Extreme Radiation Hardness Research Articles

Exploring the Limits: Degradation Behavior of Lead Halide Perovskite Films under Exposure to Ultrahigh Doses of γ Rays of Up to 10 MGy

Herein, we show that thin films of MAPbI3, FAPbI3, (CsMA)PbI3, and (CsMAFA)PbI3, where MA and FA are methylammonium and formamidinium cations, respectively, tolerate ultrahigh doses of γ rays approaching 10 MGy without significant changes in their absorption spectra. However, among the studied materials, FAPbI3 was the only one that did not form metallic lead due to its extreme radiation hardness. Infrared near-field optical microscopy revealed the radiation-induced depletion of organic cations from the grains of MAPbI3 and their accumulation at the grain boundaries, whereas FAPbI3 on the contrary lost FA cations from the grain boundaries. The multication (CsMAFA)PbI3 perovskite underwent a facile phase segregation to domains enriched with MA and FA cations, which is a principally new radiation-induced degradation pathway. Our findings suggest that the radiation hardness of the rationally designed perovskite semiconductors could go far beyond the impressive threshold of 10 MGy we set herein for FAPbI3 films, which opens many exciting opportunities for practical implementation of these materials.

Extreme γ-ray radiation hardness and high scintillation yield in perovskite nanocrystals

Extreme γ-ray radiation hardness and high scintillation yield in perovskite nanocrystals

TCAD simulation of small-pitch 3D sensors for pixel detector upgrades at High Luminosity LHC

Applications at the High Luminosity LHC (HL-LHC) have required the development of a new generation of 3D pixel sensors with increased pixel granularity, extreme radiation hardness and low material budget. To this purpose, new 3D pixels have small pitch (e.g., 50×50 or 25×100 μm2) and reduced active thickness (∼100 μm). Owing to the small inter-electrode spacing (∼28 μm in the most aggressive designs). These 3D pixels are expected to be radiation hard even after irradiation at the hadron fluences. Indeed, they are of interest for the innermost tracking layers of ATLAS and CMS (∼2×1016 neq cm−2), and beyond. In order to estimate the charge collection efficiency (CCE) after irradiation, TCAD simulations can be conveniently used, providing useful information for the optimization of sensor design and fabrication technology. Within the AIDA-2020 project, with reference to the new single-sided 3D technology from FBK (Trento, Italy), we have simulated the CCE of pixel sensors with different inter-electrode spacing irradiated at different fluences. For these simulations, a 2D domain was used, consisting of a horizontal slice taken at half the depth of a 3D sensor. Simulations consider the hit of a minimum ionizing particle, described by the Heavy Ion model at different points within the active area. In addition, bulk radiation damage is accounted by using advanced deep-level trap models. This paper reports a comprehensive description of the simulation results based on a radiation model validated by comparison to experimental results from n-in-p strip detectors at 248 K and 900 V bias.

INFN-FBK developments of 3D sensors for High-Luminosity LHC

3D type of pixel sensors is a promising option for the innermost pixel layer at the High-Luminosity LHC. However, the required very high hit-rate capabilities, finer pixel granularity, extreme radiation hardness and reduced material budget call for a downscale of the pixel size as compared to existing 3D sensors, involving smaller pitch (e.g. 50 × 50 or 25×100μm2), shorter inter-electrode spacing (∼30μm), narrower electrodes (∼6μm diameter), and reduced active thickness (∼100–150μm). Within a joint R&D effort with INFN, FBK has produced a new generation of 3D pixel sensors with these challenging features. In this talk preliminary results from the electrical and functional characterisation of the first prototypes are reported, included their behaviour after large radiation fluence, close to the ones expected in the High Luminosity LHC environment. Prospects for the next prototypes are also presented.

Extreme radiation hard thin film CZTSSe solar cell

In this work, we have demonstrated the extreme radiation hardness of thin film CZTSSe solar cells. Thin film solar cells with CZTSSe, CZTS and CIGS absorber layers were irradiated with 3 MeV protons. No degradation in device parameters was observed until a displacement damage dose of 2 × 1010 MeV/g for CZTS and CZTSSe. CIGS solar cells degraded by 13% at the same dose. For the highest proton dose both the CZTSSe and CZTS degraded by 16% while CIGS suffered from 34% degradation in efficiency. The degradation in efficiency maybe attributed to the reduction in the minority carrier lifetime due to radiation induced lattice defects. Comparisons with previously available literature show that our CZTS technology has superior radiation hardness by about two orders of magnitude compared to existing state of the art Si and GaAs technology.

First production of new thin 3D sensors for HL-LHC at FBK

Owing to their intrinsic (geometry dependent) radiation hardness, 3D pixel sensors are promising candidates for the innermost tracking layers of the forthcoming experiment upgrades at the “Phase 2” High-Luminosity LHC (HL-LHC) . To this purpose, extreme radiation hardness up to the expected maximum fluence of 2 × 1016 neq.cm−2 must come along with several technological improvements in a new generation of 3D pixels, i.e., increased pixel granularity (50 × 50 or 25 × 100 μ m2 cell size), thinner active region (∼ 100 μm), narrower columnar electrodes (∼ 5 μm diameter) with reduced inter-electrode spacing (∼ 30 μm), and very slim edges (∼ 100 μm). The fabrication of the first batch of these new 3D sensors was recently completed at FBK on Si-Si direct wafer bonded 6” substrates. Initial electrical test results, performed at wafer level on sensors and test structures, highlighted very promising performance, in good agreement with TCAD simulations: low leakage current (< 1 pA/column), intrinsic breakdown voltage of more than 150 V, capacitance of about 50 fF/column, thus assessing the validity of the design approach. A large variety of pixel sensors compatible with both existing (e.g., ATLAS FEI4 and CMS PSI46) and future (e.g., RD53) read-out chips were fabricated, that were also electrically tested on wafer using a temporary metal layer patterned as strips shorting rows of pixels together. This allowed a statistically significant distribution of the relevant electrical quantities to be obtained, thus gaining insight into the impact of process-induced defects. A few 3D strip test structures were irradiated with X-rays, showing inter-strip resistance of at least several GΩ even after 50 Mrad(Si) dose, thus proving the p-spray robustness. We present the most important design and technological aspects, and results obtained from the initial investigations.

Charge multiplication effect in thin diamond films

Herein, we report on the enhanced sensitivity for the detection of charged particles in single crystal chemical vapour deposition (scCVD) diamond radiation detectors. The experimental results demonstrate charge multiplication in thin planar diamond membrane detectors, upon impact of 18 MeV O ions, under high electric field conditions. Avalanche multiplication is widely exploited in devices such as avalanche photo diodes, but has never before been reproducibly observed in intrinsic CVD diamond. Because enhanced sensitivity for charged particle detection is obtained for short charge drift lengths without dark counts, this effect could be further exploited in the development of sensors based on avalanche multiplication and radiation detectors with extreme radiation hardness.

CERN-RD39 collaboration activities aimed at cryogenic silicon detector application in high-luminosity Large Hadron Collider

Beam Loss Monitors (BLM) made of silicon are new devices for monitoring of radiation environment in the vicinity of superconductive magnets of the Large Hadron Collider. The challenge of BLMs is extreme radiation hardness, up to 1016 protons/cm2 while placed in superfluid helium (temperature of 1.9K). CERN BE-BI-BL group, together with CERN-RD39 collaboration, has developed prototypes of BLMs and investigated their device physics. An overview of this development—results of the in situ radiation tests of planar silicon detectors at 1.9K, performed in 2012 and 2014—is presented. Our main finding is that silicon detectors survive under irradiation to 1×1016p/cm2 at 1.9K. In order to improve charge collection, current injection into the detector sensitive region (Current Injection Detector (CID)) was tested. The results indicate that the detector signal increases while operated in CID mode.

The INFN–FBK “Phase-2” R&D program

We report on the 3-year INFN ATLAS–CMS joint research activity in collaboration with FBK, started in 2014, and aimed at the development of new thin pixel detectors for the High Luminosity LHC Phase-2 upgrades. The program is concerned with both 3D and planar active-edge pixel sensors to be made on 6” p-type wafers. The technology and the design will be optimized and qualified for extreme radiation hardness (2×1016neqcm−2). Pixel layouts compatible with present (for testing) and future (RD53 65nm) front-end chips of ATLAS and CMS are considered. The paper covers the main aspects of the research program, from the sensor design and fabrication technology, to the results of initial tests performed on the first prototypes.

Defect annealing in Mn/Fe-implanted TiO2 (rutile)

A study of the annealing processes and charge state of dilute Fe in rutile TiO2 single crystals was performed in the temperature range 143–662 K, utilizing online 57Fe emission Mössbauer spectroscopy following low concentrations (<10−3 at%) implantation of 57Mn (T1/2 = 1.5 min). Both Fe3+ and Fe2+ were detected throughout the temperature range. Three annealing stages were distinguished: (i) a broad annealing stage below room temperature leading to an increased Fe3+ fraction; (ii) a sharp annealing stage at ∼330 K characterized by conversion of Fe3+ to Fe2+ and changes in the hyperfine parameters of Fe2+, attributed to the annealing of Ti vacancies in the vicinity of the probe atoms; and (iii) an annealing stage in the temperature range from 550 to 600 K, where all Fe ions are transformed to Fe3+, attributed to the annealing of the nearby O vacancies. The dissociation energy of MnTi–VO pairs was estimated to be 1.60(15) eV. Fe2+ is found in an environment where it can probe the lattice structure through the nuclear quadrupole interaction evidencing the extreme radiation hardness of rutile TiO2. Fe3+ is found in a paramagnetic state with slow spin–lattice relaxation which follows a ∼Tn temperature dependence with 4.1 < n < 6.3 at T > 350 K.

Comparative measurements of highly irradiated n-in-p and p-in-n 3D silicon strip detectors

Silicon detectors in 3D technology are a candidate for applications in environments requiring an extreme radiation hardness, as in the innermost layers of the detectors at the proposed High-Luminosity LHC. In 3D detectors, the electrodes are made of columns etched into the silicon perpendicular to the surface. This leads to higher electric fields, a smaller depletion voltage and a reduced trapping probability of the charge carriers compared to standard planar detectors. In this article, the signal and the noise of irradiated n-in-p and p-in-n 3D silicon strip detectors are compared. The devices under test have been irradiated up to a fluence of 2×1016 1 MeV neutron equivalent particles per square centimetre (neq/cm2), which corresponds to the fluence expected for the inner pixel detector layers at the High-Luminosity LHC. A relative charge collection efficiency of approximately 70% was obtained even after the highest irradiation fluence with both detector types. The influence of different temperatures on the signal and the noise is investigated and results of annealing measurements are reported.

Silicon detectors for the sLHC

In current particle physics experiments, silicon strip detectors are widely used as part of the inner tracking layers. A foreseeable large-scale application for such detectors consists of the luminosity upgrade of the Large Hadron Collider (LHC), the super-LHC or sLHC, where silicon detectors with extreme radiation hardness are required. The mission statement of the CERN RD50 Collaboration is the development of radiation-hard semiconductor devices for very high luminosity colliders. As a consequence, the aim of the R&D programme presented in this article is to develop silicon particle detectors able to operate at sLHC conditions. Research has progressed in different areas, such as defect characterisation, defect engineering and full detector systems. Recent results from these areas will be presented. This includes in particular an improved understanding of the macroscopic changes of the effective doping concentration based on identification of the individual microscopic defects, results from irradiation with a mix of different particle types as expected for the sLHC, and the observation of charge multiplication effects in heavily irradiated detectors at very high bias voltages.

Single crystal artificial diamond detectors for VUV and soft X-rays measurements on JET thermonuclear fusion plasma

Diamond appears to be a promising material for VUV and soft X-ray radiation detection. Its wide band-gap (5.5 eV) results in a very low leakage current (it can operate above room temperature) and its electronic properties (high carrier mobility) allow a fast time response. More importantly, it is optimally suited for harsh environment applications, like those in the JET Tokamak located at the Culham laboratory (UK). Its extreme radiation hardness is well known and another interesting feature, again related to the wide band-gap, is its selective sensitivity to radiation with wavelengths shorter than 225 nm (visible-blind detectors).We report on the performances of two photodetectors based on Chemical Vapor Deposition (CVD) single crystal diamonds, one optimized for extreme UV detection, the other for soft X-ray radiation detection in the 0.8–8 keV range. These detectors have been fabricated at Roma “Tor Vergata” University using a p-type/intrinsic/metal configuration and they behave like photodiodes allowing operation with no external applied voltage. They have been installed on JET inside a vacuum chamber with a direct horizontal view of JET plasma without any wavelength selection. Their low thickness, low sensitivity to gamma ray and the unbiased operation mode make both detectors ideal for a Tokamak environment. The measurements routinely performed at JET show a low intrinsic dark current (∼0.01 pA) and very high signal to noise ratio (50 dB). Both detectors show a fast response and their signals are acquired using an electronic chain and ADC able to operate at 200 kHz, providing very interesting results for MHD and Edge Localized Modes (ELMs) instability studies on fusion plasmas.

Efficiency measurements for 3D silicon strip detectors

Silicon strip detectors are widely used as part of the inner tracking layers in particle physics experiments. For applications at the luminosity upgrade of the Large Hadron Collider (LHC), the sLHC, silicon detectors with extreme radiation hardness are required. The 3D detector design, where electrodes are processed from underneath the strips into the silicon bulk material, provides a way to enhance the radiation tolerance of standard planar silicon strip detectors. Detectors with several innovative 3D designs that constitute a simpler and more cost-effective processing than the 3D design initially proposed were connected to read-out electronics from LHC experiments and subsequently tested. Results on the amount of charge collected, the noise and the uniformity of charge collection are given.

Recent advances in the development of semiconductor detectors for SLHC

For the luminosity upgrade of the LHC, the SLHC, the tracking systems of the LHC experiments need to be replaced and upgraded. A main concern is the extreme radiation hardness requirements, up to 1×1016cm−2. This paper describes recent results on the radiation hardening technologies developed within the CERN RD50 Collaboration for the LHC upgrade. Silicon detectors have been designed and produced on n- and p-type 4/6in. wafers made by Float Zone, epitaxy and Czochralski technology. Their charge collection efficiency after irradiation with protons, neutron and mixed irradiation has been studied. Novel detector concepts, as 3D detectors, have been designed, produced and studied as well. Radiation induced microscopic disorder has been also investigated in Si detectors with fluences up to 1016cm−2 and correlated with the performance degradation of irradiated detectors.

Recent advances in the development of semiconductor detectors for very high luminosity colliders

For the luminosity upgrade of the LHC, the SLHC, the tracking systems of the LHC experiments need to be replaced. A main concern is the extreme radiation hardness requirement up to 1 × 10 16 cm - 2 1 MeV neutron equivalent. This paper describes an extract of recent results on radiation hardening technologies developed within the RD50 Collaboration (http://www.cern.ch/rd50) [1] for the tracker upgrades. Silicon detectors have been designed and produced on n- and p-type wafers made by Float Zone, epitaxy and Czochralski technology. Their charge collection efficiency after proton, neutron and mixed irradiation has been studied. Novel detector concepts, as 3D detectors, have been designed, produced and studied as well. Radiation induced microscopic disorder has been also investigated and correlated with the performance degradation of irradiated detectors.

First electrical characterization of 3D detectors with electrodes of the same doping type

The 3D silicon radiation detectors are very promising devices to be used in environments requiring extreme radiation hardness, such as the super-LHC experiment at CERN. A drawback of this detector is the very long and non-standard fabrication process, which makes the mass production of these devices very critical. A possible simplification of the manufacturing process relies on a new type of 3D architecture, called 3D-single-type-column detector, that we have introduced in previous works. In this paper we report on the fabrication process of the first batch of detectors and on selected results from the electrical characterization of 3D test structures, covering leakage current, capacitance and breakdown voltage measurements.

TFA pixel sensor technology for vertex detectors

Pixel microvertex detectors at the SLHC and a future linear collider face very challenging issues: extreme radiation hardness, cooling design, interconnections density and fabrication cost. As an alternative approach we present a novel pixel detector based on the deposition of a Hydrogenated Amorphous Silicon (a-Si:H) film on top of a readout ASIC. The Thin-Film on ASIC (TFA) technology is inspired by an emerging microelectronic technology envisaged for visible light Active Pixel Sensor (APS) devices. We present results obtained with a-Si:H sensor films deposited on a glass substrate and on ASIC, including the radiation hardness of this material up to a fluence of 3.5×10 15 p/cm 2.

A high-performance silicon tracker for the Compressed Baryonic Matter experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment is a fixed-target heavy-ion experiment planned at GSI's future international Facility for Antiproton and Ion Research (FAIR). CBM will study strongly interacting matter at high baryon densities where the QCD phase diagram is poorly known. The experiment applies a detector concept new to heavy-ion physics: All charged particles as well as secondary vertices from heavy-flavor decays are exclusively reconstructed in a high-performance silicon tracking system. It will be installed in a magnetic dipole field between the target and further detection systems for particle identification and calorimetry. High track densities and high collision rates require the application of most advanced silicon detectors. The technological challenges include high position resolution in thinnest possible pixel and microstrip sensors, combined with extreme radiation hardness, fast self-triggered readout and ultra low-mass mechanical supports. The article outlines the physics and detector concept of CBM and discusses the performance requirements of the silicon tracker and the beginning R&D.

03/02035 Extreme radiation hardness and light-weighted thin film indium phosphide solar cell and its computer simulation: Li, G. et al. Solar Energy Materials and Solar Cells, 2003, 75, (1–2), 307–312

03/02035 Extreme radiation hardness and light-weighted thin film indium phosphide solar cell and its computer simulation: Li, G. et al. Solar Energy Materials and Solar Cells, 2003, 75, (1–2), 307–312