ABSTRACT In this work the recrystallisation of low-pressure chemical vapour-deposited amorphous s... more ABSTRACT In this work the recrystallisation of low-pressure chemical vapour-deposited amorphous silicon films on glass substrates is investigated as a function of the annealing conditions. Two different recrystallisation setups are used: either large-area excimer laser recrystallisation or conventional furnace followed by an rapid thermal treatment at 800-900 degreesC. For excimer laser annealing, an optimum in energy density is obtained, slightly greater than 550 mJ/cm(2). Further increase in the grain size and crystalline quality is obtained by repeated irradiation. In this case an energy density of 630 mJ/cm(2) gives the best results. Good correlation exists between the electrical results and the structural data. For the rapid thermal annealing, preliminary results indicate that the structural and electrical quality of the already thermally recrystallised silicon layers can be further improved by the annealing. A saturation of the improvement seems to exist with the annealing time and for a temperature of 900 degreesC, the layers are strongly degraded for times above 2 minutes.
ABSTRACT Starting with a hydrated tin dioxide powder of 3nm size obtained by the sol-gel method, ... more ABSTRACT Starting with a hydrated tin dioxide powder of 3nm size obtained by the sol-gel method, the effects of thermal treatments and grinding on the final structural properties of the nanoparticles have been investigated. It is observed that two regions with different structural properties can be distinguished in the range of temperatures between 250 and 1000 degrees C. In spire of their large grain size (>15nm), above 350-450 degrees C, these nanocrystals can be used as precursor powders for gas sensors because of their higher stability. Grinding of the starting material before calcination will be proved as a suitable method to obtain the same type of stability with lower grain size.
ABSTRACT Starting with a hydrated tin dioxide powder of 3nm size obtained by the sol-gel method, ... more ABSTRACT Starting with a hydrated tin dioxide powder of 3nm size obtained by the sol-gel method, the effects of thermal treatments and grinding on the final structural properties of the nanoparticles have been investigated. It is observed that two regions with different structural properties can be distinguished in the range of temperatures between 250 and 1000 degrees C. In spire of their large grain size (>15nm), above 350-450 degrees C, these nanocrystals can be used as precursor powders for gas sensors because of their higher stability. Grinding of the starting material before calcination will be proved as a suitable method to obtain the same type of stability with lower grain size.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012
ABSTRACT It is well known that avalanche photodiodes operated in the Geiger mode above the breakd... more ABSTRACT It is well known that avalanche photodiodes operated in the Geiger mode above the breakdown voltage offer a virtually infinite gain and time accuracy in the picosecond range that can be used for single photon detection. However, their performance in particle detection still remains unexplored. In this contribution, we are going to expose different steps that we have taken in order to prove the efficiency of the Geiger mode avalanche photodiodes in the aforementioned field. In particular, we will present a setup for the characterization of these sensors in a test beam. The expected results of the test beam at DESY and CERN have been simulated with Geant4 and will also be exposed.
A Dual Beam FIB has been used to deposit platinum contacts on nanomaterials using both electron-a... more A Dual Beam FIB has been used to deposit platinum contacts on nanomaterials using both electron-and ion-assisted deposition. Characterization of deposited platinum has been performed, and the feasibility of using these nanocontacts to extract electrical parameters of materials demonstrated. The advantage of combining electron-and ion-assisted deposition is discussed.
ABSTRACT In this work the recrystallisation of low-pressure chemical vapour-deposited amorphous s... more ABSTRACT In this work the recrystallisation of low-pressure chemical vapour-deposited amorphous silicon films on glass substrates is investigated as a function of the annealing conditions. Two different recrystallisation setups are used: either large-area excimer laser recrystallisation or conventional furnace followed by an rapid thermal treatment at 800-900 degreesC. For excimer laser annealing, an optimum in energy density is obtained, slightly greater than 550 mJ/cm(2). Further increase in the grain size and crystalline quality is obtained by repeated irradiation. In this case an energy density of 630 mJ/cm(2) gives the best results. Good correlation exists between the electrical results and the structural data. For the rapid thermal annealing, preliminary results indicate that the structural and electrical quality of the already thermally recrystallised silicon layers can be further improved by the annealing. A saturation of the improvement seems to exist with the annealing time and for a temperature of 900 degreesC, the layers are strongly degraded for times above 2 minutes.
GaAs layers grown on (001) Si by ALMBE have been investigated by conventional and high-resolution... more GaAs layers grown on (001) Si by ALMBE have been investigated by conventional and high-resolution TEM. At these interfaces Lomer dislocations have been found to predominate (6:1) in comparison to the 60° ones and are not regularly spaced (spacing variation can be as large at 4 nm), owing probably to the presence of other defects. Their atomic structures, as well
Conference on Electron Devices, 2005 Spanish, 2005
Microcoils integrated with standard CMOS technology show an increasing interest in biosensor appl... more Microcoils integrated with standard CMOS technology show an increasing interest in biosensor applications, as they allow very high sensitivity and selectivity. Simulations of the electromagnetic behaviour of the microcoils suggest the way for optimizing their properties. The sensitivity can be improved essentially by decreasing the external radius of the device, and the inductance variation increases with the number of rings, so the optimum configuration corresponds to a small coil with the highest number of rings. Focused ion beam (FIB) shows optimal capabilities to achieve these design rules, as it is a very versatile and precise direct-write technique. In this work, the fabrication process of reduced-size coils using FIB is described, as well as their preliminary characterization, showing the ability of this technique for achieving optimized sensing devices.
Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications VII, 2013
ABSTRACT Advances in SPAD arrays propose improving the fill factor by confining several SPADs in ... more ABSTRACT Advances in SPAD arrays propose improving the fill factor by confining several SPADs in the same well, with a main issue related to crosstalk. For measurements triggered only in well-defined time periods that can be known in advance, the pixels can be inhibited before the arrival of the crosstalk charge. This paper reports the crosstalk characterization of in an array of SPADs fabricated in a conventional CMOS technology in the same n-well (fill factor 67%). A long gating time gives a crosstalk not less than 2.75%, while reducing it below 2.5 ns completely eliminates crosstalk, as predicted by the theory and by TCAD simulations.
Conference on Electron Devices, 2005 Spanish, 2005
Nanowires (NWs) and nanoparticles (NPs) of different materials have been grown using either a pol... more Nanowires (NWs) and nanoparticles (NPs) of different materials have been grown using either a polycarbonate porous membrane or mesoporous silica as template. The NWs have lengths between 1 and 20 microns; their diameter, as well as the dimensions of the NPs, are in the range of a few hundreds of nanometers. In order to test their electrical characteristics, some of these NWs and NPs have been electrically contacted by using submicrometer sized metallic Pt stripes deposited using an electron and/or ion beam in a focused ion beam (FIB) system. The preliminary results show that the method used is well suited for fabrication of contacts to NWs and NPs, whose electrical behaviour can be easily evaluated. These nanocontacts could help to design future nanodevices.
Detectors and Imaging Devices: Infrared, Focal Plane, Single Photon, 2010
ABSTRACT In the last years the fabrication of SPAD cameras has become one of the main fields of i... more ABSTRACT In the last years the fabrication of SPAD cameras has become one of the main fields of interest in 3-D imaging and bioapplications. In this paper we present the comparison between two standard CMOS technologies to fabricate SPADs cameras. The two technologies used in the comparison are a high voltage 0.35mum technology from AMS and a high integration 130nm technology from STM. The advantage of using a standard CMOS technology among a dedicated is the possibility of integrating the control/reading electronics into the same die. Neither of the processes is optimized for optical applications, and no post-processing has been applied to improve the features. The technologies have been selected due to the different integration density, and different intrinsic process parameters with similar cost. Comparison has been done by fabricating several structures in both technologies which allow analyzing sensibility, noise, and time response. Experimental results show that the high voltage technology has a lower level of dark counts than the 130nm. Instead, the high integration technology has a shorter quenching time, 1.5ns, which reduces the afterpulsing events to a negligible level. In optical applications it is important to have a high integration of the camera reducing the pitch of the pixel, while noise effects can be corrected in post-processing. For low frequency events, such as high energetic particle tracking, the noise frequency has to be lower, but it is also required a high fill factor. Depending on the specific application this analysis allows to opt for the most suitable technology.
This work presents low noise readout circuits for silicon pixel detectors based on Geiger mode av... more This work presents low noise readout circuits for silicon pixel detectors based on Geiger mode avalanche photodiodes. Geiger mode avalanche photodiodes offer a high intrinsic gain as well as an excellent timing accuracy. In addition, they can be compatible with standard CMOS technologies. However, they suffer from a high intrinsic noise, which induces false counts indistinguishable from real events and represents an increase of the readout electronics area to store the false counts. We have developed new front-end electronic circuitry for Geiger mode avalanche photodiodes in a conventional 0.35 µm HV-CMOS technology based on a gated mode of operation that allows low noise operation. The performance of the pixel detector is triggered and
ABSTRACT In this work the recrystallisation of low-pressure chemical vapour-deposited amorphous s... more ABSTRACT In this work the recrystallisation of low-pressure chemical vapour-deposited amorphous silicon films on glass substrates is investigated as a function of the annealing conditions. Two different recrystallisation setups are used: either large-area excimer laser recrystallisation or conventional furnace followed by an rapid thermal treatment at 800-900 degreesC. For excimer laser annealing, an optimum in energy density is obtained, slightly greater than 550 mJ/cm(2). Further increase in the grain size and crystalline quality is obtained by repeated irradiation. In this case an energy density of 630 mJ/cm(2) gives the best results. Good correlation exists between the electrical results and the structural data. For the rapid thermal annealing, preliminary results indicate that the structural and electrical quality of the already thermally recrystallised silicon layers can be further improved by the annealing. A saturation of the improvement seems to exist with the annealing time and for a temperature of 900 degreesC, the layers are strongly degraded for times above 2 minutes.
ABSTRACT Starting with a hydrated tin dioxide powder of 3nm size obtained by the sol-gel method, ... more ABSTRACT Starting with a hydrated tin dioxide powder of 3nm size obtained by the sol-gel method, the effects of thermal treatments and grinding on the final structural properties of the nanoparticles have been investigated. It is observed that two regions with different structural properties can be distinguished in the range of temperatures between 250 and 1000 degrees C. In spire of their large grain size (>15nm), above 350-450 degrees C, these nanocrystals can be used as precursor powders for gas sensors because of their higher stability. Grinding of the starting material before calcination will be proved as a suitable method to obtain the same type of stability with lower grain size.
ABSTRACT Starting with a hydrated tin dioxide powder of 3nm size obtained by the sol-gel method, ... more ABSTRACT Starting with a hydrated tin dioxide powder of 3nm size obtained by the sol-gel method, the effects of thermal treatments and grinding on the final structural properties of the nanoparticles have been investigated. It is observed that two regions with different structural properties can be distinguished in the range of temperatures between 250 and 1000 degrees C. In spire of their large grain size (>15nm), above 350-450 degrees C, these nanocrystals can be used as precursor powders for gas sensors because of their higher stability. Grinding of the starting material before calcination will be proved as a suitable method to obtain the same type of stability with lower grain size.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012
ABSTRACT It is well known that avalanche photodiodes operated in the Geiger mode above the breakd... more ABSTRACT It is well known that avalanche photodiodes operated in the Geiger mode above the breakdown voltage offer a virtually infinite gain and time accuracy in the picosecond range that can be used for single photon detection. However, their performance in particle detection still remains unexplored. In this contribution, we are going to expose different steps that we have taken in order to prove the efficiency of the Geiger mode avalanche photodiodes in the aforementioned field. In particular, we will present a setup for the characterization of these sensors in a test beam. The expected results of the test beam at DESY and CERN have been simulated with Geant4 and will also be exposed.
A Dual Beam FIB has been used to deposit platinum contacts on nanomaterials using both electron-a... more A Dual Beam FIB has been used to deposit platinum contacts on nanomaterials using both electron-and ion-assisted deposition. Characterization of deposited platinum has been performed, and the feasibility of using these nanocontacts to extract electrical parameters of materials demonstrated. The advantage of combining electron-and ion-assisted deposition is discussed.
ABSTRACT In this work the recrystallisation of low-pressure chemical vapour-deposited amorphous s... more ABSTRACT In this work the recrystallisation of low-pressure chemical vapour-deposited amorphous silicon films on glass substrates is investigated as a function of the annealing conditions. Two different recrystallisation setups are used: either large-area excimer laser recrystallisation or conventional furnace followed by an rapid thermal treatment at 800-900 degreesC. For excimer laser annealing, an optimum in energy density is obtained, slightly greater than 550 mJ/cm(2). Further increase in the grain size and crystalline quality is obtained by repeated irradiation. In this case an energy density of 630 mJ/cm(2) gives the best results. Good correlation exists between the electrical results and the structural data. For the rapid thermal annealing, preliminary results indicate that the structural and electrical quality of the already thermally recrystallised silicon layers can be further improved by the annealing. A saturation of the improvement seems to exist with the annealing time and for a temperature of 900 degreesC, the layers are strongly degraded for times above 2 minutes.
GaAs layers grown on (001) Si by ALMBE have been investigated by conventional and high-resolution... more GaAs layers grown on (001) Si by ALMBE have been investigated by conventional and high-resolution TEM. At these interfaces Lomer dislocations have been found to predominate (6:1) in comparison to the 60° ones and are not regularly spaced (spacing variation can be as large at 4 nm), owing probably to the presence of other defects. Their atomic structures, as well
Conference on Electron Devices, 2005 Spanish, 2005
Microcoils integrated with standard CMOS technology show an increasing interest in biosensor appl... more Microcoils integrated with standard CMOS technology show an increasing interest in biosensor applications, as they allow very high sensitivity and selectivity. Simulations of the electromagnetic behaviour of the microcoils suggest the way for optimizing their properties. The sensitivity can be improved essentially by decreasing the external radius of the device, and the inductance variation increases with the number of rings, so the optimum configuration corresponds to a small coil with the highest number of rings. Focused ion beam (FIB) shows optimal capabilities to achieve these design rules, as it is a very versatile and precise direct-write technique. In this work, the fabrication process of reduced-size coils using FIB is described, as well as their preliminary characterization, showing the ability of this technique for achieving optimized sensing devices.
Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications VII, 2013
ABSTRACT Advances in SPAD arrays propose improving the fill factor by confining several SPADs in ... more ABSTRACT Advances in SPAD arrays propose improving the fill factor by confining several SPADs in the same well, with a main issue related to crosstalk. For measurements triggered only in well-defined time periods that can be known in advance, the pixels can be inhibited before the arrival of the crosstalk charge. This paper reports the crosstalk characterization of in an array of SPADs fabricated in a conventional CMOS technology in the same n-well (fill factor 67%). A long gating time gives a crosstalk not less than 2.75%, while reducing it below 2.5 ns completely eliminates crosstalk, as predicted by the theory and by TCAD simulations.
Conference on Electron Devices, 2005 Spanish, 2005
Nanowires (NWs) and nanoparticles (NPs) of different materials have been grown using either a pol... more Nanowires (NWs) and nanoparticles (NPs) of different materials have been grown using either a polycarbonate porous membrane or mesoporous silica as template. The NWs have lengths between 1 and 20 microns; their diameter, as well as the dimensions of the NPs, are in the range of a few hundreds of nanometers. In order to test their electrical characteristics, some of these NWs and NPs have been electrically contacted by using submicrometer sized metallic Pt stripes deposited using an electron and/or ion beam in a focused ion beam (FIB) system. The preliminary results show that the method used is well suited for fabrication of contacts to NWs and NPs, whose electrical behaviour can be easily evaluated. These nanocontacts could help to design future nanodevices.
Detectors and Imaging Devices: Infrared, Focal Plane, Single Photon, 2010
ABSTRACT In the last years the fabrication of SPAD cameras has become one of the main fields of i... more ABSTRACT In the last years the fabrication of SPAD cameras has become one of the main fields of interest in 3-D imaging and bioapplications. In this paper we present the comparison between two standard CMOS technologies to fabricate SPADs cameras. The two technologies used in the comparison are a high voltage 0.35mum technology from AMS and a high integration 130nm technology from STM. The advantage of using a standard CMOS technology among a dedicated is the possibility of integrating the control/reading electronics into the same die. Neither of the processes is optimized for optical applications, and no post-processing has been applied to improve the features. The technologies have been selected due to the different integration density, and different intrinsic process parameters with similar cost. Comparison has been done by fabricating several structures in both technologies which allow analyzing sensibility, noise, and time response. Experimental results show that the high voltage technology has a lower level of dark counts than the 130nm. Instead, the high integration technology has a shorter quenching time, 1.5ns, which reduces the afterpulsing events to a negligible level. In optical applications it is important to have a high integration of the camera reducing the pitch of the pixel, while noise effects can be corrected in post-processing. For low frequency events, such as high energetic particle tracking, the noise frequency has to be lower, but it is also required a high fill factor. Depending on the specific application this analysis allows to opt for the most suitable technology.
This work presents low noise readout circuits for silicon pixel detectors based on Geiger mode av... more This work presents low noise readout circuits for silicon pixel detectors based on Geiger mode avalanche photodiodes. Geiger mode avalanche photodiodes offer a high intrinsic gain as well as an excellent timing accuracy. In addition, they can be compatible with standard CMOS technologies. However, they suffer from a high intrinsic noise, which induces false counts indistinguishable from real events and represents an increase of the readout electronics area to store the false counts. We have developed new front-end electronic circuitry for Geiger mode avalanche photodiodes in a conventional 0.35 µm HV-CMOS technology based on a gated mode of operation that allows low noise operation. The performance of the pixel detector is triggered and
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Papers by Anna Vila