Improvement Of Radiation Tolerance Research Articles

Design and evaluation of UKRI-MPW0: An HV-CMOS prototype for high radiation tolerance

High-Voltage CMOS (HV-CMOS) sensors are emerging as a prime candidate for future tracking applications that have extreme requirements on material budget, pixel granularity, time resolution and radiation tolerance. This article presents a new HV-CMOS prototype chip, UKRI-MPW0, aimed at pushing some of the boundaries of these sensors. This HV-CMOS chip implements a novel sensor cross-section which is optimised for backside biasing to unprecedented high voltages. Preliminary measurements have shown the chip is able to withstand high bias voltages (>600V) much beyond the state of the art, thus promising a large improvement in radiation tolerance. The design details and initial performance evaluation are presented in this paper.

Amorphous intergranular films mitigate radiation damage in nanocrystalline Cu-Zr

Nanocrystalline metals are promising radiation tolerant materials due to their large interfacial volume fraction, but irradiation-induced grain growth can eventually degrade any improvement in radiation tolerance. Therefore, methods to limit grain growth and simultaneously improve the radiation tolerance of nanocrystalline metals are needed. Amorphous intergranular films are unique grain boundary structures that are predicted to have improved sink efficiencies due to their increased thickness and amorphous structure, while also improving grain size stability. In this study, ball milled nanocrystalline Cu-Zr alloys are heat treated to either have only ordered grain boundaries or to contain amorphous intergranular films distributed within the grain boundary network, and are then subjected to in situ transmission electron microscopy irradiation and ex situ irradiation. Differences in defect density and grain growth due to grain boundary complexion type are then investigated. When amorphous intergranular films are incorporated within the material, fewer and smaller defect clusters are observed while grain growth is also limited, leading to nanocrystalline alloys with improved radiation tolerance.

Effect of carbon nanotube on radiation resistance of CNT-Cu nanocomposite: MD simulation

Carbon nanotubes are one of the candidates for the reinforcement of metals for numerous applications. In this study, the effect of CNT on the primary radiation damage of CNT-Cu nanocomposite was investigated using molecular dynamics simulations. The simulations were performed by considering primary knock-on atom with 3 and 6 keV kinetic energies in the radial velocity direction (perpendicular to the cylinder axis) at various distances from the armchair CNT with (28, 28) chirality. Equivalent simulations in the single copper crystal and crystal containing cylindrical nanovoid (“CNV”) were performed for comparison. The results represent an improvement in radiation tolerance of copper composed with CNT nanofiller. In this material, CNT not only plays a sink role for point defects, but also it acts as a barrier to extend the displacement cascade. Some fluctuations in the number of the bulk vacancy around CNT-Cu interface were observed. The reason for this behavior was discussed.

Influence on Particle Double-Network Gels by Gamma Irradiation and Improvement of Radiation Tolerance

Influence on Particle Double-Network Gels by Gamma Irradiation and Improvement of Radiation Tolerance

Amorphous Intergranular Films Mitigate Radiation Damage in Nanocrystalline Cu-Zr

Nanocrystalline metals are promising radiation tolerant materials due to their large interfacial volume fraction, but irradiation-induced grain growth can eventually degrade any improvement in radiation tolerance. Therefore, methods to limit grain growth and simultaneously improve the radiation tolerance of nanocrystalline metals are needed. Amorphous intergranular films are unique grain boundary structures that are predicted to have improved sink efficiencies due to their increased thickness and amorphous structure, while also improving grain size stability. In this study, ball milled nanocrystalline Cu-Zr alloys are heat treated to either have only ordered grain boundaries or to contain amorphous intergranular films distributed within the grain boundary network, and are then subjected to in situ transmission electron microscopy irradiation and ex situ irradiation. Differences in defect density and grain growth due to grain boundary complexion type are then investigated. When amorphous intergranular films are incorporated within the material, fewer and smaller defect clusters are observed while grain growth is also limited, leading to nanocrystalline alloys with improved radiation tolerance.

Investigation of the Influence of Temperature and Annealing on the Radiation Hardness of Silicon Mach–Zehnder Modulators

Optical links are vital components in the data transmission systems of high energy physics (HEP) experiments at CERN. With the ever higher beam fluxes achieved by the Large Hadron Collider, the optical components have to withstand higher radiation levels and handle ever-increasing data volumes. To face these challenges, the use of silicon photonics (SiPh) Mach-Zehnder modulators (MZMs) in the next generation of optical transceivers for HEP experiments is currently being investigated. In this paper, the dependence of the radiation hardness of custom-designed SiPh MZMs on temperature is reported, including the observed improvement in radiation tolerance at low operating temperatures that are closer to the typical temperatures found in HEP experiments. Furthermore, postirradiation annealing measurements of the devices were performed. An effective annealing method has been found by applying a forward current to the MZMs, leading to an almost immediate and full recovery of the device after irradiation up to 3 MGy. This enhanced device recovery method could effectively increase the radiation hardness tremendously in applications with low dose rates and periodic shutdown times.

Radiation Imaging Detectors Using SOI Technology

Silicon-on-Insulator (SOI) technology is widely used in high-performance and low-power semiconductor devices. The SOI wafers have two layers of active silicon (Si), and normally the bottom Si layer is a mere physical structure. The idea of making intelligent pixel detectors by using the bottom Si layer as sensors for X-ray, infrared light, high-energy particles, neutrons, etc. emerged from very early days of the SOI technology. However, there have been several difficult issues with fabricating such detectors and they have not become very popular until recently. This book offers a comprehensive overview of the basic concepts and research issues of SOI radiation image detectors. It introduces basic issues to implement the SOI detector and presents how to solve these issues. It also reveals fundamental techniques, improvement of radiation tolerance, applications, and examples of the detectors. Since the SOI detector has both a thick sensing region and CMOS transistors in a monolithic die, many ideas have emerged to utilize this technology. This book is a good introduction for people who want to develop or use SOI detectors.

Comparison of gamma radiation performance of a range of CMOS a/D converters under biased conditions

Radiation effects on analog and mixed signal semiconductor devices are a major concern in space and nuclear applications. Significant degradation has been observed in A/D converters in a radiation environment. In fact, recent advances in A/D converters have further reduced the radiation tolerance of these converters on account of their complex circuitry. This paper studies the effects of gamma radiation on several properties (offset error, gain error, integral non linearity etc.) of a whole range of A/D converters under biased conditions. A comparative study of their performance is presented. Four major types of A/D converters, namely- flash, successive approximation, integrating and sigma-delta type, are selected for a detailed evaluation and comparison. Significant degradation of the power supply currents was observed in the biased samples during radiation. Significant improvement in radiation tolerance after adjustment of the offset and calibration registers in the high resolution sigma delta converters can be achieved. All the results and experimental observations are presented

Radioprotective effect of N-acetylcysteine on granulocyte/macrophage colony-forming cells of human bone marrow.

N-Acetylcysteine, known as a radical scavenger, was examined for its influence on the radiotolerance of progenitor cells of granulocytopoiesis. Added before and after irradiation in a dose of 2 mg/ml to suspension cultures of non-adherent low-density human bone marrow cells N-acetylcysteine (AcCys) clearly improved the survival. The D0 value of the survival curve for granulocyte/macrophage colony-forming cells increased by a factor of 1.56 as compared to non-treated control suspensions. The improvement of radiation tolerance is probably not only based on the radical scavenger properties (radioprotective component) of AcCys, but also on the support of repair processes.

Radiation tolerance of double layer field oxides

A radiation-hard field oxide has been fabricated for integrated circuits, eliminating the radiation-induced field inversion observed with pyrogenic field oxides. The radiation-hardened oxide was fabricated in conventional silicon integrated circuit process techniques and does not degrade under subsequent thermal stresses (up to 1000 degrees C). The field oxide is built up of a double layer consisting of a thick, chemically deposited and doped SiO/sub 2/ layer on top of a thin, thermally grown SiO/sub 2/ film. The influence of the dopants of the CVD (chemical vapor deposited') oxide as well as the annealing temperature on the radiation hardness of the field oxide is examined in order to find optimized process parameters. Compared to thermal oxides, a 2.5-order-of-magnitude improvement in radiation tolerance is observed with regard to the threshold voltage shift. The double layer field oxide can replace the thermal oxide in VLSI bipolar and MOS technologies. The elimination of guard bands, closed cell design, and gated insulator structures in MOS circuits is rendered possible. Significant improvement in speed and circuit density can be achieved by eliminating additional stray capacitance and space for guard structures.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Radiation effects on UHF power MOSFETs

The effects of ionizing radiation of UHF power MOSFETs are studied. It is found that a power MOSFET amplifier exhibits little change in output power and efficiency in the linear region, but it is seriously degraded in the saturation region. The reason for this degradation is an increase in on-resistance and a decrease in the maximum current, both caused by radiation-induced interface states. A MOSFET exposed to radiation while it is operating as an amplifier at 860 MHz has a different threshold voltage shift than one not operating at high-frequency. This phenomenon can be explained by the annealing effect of the high-frequency electric field across the gate. For improvement in radiation tolerance, a device with a thinner thermal oxide film on the offset region is proposed and discussed. >

Radiation Hardened Silicon Devices Using a Novel Thick Oxide

A radiation hardened thick oxide technology is proposed. It utilizes a double layer consisting of a thick chemically deposited SiO2 over a thin thermal SiO2. In npn transistors, a 1.5 order of magnitude improvement in radiation tolerance is observed when this technology is combined with a highly doped Si surface layer.

Reduction of Long-Term Transient Radiation Response in Ion Implanted GaAs FETs

The long-term transient radiation response in ion implanted GaAs FETs induced by flash x-ray or electron pulses has been reduced by the incorporation of a deep buried p-layer beneath the active n-layer. Reductions in the change in drain current of up to two orders of magnitude were measured in FETs with the buried p-layer compared to FETs with only an n-implanted channel following a 100 rad x-ray pulse. This improvement in radiation tolerance is attributed to shielding of the active n-layer by the conducting p-layer from the effects of radiation induced trapped substrate charge.

MOS Hardening Approaches for Low-Temperature Applications

Charge buildup in irradiated MOS devices is significantly more severe at low temperatures than at room temperature. Approaches for counteracting this problem are considered in this paper, including: (1) careful selection of the applied field; (2) ion implantation of the oxide; (3) use of a thin oxide. Experimental and analytical results are presented and it is demonstrated that the applied field dependence of flatband voltage shift in MOS capacitors irradiated at 77°K can be accounted for in terms of the field dependence of electron yield and the transport of holes at high fields. Analysis of ion implantation effects indicates that a significant improvement in radiation tolerance should be achievable by this method. A simultaneous consideration of the effects of oxide thickness and applied field on charge buildup in an unimplanted oxide suggests that reducing the thickness to ?500 A° will largely eliminate low temperature problems in a steady-state ionizing radiation environment as long as the applied voltage is ? 10V.