Surface Radiation Damage Research Articles

Development and test of innovative Low-Gain Avalanche Diodes for particle tracking in 4 dimensions

The MIUR PRIN 4DInSiDe collaboration aims at developing the next generation of 4D (i.e., position and time) silicon detectors based on Low-Gain Avalanche Diodes (LGAD) that guarantee to operate efficiently in the future high-energy physics experiments. To this purpose, different areas of research have been identified, involving the development, design, fabrication and test of radiation-hard devices. This research has been enabled thanks to ad-hoc advanced TCAD modelling of LGAD devices, accounting for both technological issues as well as physical aspects, e.g. different avalanche generation models and combined surface and bulk radiation damage effects modelling. In this contribution, it is reviewed the progress and the relevant detector developments obtained during the research activities in the framework of the 4DInSiDe project. • TCAD modelling for the design of radiation-hard LGAD sensors for 4D tracking. • Gain layer compensation, (p ＋ - and n ＋ -doping) to preserve the gain at high fluences. • New design approach to resistive read-out sensors: DC-coupled RSD. • DC-RSD employs a direct coupling of the resistive layer to the read-out pads. • DC-coupled low resistivity strips between read-out pads to improve the resolution.

Analysis of Bulk and Surface Radiation Damage in n+ in p SFz Si Micro Strip Detectors for the Future High Luminosity Collider Experiments: TCAD Simulation and Measurements

Within the framework of CERN RD50 collaboration, several radiation damage models for n/p-SFz, n-MCz Si have been explored for the better understanding of the experimental results in radiation damage analysis of the irradiated Si detectors. In the present paper, the important review on the microscopic radiation damage model for the p-type SFz Si detector combining the surface and radiation damage effects that can be used to simulate radiation damages effects in the heavily irradiated detectors for the good comparison of the experimental data and simulation result. The surface radiation damage models were extracted from the experimental measurements on the p-MOS capacitor and Gate-Controlled Diodes irradiated by Gamma or X-ray radiations in the range of 10 to 500 Mrad (Si). Whereas, the bulk damage model microscopic parameter was extracted from the experimental (TSC, DLTS) measurements on the n in p-SFz Si microstrip detector. The radiation damage (surface and bulk) models can be fed into the commercial Synopsys TCAD device simulator program for the designing and optimization of the detector, which can be used in the very harsh radiation environment of the HL-LHC, or FCC experiment. The objective of this analysis was to verify the experimental results using the new microscopic radiation damage models on the p-SFz Si for the radiation damage analysis of p- SFz Si detectors irradiated by proton, neutron or mixed at very high fluences. The results were verified by comparison of the experimental data with TCAD simulation.

Characterization of solution grown 3D polycrystalline methylammonium lead tribromide for x-ray detection

Solution grown metal halide perovskites (MHPs) are a class of low-cost, direct conversion semiconducting materials with the potential to meet the need for large areas, high stopping power, and high sensitivity x-ray detectors. While polycrystalline MHP thin films have shown significant potential for meeting this need, their efficiencies for detecting x rays are limited by their thickness. This article presents an MHP variant, methylammonium lead tribromide (MAPB) in the form of 3D polycrystalline mosaic wafers with relatively high hole transport properties that demonstrated stable sensitivity during irradiation. An expedited and efficient detector fabrication method that did not include polishing or sintering was evaluated, and a radiograph of a brass key was produced using electron collection from the resulting wafer. However, a high dose rate was required due to very low sensitivity values. The effects of surface inhomogeneity and radiation damage were investigated as explanatory factors, and these phenomena were further characterized through IV measurements, current response as a function of electric field and x-ray dose rate, and alpha particle irradiation. The results indicated that although compromising surface quality for fabrication efficiency was the primary hindrance to the x-ray detection performance of 3D polycrystalline MAPB, stable performance could still be achieved under reasonable dose rates.

Analysis and optimal design of surface radiation hard p+n Si pixel detector: impact on signal collection using TCAD simulation

Surface radiation hard p+n Si pixel detectors are required for the science experiment at a synchrotron, and the major challenge is to improve the charge collection efficiency in the high-voltage X-ray-irradiated Si pixel detectors. Several experiments have been performed at DESY, Hamburg, Germany, within the AGIPD consortium on the test structures to extract the microscopic parameters of the X-ray-induced surface radiation damage in the detectors. The results on the microscopic parameters are fed into Cogenda Visual TCAD commercial simulation program to compare the experimental results and simulation data. A very good agreement has been recorded between the results and simulation data. In this paper, several surface radiation hard p+n Si pixel design options have been explored using a microscopic model for the improvement in the high-voltage stability of the detector and high-charge collection efficiency. A new intra-guard ring is incorporated in the design of the two adjacent p+ pixels equipped with symmetric in and outward metal overhang extensions. The proposed surface radiation hard optimal design can enhance the electric field in the gutter region of the n-Si-bulk, a region which can have a very low electric field, which is just below the Si-SiO2 interface of the detectors, and this is the major concern for the charge loss in the X-ray-irradiated detectors. The results are discussed in detail using electric field distribution in the different designs of the pixel detectors for the different X-ray doses, and an optimized p+n Si pixel detector design with an intra-guard ring structure is proposed for the experiment.

Enhanced surface radiation damage resistance in SETE-modified RAFM steel

Enhanced surface radiation damage resistance in SETE-modified RAFM steel

Fully Depleted Monolithic Active Microstrip Sensors: TCAD Simulation Study of an Innovative Design Concept.

The paper presents the simulation studies of 10 m pitch microstrips on a fully depleted monolithic active CMOS technology and describes their potential to provide a new and cost-effective solution for particle tracking and timing applications. The Fully Depleted Monolithic Active Microstrip Sensors (FD-MAMS) described in this work, which are developed within the framework of the ARCADIA project, are compliant with commercial CMOS fabrication processes. A set of Technology Computer-Aided Design (TCAD) parametric simulations was performed in the perspective of an upcoming engineering production run with the aim of designing FD-MAMS, studying their electrical characteristics, and optimizing the sensor layout for enhanced performance in terms of low capacitance, fast charge collection, and low-power operation. A fine pitch of 10 m was chosen to provide high spatial resolution. This small pitch still allows readout electronics to be monolithically integrated in the inter-strip regions, enabling the segmentation of long strips and the implementation of distributed readout architectures. The effects of surface radiation damage expected for total ionizing doses of the order of 10 to 10 krad were also modeled in the simulations. The results of the simulations exhibit promising performance in terms of timing and low power consumption and motivate R&D efforts to further develop FD-MAMS; the results will be experimentally verified through measurements on the test structures that will be available from mid-2021.

Electrical characterization of surface properties of the ATLAS17LS sensors after neutron, proton and gamma irradiation

The high luminosity upgrade of the Large Hadron Collider, foreseen for 2027, requires the replacement of the ATLAS Inner Detector with a new all-silicon Inner Tracker (ITk). The expected total integrated luminosity of 4000 fb−1 means that the strip part of the ITk detector will be exposed to a large radiation fluence of up to Φeq = 1.6 × 1015 1 MeV neq/cm and an ionizing dose of 0.66 MGy, including a safety factor of 1.5. Radiation-hard n+-in-p micro-strip sensors for use in the ITk have been developed by the ATLAS ITk Strip Sensor collaboration and produced by Hamamatsu Photonics K.K. In this paper, the results obtained from the electrical characterization of the latest barrel ATLAS17LS sensor prototype, before and after irradiation, are shown.Surface properties of the long-strip barrel, full-sized and miniature sensors have been studied before and after proton, neutron and gamma irradiation up to the maximal fluences and radiation doses specified for the ITk Strip tracker. Sensors have been irradiated by protons at CYRIC, Tohoku University (Japan), the Proton Irradiation Facility at CERN, Karlsruhe Inst. Tech. (Germany) and at the University of Birmingham (UK), by neutrons from the Ljubljana TRIGA reactor (Slovenia) and by gamma rays from the 60Co source in UJP Praha (Czech Republic).It has been verified that the surface radiation damage does not influence the sensor functionality. The breakdown voltage is well above the maximum operational voltage. All the tested surface parameters, such as the inter-strip resistance and capacitance, coupling capacitance and bias resistance satisfy the ATLAS ITk specifications for strip sensors.

Measurements of surface and bulk radiation damage effects in silicon detectors for Phase-2 CMS Outer Tracker

In this work we address the effects of bulk and surface damages on detectors fabricated by Hamamatsu on standard float zone (FZ) p-type material with an active thickness of 290 µm or thinned to 240 µm. In order to disentangle the effects of the two main radiation damage mechanisms, ionization effects and atomic displacement, the structures underwent two types of radiation: X-ray with doses from 0.05 to 70 Mrad (SiO2) and neutron in the range of 1−10 × 1014 neq/cm21MeV equivalent. The combined surface and bulk damage could be investigated in structures that underwent both types of irradiation. A wide set of measurements has been carried out on the test structures for a complete characterization.

Characterization of irradiated p-type silicon detectors for TCAD surface radiation damage model validation

In this work we address the effects of surface radiation damage on detectors fabricated on high-resistivity p-type FZ ⟨ 100⟩ substrates by Hamamatsu Photonics (HPK) and by Infineon Technologies (IFX). Test structures underwent a wide set of measurements before and after X-ray irradiation with doses from 0.05 to 100 Mrad (SiO2) in order to extract the integrated interface trap density (NIT) and the oxide charge (QOX) peculiar to different vendors, processes and technology options. These parameters can be then used as inputs to TCAD simulation tools. On the basis of the new experimental evidences at these high doses, the TCAD numerical model has been updated considering two main bands of defects, one acceptor and one donor, extended to the whole silicon bandgap and simulating the net effect of the radiation-induced acceptor-like and donor-like defects. The comparison between simulation findings and measured macroscopic electric behaviour, e.g. in terms of C–V curves of MOS capacitors has been used as cross-check for model validation purposes. By means of the same modelling scheme it is possible to reproduce the I–V curves of gated-diodes and the interstrip resistance as a function of the dose from 0.05 to 100 Mrad (SiO2) for the range of technology and design options investigated. The good agreement between simulations and measurements would support the use of this TCAD surface radiation damage model as a predictive tool to optimize the design and the operations of the new generation of silicon detectors for the future High Energy Physics experiments.

Design and development of radiation hard p+n Si pixel detector for the next generation photon science experiment

Science, at next generation photon science experiment requires radiation hard p+n Si pixel detector for the X-ray imaging. The choice of an appropriate surface radiation hard X-ray thick Si detector design is a challenging task for the long-term operation of the experiment for the different application that involves up to 25 KeV X-ray energy especially in the material science. The test structure for e.g. prototype p+n Si microstrip detector was fabricated at BEL, Bengaluru, India. The current–voltage and capacitance–voltage characteristic of the detector was measured. The experimental macroscopic parameters are used for the designing of the p+n Si pixel detector. The Visual TCAD semiconductor device simulator from Cogenda was used to compare the simulated and experimental results of the prototype detector to see the electric field distribution in the detector. The breakdown performance of the detector has been discussed using simulation result. The experimentally observed microscopic parameters Nfixox (fixed oxide charge) and Nit (interface trapped charge) can be used in the simulation in order to understand the surface radiation damage performance of the detector. The influences of various device and process parameters on the macroscopic parameters of the detector are shown.In this paper, the influence of the X-ray radiation damage on the electrical performance of the p+n Si pixel detector is shown. On the basis of TCAD simulation and experimental measurement, a radiation-hard p+n silicon pixel sensor design, process, device parameter, and specification is proposed for the next generation photon science experiment like Eu-XFEL.

Measurements and simulations of surface radiation damage effects on IFX and HPK test structures

Radiation damage effects at High Luminosity LHC (HL-LHC) expected fluences and total ionizing doses (TID) will impose very stringent constraints in terms of radiation resistance of silicon detectors. In this work, we address the effects of surface damage on detectors fabricated on p-type substrates by two different foundries. Starting from standard test structure measurements, the interface trap state density and the oxide charge can be extracted for each specific foundry before and after irradiation with X-rays with doses ranging from 0.05 to 100 Mrad(SiO2). These parameters are then used as inputs to the Technology-CAD simulation tools, aiming at evaluating the effects of oxide charge density and interface trap density variation with the dose on MOS capacitor capacitances and interstrip resistances. The good agreement between simulation results and measurements would support the use of the model as a predictive tool to optimize the design and the operation of novel silicon detectors in the HL-LHC scenario.

Surface evolution and radiation damage of a zirconolite glass-ceramic by Au ion implantation

Ion implantation using particle accelerators is a promising avenue to emulate the property-controlling microstructures created in nuclear materials. In the present study, the 21 MeV Au ion implantations with fluence up to 1 × 1015 ion/cm2 have been conducted on the surface of a zirconolite glass-ceramic. The microstructure modifications on the surface have been investigated by X-ray diffraction, Raman spectrometry, scanning electron microscopy and transmission electron microscopy. The amorphous behavior of the crystalline zirconolite and the structural change in the glassy phase has been identified subject to different fluences. The amorphization of zirconolite crystals occurred on the surface of sample subjected to 1 × 1014 ion/cm2 and the deformation of glass and zirconolite crystals near the surface were observed at the fluence of 1 × 1015 ion/cm2.

Advances on TCAD numerical modelling of radiation damage effects in silicon detectors for HL-LHC operations

Abstract In this work we present a surface radiation damage effects model based on the introduction of amphoteric, uniform energy band distributed deep-level defects. The main characteristic parameters of the surface damage, e.g. the equivalent oxide charge and interface trap densities, have been extracted from experimental measurements carried out on test structures manufactured by the three foundries: HPK, FBK and Infineon. The surface damage model has been coupled with a bulk damage model based on multiple, single-level defects with tunable capture-cross sections. The model is able to reproduce the measurements carried out on irradiated test structures in terms of C–V curves, interstrip resistance as well as charge collection of segmented detectors.

Analysis of surface radiation damage effects at HL-LHC fluences: Comparison of different technology options

Radiation damage effects at High Luminosity LHC (HL-LHC) fluences greater than 2.2×1016n∕cm2 1 MeV equivalent and total ionizing doses (TID) greater than 1 Grad will impose very stringent constraints in terms of radiation resistance of solid-state detectors. To cope with this design challenge, TCAD tools can be used to study different technology and design options, in order to optimize the performance of silicon detectors in terms of inter-electrode isolation and charge collection properties. A comprehensive modeling approach based on combined bulk and surface damage effects accounting for a limited number of measurable parameters needs therefore to be developed and validated over different technology options. In this work, we mainly focus on the effects of surface damage on detectors fabricated on p-type substrates by different providers. Actually, starting from standard test structure measurements (i.e. MOS capacitors, gated diodes), the integrated interface trap state density (NIT) and the oxide charge (QOX) can be extracted for different vendors and used as input parameter to the simulation tools. Test structures under study include MOS capacitors, gated-diodes, fabricated both at Hamamatsu Photonics (Japan) and at Infineon (Austria). Using High-Frequency (HF) and Quasi-Static (QS) C–V characteristics and current–voltage (I–V) measurements, the effective oxide charge density (NEFF), the surface generation velocity (s0) and the interface trap density (DIT) have been determined and compared for the two technologies before and after irradiation with X-rays with doses ranging from 0.05 to 20 Mrad(SiO2). A detailed simulation analysis on MOS capacitor capacitances and gated diode currents has been carried out, varying the previously mentioned parameters, with the aim to evaluate the effects of oxide charge density and interface trap density increase with the dose. The separate effects of different types of interface trap states have been considered as well, by varying one by one the total density of donor- and acceptor-type trap states, respectively. The effects of different trap energy distributions and capture cross sections have been evaluated within Synopsys Sentaurus TCAD device simulator by means of steady-state, AC and transient analyses. The good agreement obtained for both vendors would support the use of the model as a predictive tool to optimize the design and the operation of novel solid-state detectors in the HL-LHC scenario.

Electron attachment to molecules in a cluster environment: suppression and enhancement effects

Cluster environments can strongly influence dissociative electron attachment (DEA) processes. These effects are important in many applications, particularly for surface chemistry, radiation damage, and atmospheric physics. We review several mechanisms for DEA suppression and enhancement due to cluster environments, particularly due to microhydration. Long-range electron–molecule and electron–cluster interactions play often a significant role in these effects and can be analysed by using theoretical models. Nevertheless many observations remain unexplained due to complexity of the physics and chemistry of interaction of DEA fragments with the cluster environment.

Effects of Interface Donor Trap States on Isolation Properties of Detectors Operating at High Luminosity LHC (HL-LHC)

The very high radiation fluences expected at the high-luminosity large hadron collider (LHC) impose new challenges in terms of design of radiation resistant silicon detectors. The choice to use p-type substrates to improve the charge collection efficiency involves an optimization of the strip isolation to interrupt the inversion layer between the $n^{+}$ implants, limiting the breakdown voltage. To this purpose, TCAD modeling and simulation schemes, already developed and validated at typical LHC fluences have to be adapted to take into account effects usually neglected at lower fluences. To better understand in a comprehensive framework, the complex and articulated phenomena related to bulk and surface radiation damage, measurements on test structures and sensors, as well as TCAD simulations related to bulk, surface and interface effects, have been carried out. In particular, we have studied the properties of the SiO2 layer and of the Si-SiO2 interface, using MOS capacitors and gate-controlled diodes (gated diodes) manufactured by different vendors on a high-resistivity p-type silicon before and after irradiation with X-rays in the range from 50 krad to 10 Mrad. In this paper, we present the results of the experimental characterizations as well as the simulation findings, in order to analyze the effects of the interface traps on the strip isolation. This analysis helps us to validate the model and to identify the most sensitive technological and design parameters to be optimized for the design of advanced 2-D and 3-D silicon radiation detectors.

Combined Bulk and Surface Radiation Damage Effects at Very High Fluences in Silicon Detectors: Measurements and TCAD Simulations

In this work we propose a new combined TCAD radiation damage modelling scheme, featuring both bulk and surface radiation damage effects, for the analysis of silicon detectors aimed at the High Luminosity LHC. In particular, a surface damage model has been developed by introducing the relevant parameters (NOX, NIT) extracted from experimental measurements carried out on p-type substrate test structures after gamma irradiations at doses in the range 10-500 Mrad(Si). An extended bulk model, by considering impact ionization and deep-level cross-sections variation, was included as well. The model has been validated through the comparison of the simulation findings with experimental measurements carried out at very high fluences (2 10^16 1 MeV equivalent n/cm^2) thus fostering the application of this TCAD approach for the design and optimization of the new generation of silicon detectors to be used in future HEP experiments.

Measurement of the electric-field and time dependence of the effective oxide-charge density of the Si-SiO2 system

The surface radiation damage of SiO2 grown on high-ohmic n-type Si, as used for the fabrication of segmented silicon sensors, has been investigated. A circular p-MOSFET, biased in inversion at a field in the SiO2 of about 500 kV/cm, has been irradiated by X-rays up to a dose of about 17 kGy(SiO2) in different irradiation steps. Before and after each irradiation, the gate voltage has been cycled from inversion to accumulation conditions and back, and the threshold voltage of the MOSFET and the hole mobility at the Si-SiO2 interface determined. From the threshold voltage, the effective oxide-charge density is calculated. The measurement of the drain-source current during the irradiation allows the study of the change of the oxide-charge density during irradiation. Results on the dose dependence of the effective oxide-charge density, the charging-up and discharging of border traps when changing the gate voltage, and the hole mobility at the Si-SiO2 interface are presented.

Application of helium ion microscopy to nanostructured polymer materials

AbstractHelium ion microscopy (HIM) is a relatively new high-resolution nanotechnology imaging and nanofabrication tool. HIM offers a near-molecular resolution (approaching that of TEM) combined with a simplicity of sample preparation and high depth of field similar to SEM. Simultaneously, the technique is not limited by the surface roughness as scanning probe microscopy (SPM) techniques or by the surface charging or radiation damage like SEM. In our review, we consider general principles, advantages, and prospects of HIM application in polymer science. Examples of high-resolution imaging of polymer-based nanocomposites, polymer nanoparticles, nanofibers, nanoporous materials, polymer nanocrystals, biopolymers, and polymer-based photovoltaic and sensor devices are presented. We compare the HIM’s applicability with other modern imaging techniques: SPM and SEM.

Radiation-Induced Nano-Explosions at the Solid Surface: Near Surface Radiation Damage in CR-39 Polymer

New measurements of fission fragment and alpha particle induced surface damage in the most sensitive and commonly used nuclear track detector CR-39 are presented here. Precisely designed and optimized exposure and chemical etching experiments are employed to unfold the structure of radiation induced surface damage (RISD). Delay in the startup of the chemical etching of latent tracks or surface radiation damage is measured and is found to contain important information about the structure of the surface damage. Simple atomic scale pictures of RISD and its chemical etching are developed in an empirical manner. Theoretical model and experimental findings coherently compose a realistic picture of early or femtosecond evolution of RISD.