Displacement Damage Effects Research Articles

Resistance State Locking in CBRAM Cells Due to Displacement Damage Effects

Two different displacement damage experiments were performed on CBRAM cells. In one experiment, conductive bridging random access memory (CBRAM) cells were exposed to 14 MeV neutrons to a total fluence of $3.19 \times 10^{13}$ n/cm2. In the second test, CBRAM cells were bombarded with 200 keV Si2+ ions. In both the experiments, the high resistance and low resistance states (LRSs) of the cells were observed to converge with increasing particle fluence. After reaching a 14 MeV neutron fluence of $2.93 \times 10^{{{13}}}$ n/cm2, the CBRAM cells became irrecoverably locked into their final resistance state. In situ testing during heavy ion exposure showed a steady decrease in the resistance state of each cell with each successive exposure to the beam. The devices eventually became locked in an LRS.

Nuclear microprobe investigation of the effects of ionization and displacement damage in vertical, high voltage GaN diodes

Radiation responses of high-voltage, vertical gallium-nitride (GaN) diodes were investigated using Sandia National Laboratories’ nuclear microprobe. Effects of the ionization and the displacement damage were studied using various ion beams. We found that the devices show avalanche effect for heavy ions operated under bias well below the breakdown voltage. The displacement damage experiments showed a surprising effect for moderate damage: the charge collection efficiency demonstrated an increase instead of a decrease for higher bias voltages.

Correction to “Synergistic Effect of Ionization and Displacement Damage in NPN Transistors Caused by Protons With Various Energies” [Jun 15 1375-1382

Correction to “Synergistic Effect of Ionization and Displacement Damage in NPN Transistors Caused by Protons With Various Energies” [Jun 15 1375-1382

(Invited) Displacement Damage and Single Event Effects in AlGaN/GaN HEMTs

Superior advantages of AlGaN/GaN high electron mobility transistors (HEMTs) from a size, weight, and power perspective make this technology desirable for use in outer space applications. However, the harsh environment in space includes bombardment of various types of radiation, which can degrade the performance and reliability of these devices. Displacement damage refers to atomic displacement within the semiconductor crystal lattice. This is permanent damage that permanently impacts the device characteristics. High-energy (2 meV) protons at various fluences, up to 6 x 1014 H+/cm2 were used to investigate the impact of displacement damage on AlGaN/GaN HEMTs. A reduction in the maximum drain current is observed, which is also attributed to a decrease in the two-dimensional electron gas (2DEG) mobility and sheet carrier density. A roughened interface between the AlGaN and GaN layers from atomic recoiling during irradiation has been identified as the mechanism for this mobility decrease. We have attributed the change in sheet carrier density to radiation-induced recombination centers created within the GaN. This results in a decrease in the Fermi level of the GaN, which also decreases the number of mobile electrons in 2DEG. Single event transients generated from energetic particles passing through the device create electrons and holes, which are collected at the terminals, are a potential reliability issue for the GaN HEMTs. A nondestructive focused pulsed-laser technique is used to investigate single event effects in the GaN HEMT devices, both before and after proton irradiation. Characteristics such as the peak amplitude, width, and total charge collected are investigated at various bias conditions and at different locations in the GaN HEMTs. The maximum charge collected is identified to be at the location corresponding to the peak electric field within the device. Defects within the GaN HEMTs induced by proton irradiation increase the time constant of the single event decay. Three distinct trapping time constants have been identified from extracted curve fits to the single event decay transient.

Displacement damage in bit error ratio performance of on-off keying, pulse position modulation, differential phase shift keying, and homodyne binary phase-shift keying-based optical intersatellite communication system.

Displacement damage (DD) effect induced bit error ratio (BER) performance degradations in on-off keying (OOK), pulse position modulation (PPM), differential phase-shift keying (DPSK), and homodyne binary phase shift keying (BPSK) based systems were simulated and discussed under 1 MeV neutron irradiation to a total fluence of 1×1012 n/cm2 in this paper. Degradation of main optoelectronic devices included in communication systems were analyzed on the basis of existing experimental data. The system BER degradation was subsequently simulated and the variations of BER with different neutron irradiation location were also achieved. The result shows that DD on an Er-doped fiber amplifier (EDFA) is the dominant cause of system degradation, and a BPSK-based system performs better than the other three systems against DD. In order to improve radiation hardness of communication systems against DD, protection and enhancement of EDFA are required, and the use of a homodyne BPSK modulation scheme is a considered choice.

Influence of Ionizing Radiation and the Role of Thiol Ligands on the Reversible Photodarkening of CdTe/CdS Quantum Dots.

We investigate the influence of high energy photons and thiol ligands on the photophysical properties of sub-monolayer CdTe/CdS quantum dots (QDs) immobilized in porous silica (PSiO2) scaffolds. The highly disperse, uniform distributions of QDs in a three-dimensional PSiO2 framework ensure uniform interaction of not only radiation but also subsequent surface repassivation solutions to all immobilized QDs. The high optical densities of QDs achieved using PSiO2 enable straightforward monitoring of the QD photoluminescence intensities and carrier lifetimes. Irradiation of QDs in PSiO2 by high energy photons, X-rays, and γ-rays leads to dose-dependent QD photodarkening, which is accompanied by accelerated photooxidative effects in ambient environments that give rise to blue-shifts in the peak QD emission wavelength. Irradiation in an oxygen-free environment also leads to QD photodarkening but with no accompanying blue-shift of the QD emission. Significant reversal of QD photodarkening is demonstrated following QD surface repassivation with a solution containing free-thiols, suggesting reformation of a CdS shell, etching of surface oxidized species, and possible reduction of photoionized dark QDs to a neutral, bright state. Permanent lattice displacement damage effects may contribute toward some irreversible γ radiation damage. This work contributes to an improved understanding of the influence of surface ligands on the optical properties of QDs and opens up the possibilities of engineering large area, low-cost, reuseable, and flexible QD-based optical radiation sensors.

Structure of Defects and Microstructure Evolution in Oxide Ceramics – Role of Electronic Excitation and Selective Displacement Damage

Fluoriteand spinel-type oxide ceramics, such as yttria-stabilized zirconia, ceria, magnesium aliminate spinel, are known to be exceptionally resistant to irradiation damage with energetic particles. Those oxide compounds, thereofore, have potential applications to advanced nuclear fuels and innert matrices of transmutaion targets. Fundamental understanding of radiation damage is apparently essential to assess the microstructure stability of fuel/target materials under the hostile environment. In this presentation, structure and stability of radiation-induced defects in the oxide ceramics is reported. Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) is utilized to examine the following topics focucing on role of electronic excitation and selective displacement damage: (1) effects of selective displacement damage of oxygen sublattice in fluorite-type oxides, such as stabilided cubic ZrO2, CeO2 [1-3], (2) atomic structure of ion tracks in CeO2 and MgAl2O4 induced by swift heavy ions, and microstructure evolution at high fluences under overlapping irradiation of high density electronic excitation damage [4-6], and (3) production and stability of defects in MgAl2O4 and alumina (-Al2O3) under synergistic irradiation with dispacement damage and electronic excitation [7].

电荷耦合器件中子辐照诱发的位移效应

Displacement damage effects due to neutron irradiations of charge coupled devices were presented through the analysis of the dark signals behavior in pixel arrays. When the fluence of neutron reached the predetermined point,the change of dark signal,dark signal non-uniformity,charge transfer efficiency and saturated output signal was measured off line. The major effect of neutron induced displacement damage on charge coupled device is the increase in dark signals as a result of carrier generation in the bulk depletion region of the pixel. Although the increase in the mean dark signals with neutron irradiation is important,the dark signals non-uniformity is generally the biggest concern for charge coupled device applications in space. Very large dark signals pixels can be produced when a collision occurs in a high electric field region of a pixel as a result of electric field enhanced emission. Another important performance parameter for a charge coupled device is the charge transfer efficiency,which is the fraction of signal charge transferred from pixel to pixel during read out. If a signal charge is trapped by neutron induced defect,and remains trapped for more than one clock cycle,it will be lost from the signalcharge packet. Saturation output signal voltage does not have any obvious degradation even at the highest DDD level. The research will help the designers to know the radiation damage in charge coupled device and improve the tolerance by radiation hardening design.

Effects of Proton-Induced Displacement Damage on Gallium Nitride HEMTs in RF Power Amplifier Applications

The effects of proton-induced displacement damage in GaN HEMTs on circuit-level RF power amplifier parameters such as circuit gain, stability, and RF output power are presented. The results are explained based on the device-level degradation. Commercial-off-the-shelf GaN HEMTs from two manufacturers were compared. Differences are observed in both device and circuit level responses. Suggestions to mitigate the negative effects of displacement damage on GaN based amplifiers are also provided.

Proton Irradiation as a Screen for Displacement-Damage Sensitivity in Bipolar Junction Transistors

NPN and PNP bipolar junction transistors of varying sizes are irradiated with 4-MeV protons and 10-keV X-rays to determine the amount of ionization-related degradation caused by protons and calculate an improved estimate of displacement-related degradation due to protons. While different ratios of degradation produced by displacement damage and ionization effects will occur for different device technologies, this general approach, with suitable margin, can be used as a screen for sensitivity to neutron-induced displacement damage. Further calculations are performed to estimate the amount of degradation produced by 1-MeV equivalent neutron displacement damage compared to that produced by the displacement damage due to protons. The results are compared to previous work.

Neutron irradiation effects on the microstructural development of tungsten and tungsten alloys

Data on the microstructural development of tungsten (W) and tungsten rhenium (Re) alloys were obtained after neutron irradiation at 400–800 °C in the Japan Materials Testing Reactor (JMTR), the experimental fast test reactor Joyo, and the High Flux Isotope Reactor (HFIR) for irradiation damage levels in the range of 0.09–1.54 displacement per atom (dpa). Microstructural observations showed that a small amount of Re (3–5%) in W–Re alloys is effective in suppressing void formation. In W–Re alloys with Re concentrations greater than 10%, acicular precipitates are the primary structural defects. In the HFIR-irradiated specimen, in which a large amount of Re was expected to be produced by the nuclear transmutation of W to Re because of the reactor's high thermal neutron flux, voids were not observed even in pure W. The synergistic effects of displacement damage and solid transmutation elements on microstructural development are discussed, and the microstructural development of tungsten materials utilized in fusion reactors is predicted.

Physical Processes and Applications of the Monte Carlo Radiative Energy Deposition (MRED) Code

MRED is a Python-language scriptable computer application that simulates radiation transport. It is the computational engine for the on-line tool CRÈME-MC. MRED is based on c++ code from Geant4 with additional Fortran components to simulate electron transport and nuclear reactions with high precision. We provide a detailed description of the structure of MRED and the implementation of the simulation of physical processes used to simulate radiation effects in electronic devices and circuits. Extensive discussion and references are provided that illustrate the validation of models used to implement specific simulations of relevant physical processes. Several applications of MRED are summarized that demonstrate its ability to predict and describe basic physical phenomena associated with irradiation of electronic circuits and devices. These include effects from single particle radiation (including both direct ionization and indirect ionization effects), dose enhancement effects, and displacement damage effects. MRED simulations have also helped to identify new single event upset mechanisms not previously observed by experiment, but since confirmed, including upsets due to muons and energetic electrons.

Impact of proton fluence on DC and trapping characteristics in InAlN/GaN HEMTs

Robustness of InAlN/GaN devices under proton radiation is investigated. Several proton fluences ranging from 1×1014 to 4×1014 have been considered on two typologies of devices. Displacement damage is found to be the major responsible of device DC degradation leading to threshold voltage positive shift, ON resistance increase and drain current decrease, in all cases well correlated with proton fluence. Negligible difference is noticed in displacement damage effects measured on different device typologies. Furthermore, device geometry does not influence the impact of proton radiation on main DC parameters, either if gate width or length are considered. Radiation significantly affects trapping properties. A good correlation between the so-called current collapse increase and proton fluence is demonstrated when a high gate drain voltage value is imposed as trapping condition. Moreover radiation enhances the contribution of dynamic ON resistance and transconductance peak variation on current collapse increase.

Synergistic Effect of Ionization and Displacement Damage in NPN Transistors Caused by Protons With Various Energies

Based on 2N2222 NPN bipolar junction transistors (BJTs), synergistic effect between ionization and displacement defects induced by 3 MeV, 5 MeV and 10 MeV protons were researched. High-energy protons can be incident upon the silicon (Si) BJTs, producing displacement defects in silicon bulk and ionization damage in the oxide layer of BJTs, respectively. Both ionization and displacement damage result in the degradation of current gain of BJTs. At a given displacement dose, 10 MeV protons induce the maximum degradation of current gain of 2N2222 NPN BJTs, while 3 MeV protons cause the minimum degradation. In this case, non-ionizing energy loss (NIEL) methodology is not suitable to normalize the displacement damage induced by 3 MeV, 5 MeV and 10 MeV protons, which is attributed to the synergistic effect of ionization and displacement damage. The displacement defect centers in based-collector junction of 2N2222 transistor induced by 3 MeV, 5 MeV and 10 MeV proton exposures, were discovered and characterized by deep level transient spectroscopy (DLTS). Based on the comparison between the electrical parameters and the DLTS results, it is shown that, interface traps due to ionization damage induced by high-energy protons spread the emitter-base depletion layer, leading to the enhancement effects to displacement damage in the base-collector junction of NPN BJT. Meanwhile, bias voltage used during DLTS measurement influence characteristics of DLTS signals. With the increasing reverse bias, the value of $\Delta {\rm C}/{\rm C}$ for VO, ${{\rm V}_2}(= / -)$ , E4 and ${\rm V}_{2}(- /0) + {\rm E}5$ centers increases.

Phonon contribution to nonionizing energy loss in silicon detectors**Supported by National Natural Science Foundation of China (11175223, 11305231, 11205220)

Nonionizing energy loss (NIEL) has been applied to a number of studies concerning displacement damage effects in materials and devices. However, most studies consider only the contribution of displacement damage effects, neglecting the contribution from phonons. In this paper, a NIEL model, which considers the contribution of phonons, has been established using the Monte Carlo code SRIM. The maximum endurable fluence for silicon detectors has been estimated using the equivalent irradiation fluence compared with experimental data for the incident particles. NIEL is proportional to the equivalent irradiation fluence that the detector has received.

Displacement damage effect on the radiation induced deuterium absorption for different types of SiC

SiC-derived materials are primary candidates for FCI due to their excellent properties. During reactor operation the ceramic material will be exposed to tritium and also to a hostile radiation environment The two main aims of this work are first to compare different types of SiC in terms of radiation induced deuterium absorption and second to address the displacement damage effects. Thermo stimulated desorption (TSD) measurements were carried out for both electron irradiated and unirradiated samples in order to evaluate radiation enhanced deuterium retention. The amount of deuterium absorbed during irradiation strongly depends on the type of SiC material. To address the displacement damage effects the different types of SiC materials were subjected also to 45keV neon implantation in order to produce displacement damage. After being implanted the deuterium absorbed became very similar irrespectively to the type of SiC.

Stuck Bits Study in DDR3 SDRAMs Using 45-MeV Proton Beam

This work shares the observations of stuck bits by proton beam in DDR3 components in 3x-nm technologies. The DDR3 SDRAMs from four major DRAM manufacturers were tested with a 45-MeV proton beam at an operating frequency of 800 MHz. The beam exposure resulted in single bit upset (SBU) and multiple bit upsets (MBUs), as well as single and multiple stuck bits in a word due to micro-dose and displacement damage effects. The number of stuck bits reduced as the refresh interval duration was decreased. Moreover, for the tested samples, the stuck bits were recovered completely and could be run in the normal operation mode after annealing at $150^{\circ}{\rm C}$ . The occurrence of multiple stuck bits in a word was likely due to damages to the control logic and those stuck bits were recovered as well after annealing at $150^{\circ}{\rm C}$ .

Tritium Retention in Reduced-Activation Ferritic/Martensitic Steels

The effects of displacement damage, plasma exposure and heat loads on T retention in reduced-activation ferritic/martensitic (RAFM) steels were investigated by exposing the steels to DT gas at 473 K. Despite enormous change in surface morphology, T retention in the heat-loaded specimen was comparable with that in the unloaded specimen. The exposure to plasma resulted in a drastic increase in T retention at the surface and/or sub surface. However, the T trapped at the surface/subsurface was easily removed by maintaining the specimens in air at ~300 K. Formation of radiation-induced defects led to a significant increase in T retention, and T trapped in the defects was not removed at ~300 K. These observations suggest that displacement damages have the largest effects on T retention at ~473 K.

Dark signal degradation in proton-irradiated complementary metal oxide semiconductor active pixel sensor

In this paper, we discuss the dark signal increase in complementary metal oxide semiconductor (CMOS) active pixel sensor due to proton-induced damage, and present the basic mechanism that may cause failure. When the fluence of protons reaches a predetermined point, the change of dark signal of the device is measured offline. The experimental result shows that as the fluence of protons increases, mean dark signal increases rapidly. The main reason for dark signal degradation is: 1) the ionizing damage causes a build-up of oxide trapped charge and interface state at the Si-SiO2 interface. The creation of the interface traps (with energy levels within the silicon bandgap), which can communicate with carriers in the silicon, gives rise to the thermal generation of the electron-hole pairs and, hence increasing the dark signals; 2) when protons pass through the sensor, there is a possibility of collisions with silicon lattice atoms in the bulk silicon. In these collisions, atoms can be displaced from their lattice sites and defects are formed. These resulting defects can give rise to states with energy levels within the forbidden bandgap. The increasing of dark signal is therefore one of the prominent consequences of bulk displacement. We use multi-layered shielding simulation software to calculate the ionization damage dose and displacement damage dose. Based on the comparison of the test data of gamma radiation, combined with the device structure and process parameters, a theoretical model for separation proton-induced ionization and displacement damage effects on CMOS active pixel is constructed, and the degradation mechanism of the mean dark signal is investigated. The result shows that the contribution of ionization effect induced surface dark signal and the contribution of displacement damage induced bulk dark signal to dark signal degradation of the whole device are roughly equal in this domestic CMOS active pixel.

Evaluation of silicon tuning fork resonators under mechanical loads and space-relevant radiation conditions

This work reports on mechanical tests and irradiations made on silicon bulk-acoustic wave resonators. The resonators were based on a tuning fork geometry and actuated by a piezoelectric aluminum nitride layer. They had a resonance frequency of 150 kHz and a quality factor of about 20,000 under vacuum. The susceptibility of the devices to radiation-induced degradation was investigated using Co60γ-rays and 50 MeV protons with space-relevant doses of up to 170 krad. The performance of the devices after irradiation indicated a high tolerance to both ionizing damage and displacement damage effects. In addition, the device characteristics were evaluated after mechanical shock and vibration tests and only small effects on the devices were observed. In all experiments, no significant changes of the resonance characteristics were observed within the experimental uncertainty, which was below 100 ppm for the resonance frequency. The results support the efforts toward design and fabrication of highly reliable MEMS devices for space applications.