Kinchin-Pease Model Research Articles

Effect of Stress on Irradiation Responses of Highly Oriented Pyrolytic Graphite.

The effect of stress on irradiation responses of highly oriented pyrolytic graphite (HOPG) was studied by combing molecular dynamics (MD) simulation, proton irradiation, and Raman characterization. MD simulations of carbon knock-on at energies < 60 eV were used to obtain average threshold displacement energies () as a function of strain ranging from 0 to 10%. Simulations at a higher irradiation energy of 2–5 keV were used to study the effect of strain on damage cascade evolution. With increasing tensile strain, was reduced from 35 eV at 0% strain to 31 eV at 10% strain. The strain-reduced led to a higher damage peak and more surviving defects (up to 1 ps). Furthermore, high strains induced local cleavage around the cavities, as one additional mechanism of damage enhancement. Experimentally, HOPG film was folded, and the folded region with the maximum tensile stress was irradiated by a 2 MeV proton beam. Raman characterization showed significantly enhanced D to G modes in comparison to the stress-free irradiation. Based on the strain dependence of and the Kinchin–Pease model, a formula for displacement estimation under different tensile strains is proposed. The stress effects need to be considered in graphite applications in a reactor’s harsh environment where both neutron damage and stress are present.

PKA distributions in InAlAs and InGaAs materials irradiated by protons with different energies

In this paper, the Primary Knock-on Atoms (PKAs) density and energy distributions in InAlAs and InGaAs materials have been analyzed by an energy stopping power improved Monte Carlo (MC) method under proton-radiation with energies of 25 keV, 50 keV, 100 keV, and 150 keV. The results show that in the initial incident stage of protons, the electronic energy loss density is 2–3 orders of magnitude higher than the nuclear energy loss density, afterwards, the injected protons accelerate to deposit more energy and finally stop in the target, producing a large number of PKAs. The injected proton density, PKA density and PKA energy density almost follow a Bragg-shape distribution. With the increase of irradiation energy, their peak-positions shift toward deeper direction with peak values decrease gradually, and moreover, the PKA peaks are always shallower than the irradiated protons. In addition, Frenkel Pairs generation rate has been calculated based on Kinchin-Pease (K-P) model modified by Ziegler, which decreases as proton energy increases because of the reduction of scattering cross section. The verification of this method combines both SRIM 2013 and Northcliffe experimental data and the results have shown compatible trends.

An analysis of defects induced by high dose γ-ray irradiation and their influence on the charge transport properties in CdZnTe detectors

Radiation damage effects were important issues for the development of CdZnTe detectors in space-exploration field applications. In this study, we explored the radiation damage mechanisms on CdZnTe crystals based on the Kinchin-Pease model. The type and evolution of irradiation induced defects under different gamma ray doses were investigated by the photoluminescent technique. Laser beam induced transient current measurement was applied to investigate the influence of defects on the charge transport property. Our results demonstrated that the radiation induced defects accumulated negative space charges, which significantly distorted the electric field distribution and reduced electron mobility by enhancing the ionized impurities scattering effect. By correlating the results with 241Am gamma ray radiation response spectra measurement, the effects of radiation damage on the detector performance were discussed.

Simulating radiation damage cascades in graphite

Molecular dynamics simulation is used to study radiation damage cascades in graphite. High statistical precision is obtained by sampling a wide energy range (100–2500eV) and a large number of initial directions of the primary knock-on atom. Chemical bonding is described using the Environment Dependent Interaction Potential for carbon. Graphite is found to exhibit a radiation response distinct from metals and oxides primarily due to the absence of a thermal spike which results in point defects and disconnected regions of damage. Other unique attributes include exceedingly short cascade lifetimes and fractal-like atomic trajectories. Unusually for a solid, the binary collision approximation is useful across a wide energy range, and as a consequence residual damage is consistent with the Kinchin–Pease model. The simulations are in agreement with known experimental data and help to clarify substantial uncertainty in the literature regarding the extent of the cascade and the associated damage.

Medium energy ion scattering analysis of the evolution and annealing of damage and associated dopant redistribution of ultra shallow implants in Si

As junction depths in advanced semiconductor devices move to below 20 nm, the process of disorder evolution during ion implantation at ultra low energies becomes increasingly influenced by the surface. This may also hold for shallow regrowth and dopant redistribution processes during subsequent thermal annealing of the substrate. The investigation of these near-surface processes requires analytical techniques with a depth resolution of≤1 nm. Medium energy ion scattering (MEIS) has the unique capability of simultaneously providing quantitative, high-resolution depth distributions of implant disorder (displaced Si lattice atoms) and of implanted atoms, albeit not of light species. We report here a comparative MEIS investigation into the growth mode of shallow disordered/amorphised layers during≤1 keV B+ and 2.5 keV As+ ion implantation into Si. In both cases the growth of the damage depth profiles differs significantly from the energy deposition function, as it is strongly determined on the one hand by the proximity of the surface acting as a nucleation site for migrating point defects formed during implantation, which results in planar growth of the amorphous layer, and on the other by the dynamic annealing processes operating at room temperature. When such defect recombination processes are inhibited, e.g. for low dose, ultra shallow 200 eV B+ implants, MEIS shows that defect production yields exceeding the Kinchin–Pease model predictions are achieved. For As implants, a correlation is observed between the movement of the As and the depth of the growing, planar amorphous layer. Thermal annealing of As implanted samples at different temperatures and durations leads to solid phase epitaxial regrowth. During regrowth, MEIS shows that there is a close correlation between damage dissolution, the movement of nearly half of the As dopant into substitutional sites and the snowploughing of a fraction of the As in front of the advancing amorphous/crystalline interface leading to the formation of a less than 1 nm wide As pile-up layer trapped under the oxide.

Proton Irradiation Effects on Dielectric Coatings on Optics

Radiation damage on dielectric thin-layer was studied. The dielectric multilayer coating is a promising technology for the use of solar light collection optics in Space Solar Power System (SSPS) in the geostationary orbit. We estimated spatial distributions of numbers of displacement atoms using a Kinchin-Pease model for the proton incidence, and Frenkel pairs created via self-trapped exciton process initiated by electron excitation in the target for the proton and electron incidences. Proton incidence gives damages near the surface of the target due to low energy protons dominating its energy spectrum. Proton irradiation experiment for a thin layer of several dielectric targets shows toughness for about 10-year-equivalent exposure time at geostationary orbit.

A study of ion implantation into crystalline germanium

We report an experimental and simulation study for introducing dopant ions into (1 0 0) germanium in the energy range from 5 to 40 keV. The successful calibration of our Monte Carlo ion implantation simulator for amorphous and crystalline Ge targets is demonstrated by comparison of predicted boron profiles with SIMS data. The implantation profile in Ge is shallower than in Si for a given energy due to the larger nuclear and electronic stopping power of Ge atoms. The generated point defects and amorphized regions in the crystal are calculated by a modified Kinchin–Pease model. We found that the higher displacement energy in Ge, the stronger backscattering effect, and the smaller energy transfer from the ion to the primary recoil of a cascade are mainly responsible for the significantly reduced implantation damage in Ge. The point responses for boron implantations in Si and Ge are compared with each other. Finally the simulation results for the formation of interdigitated Ge-on-Si PIN-photodiodes are presented.

Dose-rate and temperature dependent statistical damage accumulation model for ion implantation into silicon

Currently there are extensive atomistic studies that model some characteristics of the damage buildup due to ion irradiation (e.g. L. Pelaz et al., Appl. Phys. Lett. 82 (2003) 2038–2040). Our interest is to develop a novel statistical damage buildup model for our BCA ion implant simulator (IIS) code in order to extend its ranges of applicability. The model takes into account the abrupt regime of the crystal-amorphous transition. It works with different temperatures and dose-rates and also models the transition temperature. We have tested it with some projectiles (Ge, P) implanted into silicon. In this work we describe the new statistical damage accumulation model based on the modified Kinchin–Pease model. The results obtained have been compared with existing experimental results.

Damage profiles of ultrashallow B implants in Si and the Kinchin-Pease relationship

Damage distributions resulting from 0.1–2keV B+ implantation at room temperature into Si(100) to doses ranging from 1×1014 to 2×1016cm−2 have been determined using high-depth-resolution medium-energy-ion scattering in the double alignment mode. For all B+ doses and energies investigated a 3–4nm deep, near-surface damage peak was observed while for energies at and above 1keV, a second damage peak developed beyond the mean projected B+ ion range of 5.3nm. This dual damage peak structure is due to dynamic annealing processes. For the near-surface peak it is observed that, at the lowest implant energies and doses used, for which recombination processes are suppressed due to the proximity of the surface capturing interstitials, the value of the damage production yield for low-mass B+ ions is equal or greater than the modified Kinchin-Pease model predictions [G. H. Kinchin and R. S. Pease, Rep. Prog. Phys. 18, 1 (1955); G. H. Kinchin and R. S. Pease, J. Nucl. Energy 1, 200 (1955); P. Sigmund, Appl. Phys. Lett. 14, 114 (1969)].

Calculation of Gamma Induced Displacement Cross-sections of Iron Considering Positron Contribution and Using Standard Damage Model

The displacement cross-section of iron was calculated for gamma-ray irradiation with the energy range of 1 to 15 MeV, which corresponds to radiation fields in fission reactors. Three gamma-material interactions, Compton scattering, pair production and photoelectric effect were considered. The displacements induced by both electrons and positrons were included. For damage function the modified Kinchin-Pease model with the displacement energy of 40 eV was applied, which are used as the standard damage model in neutron-induced displacement calculations. The standard damage model gave a lower cross-section by a factor of 1.3 compared to Kinchin-Pease model, and the exact treatment of positron contribution gave a lower cross-section by a factor 1.1 compared to an approximation treating positrons as electrons. The present cross-section was lower by a factor of 1.1–2.0 than the cross-sections previously proposed in the literatures.

Enhanced modelization of ion implant simulation in compound semiconductors

An efficient binary collision approximation ion implant code with enhanced prediction capabilities is presented. It includes recent improvements in physical models for compound semiconductors. It uses only one fitting parameter for low dose implantations. A periodic ab initio full bond electron density for the target is used. Damage accumulation is supported using a modified Kinchin–Pease model. To speed-up the code a refined algorithm for statistical noise reduction is also included in a three-dimensional case, including the lateral and shallow zones. The agreement with experiments is good for different target materials. A comparison with experimental SIMS results for several projectiles and targets is presented.

Improved binary collision approximation ion implant simulators

An efficient binary collision approximation (BCA) ion implant code with good prediction capabilities for semiconductor materials (Si, GaAs, SiC) with only one fitting parameter for low implantation doses is presented. It includes specific interatomic potentials and recent improvements in physical models for inelastic stopping. A periodic ab initio full bond electron density for the target is used. Damage accumulation is supported using a modified Kinchin–Pease model [G. H. Kinchin and R. S. Pease, Rep. Prog. Phys. 18, 1 (1955)]. Also, some of the BCA integration algorithms and target selection procedure have been refined. An algorithm commonly used for statistical noise reduction has been modified to also improve the noise reduction in the lateral and shallow zones. The agreement with experiments is good, even under channeling conditions and for different target materials. A comparison with experimental secondary ion mass spectroscopy results for several projectiles and targets is presented.

The Molecular Dynamics Study for the Damage and Etching Properties of Low Energy Ar Ion Implantation. (Effect of Ion Energy, Polar Angle of the Incident Ion and Substrate Strain).

Molecular dynamics simulations have been performed for the Ar bombardment to Si surface in order to investigate the damage and etching properties. The dependence of the ion energy, the polar angle of the ion and substrate strain was investigated. The averaged number of interstitials was found to be a linear function of the damage energy, and its slope showed good agreement with the Kinchin-Pease model. The averaged number of etched atoms was not linear and its efficiency decreased as the ion energy was increased. It was found that the damages and etchings were caused by the energy injection to the substrate inside and the instantaneous thermal spike of the substrate surface, respectively. Mixing of two types of collision, i.e. binary and many body collisions resulted in increased dispersion of the damage. The damage decreased as the polar angle was increased. Conversely the etching increased, and had the maximum value at 70 degree. The strain dependence showed the symmetrical increased curve both in tension and compression. However, under 10% compressive strain and 1000 eV ion energy, the blocking and instability of the lattice created the significant disorder region.

A molecular dynamics study of defect production due to low-energy collisions

Molecular dynamics (MD) simulations of collision cascades were studied in order to understand the effect of energy, temperature and direction of the primary knock-on atom (PKA) on the defect production in single crystal silicon for low-energy collision events. MD simulations were performed with ion energies ranging from 100 eV to 1 keV where the PKA was directed along the three major crystallographic directions at 0, 300 and 600 K. Collision cascades resulting from PKA energies above 100 eV appeared to undergo a solid- to liquid-like transformation at the height of the cascade event. Upon cooling, the liquid-like regions collapse resulting in the formation of numerous isolated defects and clusters of defects. We found that bulk and near-surface collision events followed the modified Kinchin-Pease model for defect production in silicon for the energies studied. Minimal temperature dependence was found for collision events that occurred in the bulk of the silicon crystal within the first 10 ps of the simulation.

Precipitation of copper in iron under swift ion irradiations

After irradiation was carried out on the Fe1.34 at% Cu supersaturated solution with 2.5 MeV electrons and 188 MeV oxygen ions at 290°C, we report new results about copper precipitation under 5.07 GeV krypton irradiation. The precipitation observed on line by electrical resistivity and after irradiation by tomographic atom probe experiments and microhardness measurements, shows that the kinetics of copper precipitation (in term of dpa calculated using the modified Kinchin–Pease model) is hundred times larger with GeV krypton ions than with MeV electrons and is the same under oxygen and electron irradiations. We show that such a behaviour can be explained only by assuming that the energy deposited in electronic excitations along the path of swift ions is actually able to induce precipitation in metallic supersaturated solid solutions.

Effects of micro-beam induced damage on single-event current measurements

Radiation damage introduced by the impact of heavy-ion micro-beams has been studied in connection with its effects on single-event transient currents, which are measured by the digitizing sampling method combined with focused ion micro-beams. It is found that the single-event currents decrease with increasing the repetition number of measurements and that there exists a linear relationship between the ion fluence and the reciprocal of the normalized single-event charge. A single-event damage equation is deduced, where the damage constant is proportional to the defect density calculated using either the Kinchin-Pease model or the TRIM code. Experimental techniques are developed to eliminate the effect of radiation damage.

Modeling of electronic stopping and damage accumulation during arsenic implantation in silicon

Arsenic implantation profiles in (100), (110) and (111) silicon at 150 keV with doses between 10 12 and 2.5 × 10 14cm −2 are presented. The implantations have been performed in [100], [110] and [111] channeling directions and in the case of (100) silicon also in random direction with a tilt angle of 7° from [100]. These data are used for the modeling of electronic stopping and damage accumulation. The electronic stopping model contains a nonlocal, free flight path dependent and a local, impact parameter dependent part. The parameters of the model are determined by considering the [100] and the [110] channeling implantations. For the description of damage accumulation a model based on the modified Kinchin-Pease model is used. It is shown that consideration of the finite recoil range is of minor importance for the prediction of implantation profiles. The [110] channeling implantation profile is used to determine the parameters of the damage accumulation model. The implantations in [111] and 7° from [100] direction and further experiments from the literature are simulated with the previously determined parameters for electronic stopping and damage accumulation. Excellent agreement is found, showing that the dependence of arsenic implantation profiles on energy, beam orientation and dose is correctly predicted.

Single-event current transients induced by high energy ion microbeams

Focused high-energy ion microbeams were applied to the study of the basic mechanisms of single-event upset. Waveforms of the current transients induced by He-, C-, O- and Fe-ion strikes on silicon diodes were measured by applying extremely low beam currents of an order of 10 fA and a wide-bandwidth digitizing sampling technique. Total collected charges are evaluated from the transient currents as a function of LET (linear energy transfer), bias voltage, and doping level, and are compared with theoretical values calculated using conventional single-event models. It is found that irradiation effects on the total collected charges can be explained by the introduction of displacement atoms calculated using Coulomb potential and the Kinchin-Pease model.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Computer simulations of radiation damage in amorphous solids.

Microscopic radiation damage in a Lennard-Jones amorphous solid is investigated by computer simulations of collision cascades. Molecular-dynamics simulations with various primary knock-on atom (PKA) energies and directions are carried out. Energy outflow from the computational box is accounted for but electronic losses are neglected. The simulations show the PKA energy to spread rapidly among the nearby atoms, and the atomic trajectories disclose such features as replacement collision sequences and focused chains. Vacancies are created in the central region of the cascade and are surrounded by a cloud of interstitials. The defects mainly disappear independently of each other, the vacancies faster than the interstitials. Recombination plays a minor role. At the end of a simulation all the defects created have vanished and little change in the sample volume or structure is observed. The threshold energy for a permanent displacement is found for various PKA directions. The validity of the modified Kinchin-Pease model for an amorphous solid is discussed.

Thermal Spike Related Nonlinear Effects in Ion Beam Mixing at Low Temperatures

ABSTRACTA semi-empirical model for ion mixing at low temperatures was developed taking into account collisional mixing and thermal spike effects, as well as the thermal spike shape. The collisional mixing part was accounted for by the Kinchin-Pease model, or, alternatively dynamic Monte Carlo simulation. For the thermal spike, the ion beam mixing parameter Dt/Φ is derived as being proportional to χ2+μ, where the damage parameter is defined as, χ = − F0/ΔHcoh, F0 is the damage energy deposited per unit path length, and μ is a constant dependent on the thermal spike shape and point defect density in the thermal spike regions. The shape of the thermal spike that best fit the experimental results depends on the magnitude of the cascade density. For relatively high density collisional cascades, where thermal spikes start to be important, it was found that a spherical thermal spike model was more consistent with experimental measurements at low temperatures. However, for extremely high density collisional cascade regions, a cylindrical thermal spike gave better results. Finally, three different regions of ion beam induced mixing were recognized according to different density levels of damage energy scaled by the damage parameter χ.