基于GEANT4模拟分析不同能量质子在CMOS APS中的位移损伤研究

本文针对图像传感器在空间辐射环境中电学性能退化问题,采用蒙特卡罗方法基于互补金属氧化物半导体（CMOS）APS器件建立几何模型,开展不同能量质子与靶原子的相互作用过程研究。通过研究不同能量质子辐照下初级碰撞原子的能谱分布及平均位移损伤能量沉积随质子能量的变化,讨论不同能量质子及空间站轨道质子能谱下在CMOS APS器件中位移损伤的差异。计算结果表明：随着入射质子能量的增大,辐照产生的初级碰撞原子的最大能量及核反应产生的初级碰撞原子（PKA）对位移损伤能量沉积的贡献逐步增加;对于大于1 MeV的质子辐照,CMOS APS器件中位移损伤研究可忽略氧化层的影响;不同能量的质子和CREME96程序中空间站轨道质子能谱下器件中位移损伤能量沉积分布结果显示,35 MeV质子与该空间站轨道质子能谱在器件敏感区中产生的总位移损伤能量沉积相近。该工作对模拟空间站轨道质子辐照下电子器件暗电流增长研究中辐照实验的能量选择,提供了参考依据。     

Void formation in solution-treated aisi 316 and 321 stainless steels under 46.5 mev ni6+ irradiation

The swelling and radiation damage structure developed in solution-treated 316 and 321 stainless steels bombarded by 46.5 MeV Ni⁶⁺ ions in the Variable Energy Cyclotron (VEC) have been determined. Foils were pre-injected with 10^?5 a/a He at room temperature and subsequently bombarded by Ni⁶⁺ ions in the temperature range 450–750°C at a damage rate of 1–3 × 10^?3 dpa per second to doses up to 300 dpa and specimens from the foils were examined by transmission electron microscopy. The data obtained were compared with data from other experiments aimed at simulating the fast-neutron irradiation of 316 and 321 steels, in particular previous work with 20 MeV C²⁺ ions and with data on fast-reactor bombarded material. The swelling rates in Ni-ion bombarded specimens were about a factor two less than those in C-ion bombarded specimens and in good agreement with swelling rates in 5 MeV Ni⁺- and neutron-bombarded material. The peak swelling temperature after a dose of 40 dpa was 650°C in 316 steel and 625°C in 321 steel where the swelling was about 5.8% and 4.6% respectively.     

Neutron Total Cross Section for Iron around Resonance Valley near 24 keV

A neutron leakage spectrum from a nickel sphere surrounding a 14-MeV neutron source is measured and analyzed in order to verify the accuracy of nickel cross sections. Measurement is done by means of a time-of-flight technique in the range of 2–15 MeV using an NE213 scintillator, and compared with calculations carried out with MCNP, a continuous energy Monte Carlo transport code, using JENDL-3PR1 and ENDFIB-IV neutron libraries.

In spite of an overestimation of neutron flux near 13 MeV, the calculated result employing JENDL-3PR1 shows generally better agreement with the measured spectrum. In ENDF/B-IV usage, there is disagreement between measured and calculated spectra between 5 and 12 MeV. Problems in evaluated nuclear data for nickel are also described.     

质子在氮化镓中产生位移损伤的Geant4模拟

材料受到辐照时产生的位移损伤会导致其微观结构发生变化,从而使其某些使用性能退化,影响其使用效率,减短其使用寿命。利用Geant4模拟了质子在氮化镓中的输运过程,计算了1、10、100、500 MeV能量质子入射氮化镓材料产生的初级撞出原子的种类、能量信息及离位原子数。获得了10 MeV质子产生的位移缺陷分布;计算了4种能量质子入射氮化镓材料产生的非电离能量损失(NIEL);研究了质子产生位移损伤过程的影响要素。研究发现,入射质子能量对其在材料中产生的初级撞出原子的种类、能量、离位原子数等信息有着非常大的影响;单位厚度所沉积NIEL随着入射质子能量的增大而减小;10 MeV质子入射氮化镓所产生的离位原子数随入射深度的增加而增加,但在超出其射程范围以外有一巨大回落;能量并不是影响质子与氮化镓靶材料相互作用的唯一因素。     

质子在砷化镓材料中产生位移损伤的Geant4模拟

本文使用Geant4模拟了1、5、10、20、50、100、500、1000 MeV能量的质子入射GaAs的位移损伤情况。随入射质子能量的增大,产生的初级离位原子（PKA）数目增加、种类增多;PKA能谱分布总体上呈递减趋势,PKA在低能量区间所占份额降低,在高能量区间所占份额升高。研究结果表明,辐射缺陷浓度在质子入射方向上遵循布拉格规律。     

Production of voids in nickel with high energy selenium ions

Irradiation of high purity (99.9 wt %) nickel at 525 °C with 6 to 11 MeV selenium ions produced voids in the metal. In general, the size and number density of the voids increased with displacement damage up to approximately 50 displacements per atom (dpa). Irradiation to higher displacement densities caused a slight reduction in the average size and a continued increase in the number density of voids. The resultant swelling was found to increase as the 1.45 power of the displaced atom density until approximately 50 dpa. The volume change appears to saturate at approximately 4–5% in the 100–400 dpa range. A face centered cubic superlattice of voids was discovered in nickel which had been irradiated to 400 dpa.     

Ion radiation damage in copper

Transmission electron microscopy techniques have been used to study dislocation loop type damage as a function of depth in copper single crystals irradiated with MeV Cu, Ni and He ions at room temperature. By comparing the location of the peak in the experimental depth profiles with calculated damage energy curves, the electronic stopping powers of Cu and Ni ions in copper were deduced. The deduced electronic stopping powers have been compared with those predicted by Lindhard et al., Bricc, and the Northcliffe and Schilling tables. It was found that the deduced stopping powers agreed well with the Northcliffe and Schilling values corrected for Z₂ oscillations by the method proposed by Ward et al. In the case of 1 MeV He ions, good agreement was obtained between the observed damage peak position and that calculated using the experimental electronic stopping of Ziegler and Chu and that of White and Mueller.     

Proton simulation of displacement effects induced in metals by 14 mev neutrons

In designing a D-T fusion reactor, one must know the effect of a high flux of 14 MeV neutrons on structural materials. Available laboratory sources of 14 MeV neutrons are not intense enough to expose samples to the expected flux. Bombardment with other particles is one way of simulating the anticipated neutron environment. The energy spectrum of atoms recoiling from collisions with bombarding particles can be calculated from elastic-scattering and nonelastic-reaction data for the incident species. This analysis shows that 16 MeV protons closely simulate the displacement effects caused by 14 MeV neutrons. In niobium the average atom recoiling from a 14 MeV neutron interaction has 65 keV of damage energy. The mean damage energy deposited per cm³ of niobium by a fluence of one 14 MeV neutron per cm² is 14 keV. The equivalent quantity for 16 MeV protons incident on niobium is 33 keV.     

Damage distributions in LiNbO3 crystal induced by MeV F tilted implantations

X-cut LiNbO₃ crystals have been implanted by 0.8, 1.0 and 1.2 MeV F⁺ tilted at angles of 15°, 45° and 60° with doses of 5 × 10¹⁴, 7 × 10¹⁴ and 5 × 10¹⁴ ions/cm², respectively. The Rutherford backscattering (RBS)/channeling technique was used to investigate the induced damage distributions. The damage profiles were deconvoluted from the measured spectra after considering the energy spread due to the different stopping power of channeled and nonchanneled ions. Good agreements were obtained between the measured damage profiles and the calculated defect profiles by TRIM'90 (transport of ions in matter, version 1990), except that the measured damage concentration was enhanced in the near-surface region. Information on the lateral and longitudinal damage spread in LiNbO₃ crystals was obtained from the damage profiles induced by tilted ion implantations and compared with TRIM'90 calculation.     

Separation of protactinium in the reaction of 60 MeV／nucleon ^18O ions with natural uranium

The activities of protactinium were produced by the multi-nucleon transfer reactions in bombardment of the natural uranium with 60 MeV/nucleon ^18O ions.A simple,relatively fast radiochemical procedure was used for extraction separation of protactinium from the uranium and a variety of reaction products using 1-phenyl-3-methyl-4-benzyoyl-5-pyrazolone and tri-sio-octylamine as extractants.The γ ray spectrum of the separated protactinium fractions showed that the protactinium could be separated from all of the amin impurity elements.The decontamination factors of the uranium and the main reacion products produced in the reaction are given.     

Re-evaluation of neutron displacement cross sections for silicon carbide by a Monte Carlo approach

Neutron displacement cross sections for SiC are re-evaluated by a Monte Carlo approach, with damage energies of primary recoils calculated by the stopping and range of ions in matter (SRIM) code. The validity of the Monte Carlo model is examined by the case of iron, and the results show good agreement with the reference values. Neutron displacement cross sections for SiC at energies up to 100 MeV are calculated, and averaged over the neutron spectra of a fusion DEMO reactor, the high flux test module of the International Fusion Materials Irradiation Facility, and typical fission test reactors. Gas production is also calculated for those neutron irradiation facilities. Finally, the suitability of the displacement cross sections is discussed. The results on comparison among neutron irradiation of different facilities by the current displacement cross sections are similar to those by results of the previous work. Moreover, since neutron displacement cross sections in this study are calculated with damage energies of primary recoils calculated by SRIM, neutron damage evaluated by our displacement cross sections is suitable for correlation with damage by heavy ions calculated by SRIM.     

Radiation enhanced diffusion of implanted platinum in silicon guided by helium co-implantation for arbitrary control of platinum profile

The in-diffusion of platinum into a low-doped n-type float zone silicon guided and enhanced by radiation damage produced by co-implantation of helium ions was investigated. The implantation of 1 MeV platinum ions at different doses ranging from 5 × 10¹¹ to 5 × 10¹² cm⁻² was used to produce a finite source for platinum diffusion. Single and multiple energy implantation of helium ions with energies 7, 9, 11 and 13 MeV introducing different profiles of radiation defects were applied to enhance and shape the diffusion of platinum atoms performed by 20 min annealing at 725 °C in vacuum. The distribution of in-diffused platinum was studied by monitoring the acceptor level of substitutional platinum (E_C − E_T = 0.23 eV) by deep level transient spectroscopy. Results show that the helium co-implantation significantly enhances platinum diffusion and allows its control up to the depths of hundreds of micrometers. The resulting Pt_s distribution is given by the profile of radiation damage produced by helium ions while the amount of in-diffused Pt_s can be controlled by the dose of platinum implantation. It is also shown that an extra annealing at 685 °C performed prior to helium implantation substantially increases the amount of in-diffused platinum.     

Suppression of sputtering of nickel by coverage with self-sustaining thin segregated carbon layers

Sputtering of two-layered films composed of nickel (~5000 Å) and nickel carbide (~1500 Å) at 600° C by 5 keV Ar⁺ bombardment on the nickel side has been studied using Rutherford backscattering of 1.3 MeV H⁺ ions. It is found that the removal rate of nickel atoms from specimens is dependent on ion current density and that the removal rate of nickel atoms is very much smaller than that of carbon atoms when the ion current density is low. During ion bombardments at a low current density carbon segregation by a thickness of nearly two monolayers is observed at the nickel surface. Thus suppression of the removal rate of nickel atoms is ascribed to coverage of the nickel surface with segregated carbon atoms which are continuously supplied by diffusion through the nickel film from the carbide layer.     

Study on preventing segregation of erbium atoms to a silicon surface by annealing in oxygen atmosphere at high temperature

The damage produced by implantation of Er ions of 400 keV at a fluence of 5 × 10¹⁵ ions/cm² in silicon was investigated by Rutherford backscattering spectrometry with 2.1 MeV He²⁺ ions with multiple scattering models. It was found that the damage around the Si surface was almost removed after annealing in oxygen and nitrogen atmospheres successively at 1000 °C, and only a small portion of the Er atoms segregated to the silicon surface. Most of the Er atoms diffused to deeper depths because of the affinity of Er for oxygen.     

Subject index

Resistivity damage rates as a function of ion penetration depth were measured for 2.7 to 5.4 MeV Al ions in aluminium. These damage rates accurately scale with damage energy calculations for a large fraction of the range of the ions, but are ~14% low in the region of the maxima in the damage curves. This difference in the peak region was related to changes in the damage efficiency expected from differences in the recoil spectra in the peak region compared to the incident beam. Deviation from the LSS velocity proportional electronic stopping was indicated by these experiments and an improved agreement between experiment and calculations was obtained by adjustment of the parameters in the Brice formula for the electronic stopping cross section. The fission spectrum neutron damage production rate in aluminum was measured and compared with the ion damage rates. The damage efficiency of the neutron damage is in agreement with the ion damage efficiencies within ~8%.     

High energy electron induced displacement damage in silicon

New measurements of displacement damage factors for electron-irradiated (4 to 53 MeV) bipolar silicon transistors have extended the correlation between nonionizing energy loss and damage factors reported previously another three orders of magnitude downward, to cover a total of six decades. To first order, the correlation remains linear for both n- and p-type silicon, but deviations are observed and explained in terms of differences in the fraction of initial vacancy interstitial pairs that recombines. These differences correlate linearly with the low-energy component of the PKA spectrum. Deep level transient spectroscopy measurements show oxygen- and dopant-related defect levels as well as divacancies. Defect concentrations scaled linearly with gain degradation, and no differences were seen between electron and proton plus neutron irradiated material. The results are consistent with a damage mechanism involving migration of vacancies to form well-separated stable defects     

Mixed Ne/Ni beams for radiation damage studies on the harwell variable-energy cyclotron

Ion irradiation facilities which use metal ions beams concurrently with beams of He or He+H have been developed extensively in recent years for the simulation of radiation effects which occur in metals during neutron irradiation in fission or fusion reactors. Helium ions are considered necessary to simulate the effect of helium on cavity nucleation and the metal atom is used to create an adequate atomic displacement rate. Many of these dual-beam facilities require the provision of two accelerators, one to produce a gas atom and the other a metal atom beam, and commonly employ low-energy metal ions (eg. 4 MeV ⁵⁸Ni⁺) which have a limited range (0.75 μm) in metals of practical interest. Damage can be created at greater depths by use of high energy ions (eg 45 MeV ⁵⁸Ni) in a cyclotron, but charge-to-mass constraints make it difficult to produce a mixed beam of concurrent He and metal ions. It is noted that the heavier inert gas atom neon has similarities in atomistic behaviour in metals to those of helium and could possibly be used as an analogue for helium. In this report we consider this aspect and show than by suitable matching of $\text{e}\text{m}$ ratio a mixed beam of 15 MeV ²⁰Ne²⁺ and 45 MeV ⁶⁰Ni⁶⁺ can be obtained from the Harwell VEC with gas/metal atom ratios and beam currents that are suitable for use in radiation damage simulation experiments in metals. It is proposed that exploratory studies should be carried out with mixed Ne/Ni beams into nickel to investigate the possibility of using neon as an analogue for helium in radiation damage simulation studies.     

Second phase formation at microvoids and gas atom entrapment at fusion reactor first wall surfaces

Results of cascade production and annealing studies for iron are projected to the currently considered fusion reactor first wall materials. Collision cascades initiated by primary knock-on atoms (PKA) with energies above 50 keV, in iron, separate into distinct subregions. Most PKA produced during fission reactor neutron irradiation have energies below 50 keV, but the energies of PKA produced by 14.1 MeV neutron irradiation commonly lie in the 50–500 keV range in iron and vanadium alloys. Computer experiment simulation indicates that, when present, carbon, silicon, and nitrogen, freed by irradiation from bulk precipitates, should tend to re-precipitate on the facets of microvoids which form in cascade subregions during short-term annealing.     

Nickel-ion bombardment of annealed and cold-worked type 316 stainless steel

Bombardment with high doses of 5 MeV nickel ions has produced swellings as high as 90% and 60%, respectively, in annealed and 20% cold-rolled Type 316 steels. The steels contained 15 ppm of cyclotron-injected helium. Swellings were determined by both transmission electron microscopy and by a step-height method that measures the total swelling integrated along the ion path. The swelling in annealed Type 316 has a pronounced peak in the vicinity of 625°C, which is about 155°C higher than the peak swelling temperature in-reactor. The magnitudes of the swelling, void densities and void sizes produced in annealed Type 316 by nickel ions and in-reactor at the respective peak swelling temperatures are similar and it is concluded that the nickel ion bombardments provide an acceptable simulation of in-reactor behavior. Using the high dose ion results to guide extrapolation of presently available EBR-II data to higher fluences leads to the prediction that the swelling of annealed Type 316 steel at the peak swelling temperature will reach 40% at $\text{2 × 10}{}^{\mathrm{p23}}\text{n/cm}{}^2\text{(E > 0.1 MeV)}$ in EBR-II core, and 70% at $\text{3 × 10}{}^{23}\text{n/cm}{}^2$. These fluences in EBR-II correspond to 155 and 230 dpa respectively. Twenty percent reduction by cold-rolling reduces the ion produced swelling by 35% at 625°C and by 50% at 575°C.