Radiation Hardness Properties Research Articles

Ni/Ga2O3 based Schottky diode temperature sensor

Temperature sensors are the integrated part of electronics used in most of the applications. Present work demonstrates the temperature sensor based on ultra-wide bandgap semiconducting material, i.e.,Ga2O3. The material is known for its wider bandgap and radiation hardness properties. Ni/Ga2O3 based Schottky barrier device is simulated for sensing the temperature in the current range of 100 µA to 0.1 µA and in temperature range from 200 K to 600 K using SILVACO Atlas software. Relevant models such as bandgap narrowing, Schokely-Read-Hall, etc. were employed to ensure accuracy in the results. The simulated current–voltage (I-V) plots showed exponential variation and followed ideal thermionic emission model. The I-V plots were used to find the thermal sensitivity of device under considerations, which showed linearity in the measured current range. The maximum sensitivity is estimated as 3.22 mV/K at measuring current level of 0.1 µA.

Performance of neutron-irradiated 4H-silicon carbide diodes subjected to alpha radiation

The unique electrical and material properties of 4H-silicon-carbide (4H-SiC) make it a promising candidate material for high rate particle detectors. In contrast to the ubiquitously used silicon (Si), 4H-SiC offers a higher carrier saturation velocity and larger breakdown voltage, enabling a high intrinsic time resolution and mitigating pile-up effects. Additionally, as radiation hardness requirements grow more demanding in the context of future high luminosity high energy physics experiments, wide-bandgap materials such as 4H-SiC could offer better performance due to low dark currents and higher atomic displacement thresholds. In this work, the detector performance of 50 µm thick 4H-SiC p-in-n planar pad sensors was investigated at room temperature, using an 241Am alpha source at reverse biases of up to 1100 V. Samples subjected to neutron irradiation with fluences of up to 1 × 1016 neq/cm2 were included in the study in order to quantify the radiation hardness properties of 4H-SiC. A calibration of the absolute number of collected charges was performed using a GATE simulation. The obtained results are compared to previously performed UV transient current technique (TCT) studies. Samples exhibit a drop in charge collection efficiency (CCE) with increasing irradiation fluence, partially compensated at high reverse bias voltages far above full depletion voltage. At fluences of 5 × 1014 neq/cm2 and 1 × 1015 neq/cm2, CCEs of 64 % and 51 % are obtained, decreasing to 15 % at 5 × 1015 neq/cm2. A plateau of the collected charges is observed in accordance with the depletion of the volume the alpha particles penetrate for an unirradiated reference detector. For the neutron-irradiated samples, such a plateau only becomes apparent at higher reverse bias, roughly 600 V and 900 V for neutron fluences of 5 × 1014 neq/cm2 and 1 × 1015 neq/cm2. For the highest investigated fluence, CCE behaves almost linearly with increasing reverse bias. Compared to UV-TCT measurements, the reverse bias required to deplete a sensitive volume covering full energy deposition is lower, due to the small penetration depth of the alpha particles. At the highest reverse bias, the measured CCE values agree well with earlier UV-TCT studies, with discrepancies between 1% and 5%.

The influence of CeF3 on radiation hardness and luminescence properties of Gd2O3–B2O3 glass scintillator

The effect of CeF3 concentration and γ-irradiation on the physical, optical and luminescence properties of Gd2O3–B2O3–CeF3 glasses were studied in this work. Before irradiation, the addition of CeF3 in glass degraded the network connectivity observed from FTIR and possibly created the non-bridging oxygen (NBO) in glass structure. This NBO caused the reduction of Ce3+/Ce4+ ratio in XANES, the red-shift in transmission spectra and the raise of refractive index with addition of CeF3 content. Such red-shift also was influenced by 4f–5d transition of Ce3+ dopant. This ion generated the strongest photoluminescence (PL) and radioluminescence (RL) in 0.3 mol% CeF3-doped glass with nanoseconds decay time. The irradiation with γ-rays damaged the glass structure, broke the chemical bonds, and created color center in the glass network. The non-bridging oxygen hole center (NBOHC), that absorbed photons in the visible light region, caused the darkening, color change and increment of refractive index. These irradiation effects on glass were mitigated by the addition of CeF3 that the electron donation of Ce3+ decreased the number of NBOHC. The Ce3+/Ce4+ ratio in most glasses after irradiation then reduced compared to them before irradiation, resulting to the decrease in PL and RL intensity. Our results confirm that CeF3 can enhance the radiation hardness of glass and the 0.3 mol% CeF3-doped glass is a promising glass scintillator.

Fabrication of a Hydrogenated Amorphous Silicon Detector in 3-D Geometry and Preliminary Test on Planar Prototypes

Hydrogenated amorphous silicon (a-Si:H) can be produced by plasma-enhanced chemical vapor deposition (PECVD) of SiH4 (silane) mixed with hydrogen. The resulting material shows outstanding radiation hardness properties and can be deposited on a wide variety of substrates. Devices employing a-Si:H technologies have been used to detect many different kinds of radiation, namely, minimum ionizing particles (MIPs), X-rays, neutrons, and ions, as well as low-energy protons and alphas. However, the detection of MIPs using planar a-Si:H diodes has proven difficult due to their unsatisfactory S/N ratio arising from a combination of high leakage current, high capacitance, and limited charge collection efficiency (50% at best for a 30 µm planar diode). To overcome these limitations, the 3D-SiAm collaboration proposes employing a 3D detector geometry. The use of vertical electrodes allows for a small collection distance to be maintained while preserving a large detector thickness for charge generation. The depletion voltage in this configuration can be kept below 400 V with a consequent reduction in the leakage current. In this paper, following a detailed description of the fabrication process, the results of the tests performed on the planar p-i-n structures made with ion implantation of the dopants and with carrier selective contacts are illustrated.

Evaluating the Radiation Effects on the Characteristics of the Silicon Avalanche Photodiode with Protons

Silicon avalanche photodiode (Si APD) plays important roles in high sensitive optical detecting applications, such as remote sensing, radiation detection and optical communication etc. However, in the space, the Si APD would unavoidably suffer radiation damage, which would degrade the Si APD performance, like dark current, responsivity and gain etc. Here, we report the results of Si APD radiation tests with protons to evaluate their radiation hardness properties and suitability for space missions. With this motivation, samples have been radiated using 50 MeV protons with maximum does 1E12 p(proton)/cm2 The test results show that the Si APD dark current increment is negligible when the radiation dose is below 1E11 p/cm2, ∼10 nA, satisfying most nanowatt level detecting applications. As the radiation dose further increases to 1E12 p/cm2, the Si APD breakdown voltage has a measureable decrement, which subsequently increases the dark current and gain. And through over two years’ in-orbit test, the Si APD dark current keeps below 1 nA, while the responsively is ∼4.9 A/W.

Development of a technology for the fabrication of Low-Gain Avalanche Diodes at BNL

Low-Gain Avalanche Detectors are gathering interest in the High-Energy Physics community thanks to their fast-timing and radiation-hardness properties, which are planned to be exploited, for example, in timing detectors for the upgrades of the ATLAS and CMS detectors at the High Luminosity LHC. This new technology has also raised interest for its possible application for photon detection in medical physics, imaging and photon science. The main characteristic of this type of device is a thin and highly-doped layer that provides internal and moderate gain, in the order of 10-20, that enhances the signal amplitude. Furthermore, the thin substrate of a few tens of microns allows fast carrier collection. This paper details on the fabrication technology, specifically developed at Brookhaven National Laboratory for the detection of minimum ionizing particles. The static electrical characterization and the gain measurements on prototypes will be reported, too.

A large area diamond-based beam tagging hodoscope for ion therapy monitoring

The MoniDiam project is part of the French national collaboration CLaRyS (Contrôle en Ligne de l’hAdronthérapie par RaYonnements Secondaires) for on-line monitoring of hadron therapy. It relies on the imaging of nuclear reaction products that is related to the ion range. The goal here is to provide large area beam detectors with a high detection efficiency for carbon or proton beams giving time and position measurement at 100 MHz count rates (beam tagging hodoscope). High radiation hardness and intrinsic electronic properties make diamonds reliable and very fast detectors with a good signal to noise ratio. Commercial Chemical Vapor Deposited (CVD) poly-crystalline, heteroepitaxial and monocrystalline diamonds were studied. Their applicability as a particle detector was investigated using α and β radioactive sources, 95 MeV/u carbon ion beams at GANIL and 8.5 keV X-ray photon bunches from ESRF. This facility offers the unique capability of providing a focused (~1 μm) beam in bunches of 100 ps duration, with an almost uniform energy deposition in the irradiated detector volume, therefore mimicking the interaction of single ions. A signal rise time resolution ranging from 20 to 90 ps rms and an energy resolution of 7 to 9% were measured using diamonds with aluminum disk shaped surface metallization. This enabled us to conclude that polycrystalline CVD diamond detectors are good candidates for our beam tagging hodoscope development. Recently, double-side stripped metallized diamonds were tested using the XBIC (X Rays Beam Induced Current) set-up of the ID21 beamline at ESRF which permits us to evaluate the capability of diamond to be used as position sensitive detector. The final detector will consist in a mosaic arrangement of double-side stripped diamond sensors read out by a dedicated fast-integrated electronics of several hundreds of channels.

Study of gain homogeneity and radiation effects of Low Gain Avalanche Pad Detectors

Silicon detectors with intrinsic charge amplification implementing a n++-p+-p structure are considered as a sensor technology for future tracking and timing applications in high energy physics experiments. The performance of the intrinsic gain in Low Gain Avalanche Detectors (LGAD) after irradiation is crucial for the characterization of radiation hardness and timing properties in this technology. LGAD devices irradiated with reactor neutrons or 800 MeV protons reaching fluences of 2.3×1016neq/cm2 were characterized using Transient Current Technique (TCT) measurements with red and infra-red laser pulses. Leakage current variations observed in different production lots and within wafers were investigated using Thermally Stimulated Current (TSC). Results showed that the intrinsic charge amplification is reduced with increasing fluence up to 1015neq/cm2 which is related to an effective acceptor removal. Further relevant issues were charge collection homogeneity across the detector surface and leakage current performance before and after irradiation.

Optical properties and radiation hardness of Pr-doped sol-gel silica: Influence of fiber drawing process

The optical emission from the 5d – 4f allowed transition of Pr3+ ions embedded in sol-gel silica is investigated for High Energy Physics applications requiring fast scintillating materials.A complete and detailed characterization of the optical, scintillation and radiation hardness properties of Pr-doped silica is carried out employing different experimental techniques including steady-state and time-resolved photo-luminescence, radio- and thermo-luminescence, scintillation and optical absorption.Optical absorption measurements, performed after X-ray irradiation sequences up to 1kGy, evidence the formation of radiation-induced absorption bands related to point defects acting as color centers. Spontaneous partial recovery of the radiation-induced defects at room temperature, as well as after thermal treatments, is also disclosed.Particular attention is paid to the comparison between bulk silica, both before and after a melting process, and fibers. The results reveal the presence of a lower concentration of optically active defects in melted glass. Such comparison highlights a role of the fiber drawing in modifying the glass defectiveness, consisting in the occurrence of a structural reorganization of the amorphous network during the process.

RADIATION PERFORMANCE OF GAN AND INAS/GAAS QUANTUM DOT BASED DEVICES SUBJECTED TO NEUTRON RADIATION

In addition to their useful optoelectronics functions, gallium nitride (GaN) and quantum dots (QDs) based structures are also known for their radiation hardness properties. With demands on such semiconductor material structures, it is important to investigate the differences in reliability and radiation hardness properties of these two devices. For this purpose, three sets of GaN light-emitting diode (LED) and InAs/GaAs dot-in-a well (DWELL) samples were irradiated with thermal neutron of fluence ranging from 3×1013 to 6×1014 neutron/cm2 in PUSPATI TRIGA research reactor. The radiation performances for each device were evaluated based on the current-voltage (I-V) and capacitance-voltage (C-V) electrical characterisation method. Results suggested that the GaN based sample is less susceptible to electrical changes due to the thermal neutron radiation effects compared to the QD based sample.

Studies of irradiated AMS H35 CMOS detectors for the ATLAS tracker upgrade

Silicon detectors based on the HV-CMOS technology are being investigated as possible candidate for the outer layers of the ATLAS pixel detector for the High Luminosity LHC. In this framework the H35Demo ASIC has been produced in the 350 nm AMS technology (H35). The H35Demo chip has a large area (18.49 × 24.40 mm2) and includes four different pixel matrices and three test structures. In this paper the radiation hardness properties, in particular the evolution of the depletion region with fluence is studied using edge-TCT on test structures. Measurements on the test structures from chips with different substrate resistivity are shown for non irradiated and irradiated devices up to a cumulative fluence of 2 ⋅ 1015 1 MeV neq / cm2.

Effects of quenching, irradiation, and annealing processes on the radiation hardness of silica fiber cladding materials (I)

Abstract Silica optical fiber cladding materials were experimentally treated by a series of processes. The treatments involved quenching, irradiation, followed by annealing and subsequent re-irradiation, and they were conducted in order to improve the radiation hardness. The microstructural properties of the treated materials were subsequently investigated. Following the treatment of the optical fiber cladding materials, the results from the electron spin resonance (ESR) analysis demonstrated that there was a significant decrease in the radiation-induced defect structures. The ESR signals became significantly weaker when the samples were annealed at 1000 °C in combination with re-irradiation. In addition, the microstructure changes within the silica optical fiber cladding material were also analyzed using Raman spectroscopy. The experimental results demonstrate that the Si O Si bending vibrations at ω 3 = 800–820 cm −1 and ω 4 = 1000–1200 cm −1 (with longitudinal optical (LO) and transverse optical (TO) splitting bands) were relatively unaffected by the quenching, irradiation, and annealing treatments. In particular, the annealing process resulted in the disappearance of the defect centers; however, the LO and TO modes at the ω 3 and ω 4 bands were relatively unchanged. With the additional support of the ESR test results, we can conclude that the combined treatment processes can significantly enhance the radiation hardness properties of the optical fiber cladding materials.

Gamma-ray irradiation effects on electrical properties of ferroelectric PbTiO3 and Pb(Zr0.52Ti0.48)O3 thin films

We investigated gamma-ray irradiation effects on electrical properties of ferroelectric PbTiO3 (PTO) and Pb(Zr0.52Ti0.48)O3 (PZT) thin films. PTO and PZT thin films were prepared on the Pt/Ti/SiO2/Si substrates by using a sol–gel method with a spin-coating process. The prepared PTO and PZT thin films were subjected to gamma radiation with various total doses from 0kGy to 300kGy. There were no noticeable morphological and structural changes in PTO and PZT films before and after irradiation. As a total dose increases up to 300kGy, a larger degradation behavior of electrical properties was observed in the PZT films rather than in the PTO films. About 35% of remanent polarization value decreased for the PZT films, while just 10% of that decreased for the PTO films. Dielectric constant of PZT films decreased much from 850 to 580, but that of the PTO films decreased just a little from 400 to 340. This degradation behavior of polarization and dielectric properties can be explained by the pinning of domain walls by some radiation-induced defects. These results suggest that the PTO films have higher radiation hardness properties than the PZT films.

Diamond detector for alpha-particle spectrometry

An artificially grown high purity diamond was used as a detector for alpha-particle spectrometry. Diamond detectors can match the performance of silicon detectors employed in standard continuous air monitoring systems. Its radiation hardness and electronic properties make them ideal to work under extreme condition such as high temperature and ambient lights. A 50μm thickness single-crystal diamond detector has been compared with a 300μm passivated implanted planar silicon detector, under ambient conditions.

Passivation of SiC device surfaces by aluminum oxide

A steady improvement in material quality and process technology has made electronic silicon carbide devices commercially available. Both rectifying and switched devices can today be purchased from several vendors. This successful SiC development over the last 25 years can also be utilized for other types of devices, such as light emitting and photovoltaic devices, however, there are still critical problems related to material properties and reliability that need to be addressed. This contribution will focus on surface passivation of SiC devices. This issue is of utmost importance for further development of SiC MOSFETs, which so far has been limited by reliability and low charge carrier surface mobilities. Also bipolar devices, such as BJTs, LEDs, or PV devices will benefit from more efficient and reliable surface passivation techniques in order to maintain long charge carrier lifetimes. Silicon carbide material enables the devices to operate at higher electric fields, higher temperatures and in more radiation dense applications than silicon devices. To be able to utilize the full potential of the SiC material, it is therefore necessary to develop passivation layers that can sustain these more demanding operation conditions. In this presentation it will also be shown that passivation layers of Al2O3 deposited by atomic layer deposition have shown superior radiation hardness properties compared to traditional SiO2-based passivation layers.

Building memristive and radiation hardness TiO2-based junctions

We study micro-scale TiO2 junctions that are suitable to be used as resistive random-access memory nonvolatile devices with radiation hardness memristive properties. The fabrication and structural and electrical characterization of the junctions are presented. We obtained a retentivity of 105s, an endurance of 104cycles and reliable switching with short electrical pulses (time-width below 10ns). Additionally, the devices were exposed to 25MeV oxygen ions. Then, we performed electrical measurements comparing pristine and irradiated devices in order to check the feasibility of using these junctions as memory elements with memristive and radiation hardness properties.

Radiation tests of single photon avalanche diode for space applications

Single photon avalanche diodes (SPADs) have been recently studied as photodetectors for applications in space missions. In this presentation we report the results of radiation hardness test on large area SPAD (actual results refer to SPADs having 500μm diameter). Dark counts rate as low as few kHz at −10°C has been obtained for the 500μm devices, before irradiation. We performed bulk damage and total dose radiation tests with protons and gamma-rays in order to evaluate their radiation hardness properties and their suitability for application in a Low Earth Orbit (LEO) space mission. With this aim SPAD devices have been irradiated using up to 20krad total dose with gamma-rays and 5krad with protons. The test performed show that large area SPADs are very sensitive to proton doses as low as 2×108 (1MeVeq)n/cm2 with a significant increase in dark counts rate (DCR) as well as in the manifestation of the “random telegraph signal” effect. Annealing studies at room temperature (RT) and at 80°C have been carried out, showing a high decrease of DCR after 24–48h at RT. Lower protons doses in the range 1–10×107 (1MeVeq)n/cm2 result in a lower increase of DCR suggesting that the large-area SPADs tested in this study are well suitable for application in low-inclination LEO, particularly useful for gamma-ray astrophysics.

Doping of polysiloxane rubbers for the production of organic scintillators

Polysiloxane rubbers have been produced with different concentrations of phenyl groups and of dye molecules in order to find the best synthesis conditions for reaching a high light yield. In particular, two different polymer compositions were examined, namely with 15% and 22% of phenyl units in the starting resin. 2,5-Diphenyl oxazole (PPO) as a primary dopant and Lumogen F Violet 570 as secondary dopant were dispersed in the polysiloxane. Ion beam induced luminescence (IBIL) technique was employed for studying radioluminescence and radiation hardness properties. The α and γ scintillation yields were analyzed by measuring the pulse height spectra from 241Am and 60Co radioactive sources. First tests on the suitability of these materials to the detection of fast neutrons were also performed with a TOF procedure. Preliminary results indicate that these materials exhibit a scintillation yield comparable with NE102 plastic scintillator.

Diamond X-ray beam-position monitoring using signal readout at the synchrotron radiofrequency

Single-crystal diamond is a material with great potential for the fabrication of X-ray photon beam-position monitors with submicrometre spatial resolution. Low X-ray absorption combined with radiation hardness and excellent thermal-mechanical properties make possible beam-transmissive diamond devices for monitoring synchrotron and free-electron laser X-ray beams. Tests were made using a white bending-magnet synchrotron X-ray beam at DESY to investigate the performance of a position-sensitive diamond device using radiofrequency readout electronics. The device uniformity and position response were measured in a 25 microm collimated X-ray beam with an I-Tech Libera ;Brilliance' system. This readout system was designed for position measurement and feedback control of the electron beam in the synchrotron storage ring, but, as shown here, it can also be used for accurate position readout of a quadrant-electrode single-crystal diamond sensor. The centre-of-gravity position of the F4 X-ray beam at the DORIS III synchrotron was measured with the diamond signal output digitally sampled at a rate of 130 Msample s(-1) by the Brilliance system. Narrow-band filtering and digital averaging of the position signals resulted in a measured position noise below 50 nm (r.m.s.) for a 10 Hz bandwidth.

ASTEROID: A 64 channel ASIC for source follower readout of DEPFET arrays for X-ray astronomy

The 64 channel ASTEROID ASIC has been developed to readout DEPFET Macro-Pixel Arrays operated in source follower mode. In particular ASTEROID will be coupled with the DEPFET Macro-Pixel sensors designed for the X-ray astronomy application BepiColombo. This is a satellite-based mission that requires a detector system with high speed readout, high energy resolution and radiation hardness properties. In the source follower operating mode of the DEPFETs, the front-end electronics is AC-coupled. This allows easy coping with non homogeneity of the pixel matrix and an easy compensation of threshold voltage shifts of the DEPFET devices due to radiation damage. In order to achieve the low noise value required at short processing time, ASTEROID implements a trapezoidal weighting function. This is the time-limited optimum filter for white series noise, which is dominant at the foreseen readout speed. The ASIC is realized in the 0.35 μ m 3.3 V AMS CMOS technology. The outputs of the 64 analog channels are multiplexed to one serial output with a speed up to 20 MHz. Thanks to the new multiplexer architecture adopted, ASTEROID is the only ASIC that allows window-mode readout of the pixel matrices, i.e. that allows to address selectively arbitrary sub-areas of the pixel array or even to readout different sub-areas at different speeds. In order to fully operate the 64 channels in parallel, the ASIC contains a digital section that generates the timing signals for the analog circuits. This digital section is based on SEU-immune dual port memory cells. ASTEROID has been tested for the first time with a demonstrator 64 × 64 macro-pixel Matrix of the size of 3.2 × 3.2 cm 2 . The energy resolution measured on the Mn-k α peak of 55Fe is of 124 eV with a pixel processing time of 4.8 μ s at - 80 ∘ C . This excellent result, never achieved before with source follower DEPFET at this readout speed, perfectly matches the requirements of BepiColombo Mission.