilities requiring more complex setups. In particular, piezoresistive readout has been considered as the best trade-off between sensitivity and system complexity, due to the easy implementation of readout systems for resistive sensors and to their high potential for integration with standard CMOS technologies. The choice has been performed after an analysis of mechanical and sensing properties of microcantilever, also depending of technological options for their realisation. As case-studies for the development of cantilever devices, different approaches have been selected for gas sensing applications, DNA hybridisation sensing and material characterisation, based on two different technologies developed at the BioMEMS research unit of FBK (Fondazione Bruno Kessler - Center for Materials and Microsystems, Trento). The first process, based on wet-etching bulk micromachining techniques, has provided 10 µm-thick silicon microcantilevers while the second technology, based on Silicon-On-Insulator (SOI) wafer, has provided a reduction of device thickness, thus resulting in an increase of sensitivity. Performances of devices has been investigated by analytical and numerical modelling of both structures and readout elements, in order to optimise both fabrication technology and design. In particular, optimal implant parameters for the realisation of piezoresistors have been evaluated with process simulation with Athena Silvaco simulation software, while ANSYS has been used to analyse the best design for devices and the effect of some technology-related issues, such as the effect of underetch during the release of the beams or residual stresses. Static and modal analysis of cantilever bending in different conditions have been performed, in order to evaluate the mechanical performances of the device, and later results have been compared with the experimental characterisation. With regard to gas sensing applications, the development has been oriented to resonant sensors, where the adsorption of analytes on a adsorbent layer deposited on the cantilever leads to shift of resonance frequency of the structure, thus providing a gravimetric detection of analytes. The detection of amines, as markers of fish spoilage during transport, has been selected as a case-study for the analysis of these sensors. The sensitivity of devices has been measured, with results compatible with the models. Cantilever structures are also suitable for bioaffinity-based applications or genomic tests, such as the detection of specific Single Nucleotide Polymorphisms (SNPs) that can be used to analyse the predisposition of individuals to genetic-based diseases. In this case, measurements are usually performed in liquid phase, where viscous damping of structures results in a severe reduction of resonance quality factor, which is a key-parameter for the device detection limit. Then, cantilever working in “bending mode†are usually preferred for these applications. In this thesis, the design and technologies have been optimised for this approach, which has different requirements with respect to resonant detectors. In fact, the interaction of target analytes with properly functionalised surfaces results in a bending of the cantilever device, which is usually explained by a number of mechanism ranging from electrostatic and steric interaction of molecules to energy-based considerations. In the case of DNA hybridisation detection, the complexity of the molecule interactions and solid-liquid interfaces leads to a number of different phenomena concurring in the overall response. Main parameters involved in the cantilever bending during DNA hybridisation has been studied on the basis of physical explanations available in the literature, in order to identify the key issues for an efficient detection. Microcantilever devices can play a role also in thin film technologies, where residual stresses and material properties in general need to be accurately measured. Since cantilever sensors are highly sensitive to stress, their use is straightforward for this application. Moreover, apart from their sensitivity, they also have other advantages on other methods for stress measurements, such as the possibility to perform on-line measurements during the film deposition in an array configuration, which can be useful for combinatorial approaches for the development of thin film materials libraries. In collaboration with the Plasma Advanced Materials (PAM) group of the Bruno Kessler Foundation, the properties of TiO2 films deposited by sputtering has been measured as a case study for these applications. In addiction to residual stress, a method for measuring the Young’s modulus of the deposited films has been developed, based on the measurement by means of a stylus profilometer of beam stiffness increase due to TiO2 film. The optimal data analysis procedure has been evaluated in order to increase the efficiency of the measurement. In conclusion, this work has provided the development of MEMS-based microcantilever devices for a range of different applications by evaluating the technological solutions for their realisation, the optimisation of design and testing of realised devices. The results validate the use of this class of devices in applications where high sensitivity detectors are required for portable analysis systems.

Time synchronization is of primary importance for the operation of wireless sensor networks (WSN): time measurements, coordinated actions and event ordering require common time on WSN nodes. Due to intrinsic energy limitations of wireless networks there is a need for new energy-efficient time synchronization solutions, different from the ones that have been developed for wired networks. In this work we investigated the trade-offs between time synchronization accuracy and energy saving in WSN. On the basis of that study we developed a power-efficient adaptive time synchronization strategy, that achieves a target synchronization accuracy at the expense of a negligible overhead. Also, we studied the energy benefits of periodic time synchronization in WSN employing synchronous wakeup schemes, and developed an algorithm that finds the optimal synchronization period to save energy. The proposed research improves state-of-the-art by exploring new ways to save energy while assuring high flexibility and reliable operation of WSN.

Recent advancements in biomedical research and imaging applications have ignited an intense interest in single-photon detection. Along with single-photon resolution, nanosecond or sub-nanosecond timing resolution and high sensitivity of the device must be achieved at the same time. Single- Photon Avalanche Diodes (SPADs) have proved their prospectives in terms of shot-noise limited operation, excellent timing resolution and wide spec- tral range. Nonetheless, the performance of recently presented SPAD based arrays has an issue of low detection efficiency by reason of the area on the substrate occupied by additional processing electronics. This dissertation presents the design and experimental characteriza- tion of a few compact analog readout circuits for SPAD based arrays. Tar- geting the applications where the spatial resolution is the key requirement, the work is focused on the circuit compactness, that is, pixel fill factor re- finement. Consisting of only a few transistors, the proposed structures are remarkable for a small area occupation. This significant advancement has been achieved with the analog implementation of the additional circuitry instead of standard digital approach. Along with the compactness, the dis- tinguishing features of the circuits are low power consumption, low output non-linearity and pixel-to-pixel non-uniformity. In addition, experimental results on a time-gated operation have proved feasibility of a sub-nanosecond time window.

The development of Fully Depleted Monolithic Active Pixel Sensors (FD-MAPS) represents nowadays a hot-topic in the radiation detector community. The advantages in terms of production costs and easiness of manufacturing in comparison to the state-of-the-art hybrid detectors boost the research effort in the direction of developing new CMOS compatible detector technologies. To this end, the INFN ARCADIA project targeted the design of a sensor platform for the production of FD-MAPS to be employed in different scientific, medical and space applications. The sensor technology has been developed in collaboration with LFoundry on the basis of a standard 110nm CMOS production process with some modifications needed to meet the project requirements. High resistivity n-type silicon substrates have been chosen for the sensor active volume and a n-type epitaxial layer has been included at the sensor frontside to delay the onset of the punch-through current flowing between the frontside and backside p-type implants. The sensor n-type collection electrodes are surrounded by pwells, which can host the embedded analog and digital frontend electronics, and deep pwells have been included below the pwells to shield them from the sensor substrate. Three engineering runs have been submitted and the produced wafers have been delivered in 2021, 2022 and 2023, respectively. An additional p-type implant has been added in the third production run to create an embedded gain layer below the n-type collection electrodes, to enhance the signal through avalanche multiplication. A selection of the main results obtained from the TCAD simulations and of the most relevant measurements performed on the designed MAPS passive test structures will be presented and discussed in chapter 4. In an analogous way, the experimental results obtained from the characterization of an active sensor designed for brachytherapy, called COBRA, are reported in chapter 5. The calibration of the capacitance included in the internal charge injection circuit of two TJ-Monopix2 MAPS having different substrate types is reported in chapter 6. These sensors represent examples of fully functional and full scale monolithic prototypes realized in a 180nm Tower-Jazz CMOS process, that have been characterized using X-rays fluorescence techniques at the SiLab of the University of Bonn. Finally, in the Conclusions section the main results of the research activity are summarized and the possible future spin-offs of the project are presented.

Energy efficiency is a key challenge to build a sustainable society. It can be declined in variety of ways: for instance, from the reduction of the environmental impact of appliances manufacturing, to the implementation of low-energy communication networks, or the management of the existing infrastructures in a smarter way. The actual direction is the integration of different energy systems with a common management scheme with the aim of harmonizing and integrating different energy systems. In this context, smart cities already envision the use of information communication technologies (ICT) to smartify objects and services, connecting people and machines. An important enabling technology for smart cities is certainly the Internet of Things (IoT). Both smart cities and IoT have been extensively investigated over the last few years, under the influence of European funded projects as well. Smart cities apply communication and networking technologies, very often using the paradigm of IoT, to address relevant issues like traffic congestion, population growth, crowding, and others, besides implementing innovative services, modernizing existing infrastructures, e.g. smart mobility. IoT greatly helps in monitoring and better managing energy consumption as well, realizing smart homes, smart buildings and smart grids. For what concern the power grid, in fact, the direction is to harness IoT technologies to improve flexibility, easiness of use and, ultimately, energy efficiency while preserving stability and safety. Today the electrical grid is facing deep changes, mostly caused by the intensive deployment of Distributed Energy Resources (DER) based on renewable sources such as photovoltaic plants or wind farms. Managing such heterogeneous active distribution networks (ADNs), represent one of the most important challenges to be faced in the future of energy systems. The integration of active elements into the grid is challenging because of both the great potential they bring in energy production and the hazard they may represent if not properly managed (e.g. violation of operational constraints). ADN implementation relies on the deployment of high-performance real-time monitoring and control systems. It is well accepted that the phasor measurement units (PMU) are one of the most promising instruments to overcome many problems in ADN management, as they support a number of applications, such as grid state estimation, topology detection, volt-var optimization and reverse power flow management. However, classic PMUs are conceived to measure synchrophasor in transmission systems, while the distribution ones have very different characteristics and, in general, different needs. Therefore, tailoring the characteristics of the new-generation PMUs to the needs of the ADNs is currently very important. This new kind of PMU must address few important design challenges: 1. improved angle measurement capabilities, to cope with the smaller angle differences that distribution grids exhibit; 2. low cost, to promote an extensive deployment in the grid. These two requirements are clearly in opposition. In this dissertation, a low-cost PMU design approach, partially influenced by IoT ideas, is presented.

In the era in which the robots have started to live and work everywhere and in close contact with humans, they should accurately know their own location at any time to be able to move and perform safely. In particular, large and crowded indoor environments are challenging scenarios for robots' accurate and robust localization. The theory and the results presented in this dissertation intend to address the crucial issue of wheeled robots indoor localization by proposing some novel solutions in three complementary ways, i.e. improving robots self-localization through data fusion, adopting collaborative localization (e.g. using the position information from other robots) and finally optimizing the placement of landmarks in the environment once the detection range of the chosen sensors is known. As far as the first subject is concerned, a robot should be able to localize itself in a given reference frame. This problem is studied in detail to achieve a proper and affordable technique for self-localization, regardless of specific environmental features. The proposed solution relies on the integration of relative and absolute position measurements. The former are based on odometry and on an inertial measurement unit. The absolute position and heading data instead are measured sporadically anytime some landmark spread in the environment is detected. Due to the event-based nature of such measurement data, the robot can work autonomously most of time, even if accuracy degrades. Of course, in order to keep positioning uncertainty bounded, it is important that absolute and relative position data are fused properly. For this reason, four different techniques are analyzed and compared in the dissertation. Once the local kinematic state of each robot is estimated, a group of them moving in the same environment and able to detect and communicate with one another can also collaborate to share their position information to refine self-localization results. In the dissertation, it will be shown that this approach can provide some benefits, although performances strongly depend on the metrological features of the adopted sensors as well as on the communication range. Finally, as far as the problem optimal landmark placement is concerned, this is addressed by suggesting a novel and easy-to-use geometrical criterion to maximize the distance between the landmarks deployed over a triangular lattice grid, while ensuring that the absolute position measurement sensors can always detect at least one landmark.

Gamma-ray and Fluorescence Lifetime Spectroscopies are driving the development of non-imaging silicon photon sensors and, in this context, Silicon Photo-Multipliers (SiPM)s are leading the starring role. They are 2D array of optical diodes called Single Photon Avalanche Diodes (SPAD)s, and are normally fabricated with a dedicated silicon process. SPADs amplify the charge produced by the single absorbed photon in a way that recalls the avalanche amplification exploited in Photo-Multiplier Tubes (PMT)s. Recently 2D arrays of SPADs have been realized also in standard CMOS technology, paving the way to the realization of completely custom sensors that can host ancillary electronic and digital logic on-chip. The designs of scientific apparatus have been influenced for years by the bulky PMT-based detectors. An overwhelming interest in both SiPMs and CMOS SPADs lies in the possibility of displacing these small sensors realizing new detectors geometries. This thesis examines the potential deployment of SiPM-based detector in an apparatus built for the study of the Time-Of-Flight (TOF) of Positronium (Ps) and the displacement of 2D array of CMOS SPADs in a lab-on-chip apparatus for Fluorescence Lifetime Spectroscopy. The two design procedures are performed using Monte-Carlo simulations. Characterizations of the two sensor have been carried out, allowing for a performance evaluation and a validation of the two design procedures.

3D Si radiation sensors came along with extreme radiation hard properties, primarily owing to the geometrical advantages over planar sensors where electrodes are formed penetrating through the active substrate volume. Among them: reduction of the inter-electrode distance, lower depletion voltage requirement, inter-columnar high electric field distribution, lower trapping probability, faster charge collection capability, lower power dissipation, and lower inter-pitch charge sharing. Since several years, FBK has developed 3D sensors with a double-sided technology, that have also been installed in the ATLAS Insertable B-Layer at LHC. However, the future High-Luminosity LHC (HL-LHC) upgrades, aimed to be operational by 2024, impose a complete swap of current 3D detectors with more radiation hard sensor design, able to withstand very large particle fluences up to 2×1016 cm-2 1-MeV equivalent neutrons. The extreme luminosity conditions and related issues in occupancy and radiation hardness lead to very dense pixel granularity (50×50 or 25×100 μm2), thinner active region (~100 μm), narrower columnar electrodes (~5μm diameter) with reduced inter-electrode spacing (~30 μm), and very slim edges (~100 μm) into the 3D pixel sensor design. This thesis includes the development of this new generation of small-pitch and thin 3D radiation sensors aimed at the foreseen Inner Tracker (ITk) upgrades at HL-LHC.