Radiation effects of 50-MeV protons on PNP bipolar junction transistors

The effects of radiation on 3 CG110 PNP bipolar junction transistors(BJTs)are characterized using 50-Me V protons,40-Me V Si ions,and 1-Me V electrons.In this paper,electrical characteristics and deep level transient spectroscopy(DLTS)are utilized to analyze radiation defects induced by ionization and displacement damage.The experimental results show a degradation of the current gain and an increase in the types of radiation defect with increasing fluences of 50-Me V protons.Moreover,by comparing the types of damage caused by different radiation sources,the characteristics of the radiation defects induced by irradiation show that 50-Me V proton irradiation can produce both ionization and displacement defects in the 3 CG110 PNP BJTs,in contrast to 40-Me V Si ions,which mainly generate displacement defects,and 1-Me V electrons,which mainly produce ionization defects.This work provides direct evidence of a synergistic effect between the ionization and displacement defects caused in PNP BJTs by 50-Me V protons.

Atomic Structure of the Pt Surface after Bombardment with Ar+ Ions (E ~ 30 keV)

The results of the modification of the atomic structure of the Pt surface after bombardment by accelerated beams of Ar+ ions are presented. Field ion microscopy was used to study the irradiated surface on an atomic scale. From the analysis of the ion contrast of the atomically clean surface of platinum after bombardment with Ar+, a large number of radiation defects of various types were found. Individual vacancies, interstitial atoms, Frenkel pairs, depleted zones, nanoclusters of displaced atoms, etc. have been registered. It has been established that the depth of the near-surface volume of the irradiated metal with defects (except for zero-dimensional defects) is 1 - 1.5 nm for the bombardment regime: F = 1016 ion/cm2 and E = 30 keV.

Evaluation of tungsten interatomic potentials for radiation damage simulations

The structure and properties of materials under neutron irradiation are an important basis in future fusion reactors.In the absence of fusion neutron sources for irradiation experiments,it is increasingly important and urgent to carry out neutron irradiation simulations on fusion reactor materials and then establish complete databases of defect properties and collisional cascades,where the first and foremost step is to select suitable interatomic potentials for atomistic-level simulations.In this work,six typic interatomic potentials for tungsten(W)are evaluated and reviewed systematically for radiation damage simulations.The relative lattice stability and elastic constants of bulk W are considered first with those potentials;then,the properties of point defects and defect clusters at interstitial sites and vacancies are obtained by molecular statics/dynam-ics simulations.The formation energies of interstitial/vacancy clusters,1/2<111>and<100>dislocation loops in W and the threshold displacement energies along different directions are also determined.In addition,the extended defects are further investigated,such as free surfaces and the energy profiles of 1/2<111>{110}and 1/2<111>{112}stacking faults.The current results provide a reference for selecting W potentials to simulate the radiation damage.

Unconventional energetics of small vacancy clusters in BCC high-entropy alloy Nb_(0.75)ZrTiV_(0.5)

The stability of small vacancy clusters including divacancy,trivacancy and tetravacancy has been studied in body-centered cubic high-entropy alloy Nb_(0.75)ZrTiV_(0.5) in structures of random solid solution and short-range order by first-principles calculations and molecular dynamics simulations.Different from conventional body-centered cubic metals,the tightly bound configurations have a lower structural stability and are not preferred energetically in the studied high-entropy alloy.Instability of vacancy configurations leads to vacancy-atom exchanges that favor less compact configurations.The formation energy of small vacancy clusters is much smaller than its constituent elements of Nb and V due to the large structural adjustment induced by severe local lattice distortion.The difference in local lattice distortion and elemental arrangement in the vacancy neighborhood leads to significant site-to-site variation in vacancy cluster energy and configuration.The formation energy has a strong correlation with the local energy state of the vacancy configuration and the extent of structural relaxation.Compared to random solid solution,the structure of short-range order has a higher stability for the most compact cluster configurations and tends to have higher vacancy cluster formation energy.According to classical molecular dynamics simulations of cluster diffusion at high temperature,the studied high-entropy alloy has a higher probability of cluster dissociation compared to Nb and V.The unconventional energetics of small vacancy clusters is expected to have a profound impact on their generation,diffusion,dissociation,coalescence,as well as the defect microstructure evolution during irradiation.