Electronic Stopping Power Model Research Articles

Nonadiabatic energy transfer in single wall carbon nanotube upon H+ irradiation from time-dependent density-functional theory

Accurate calculations of electronic stopping power (ESP) are critical to understanding ion–solid interactions for charged particle slowing down in materials. Basing on the nonadiabatic results from the time-dependent density-functional theory (TDDFT) for H ion intruding through single wall carbon nanotubes, we analyze and quantify the strength of the ion–solid interaction by tracking the momentum of the target atom. The slow-moving H is subjected to a friction force when the ion–solid interaction is weak. When the interaction is strong, the electrons in tube are excited and the coulomb repulsion between H ion and target atoms gradually dominates. A piecewise fitting physical model for ESP as a function of the impact parameter is built to show the dependency of ESP on impact parameters. These results explain energy loss of charged particles in matter at high-speed or large off-channel condition and provide a basis for understanding ion–solid interactions in more complex systems.

Development of an electronic stopping power model based on deep learning and its application in ion range prediction

Deep learning algorithm emerges as a new method to take the raw features from large dataset and mine their deep implicit relations, which is promising for solving traditional physical challenges. A particularly intricate and difficult challenge is the energy loss mechanism of energetic ions in solid, where accurate prediction of stopping power is a long-time problem. In this work, we develop a deep-learning-based stopping power model with high overall accuracy, and overcome the long-standing deficiency of the existing classical models by improving the predictive accuracy of stopping power for ultra-heavy ion with low energy, and the corresponding projected range. This electronic stopping power model, based on deep learning algorithm, could be hopefully applied for the study of ion-solid interaction mechanism and enormous relevant applications.

Monte Carlo Simulation of Ion Implantation in Crystalline SiC With Arbitrary Polytypes

A Monte Carlo model for ion implantation in crystalline SiC is developed, which can be applied to arbitrary polytypes, including but not limited to 2H-SiC, 3C-SiC, 4H-SiC, 6H-SiC, and 15R-SiC. It is shown that with optimized parameters, a semiempirical electronic stopping power model is effective in simulating the dopant profiles in both channeling and random direction implants, despite its highly anisotropic crystal structure of SiC. The effect of polytypism on the dopant profiles is also shown. The simulated dopant profiles are compared with the experimental SIMS profiles in 4H-SiC and 6H-SiC, and good agreement is obtained in both cases. Finally, the predicted dopant profiles in 15R-SiC are explored for the first time.

Molecular dynamics simulation of ion implantation into hafnium dioxide

The molecular dynamics (MD) method, with David Cai’s electronic stopping power model applied, is successfully applied to simulate implantation into HfO2. For the first time, a reliable fitting value of the single electron radius in the electronic stopping power model is given for boron, arsenic and phosphorus implantation into HfO2. Excellent agreement between simulation results and SIMS data has been obtained over the energy range of 3–40 keV using the derived fitting value. Our simulation results are found to be in better agreement with the SIMS data than those obtained by means of the traditional simulator TSUPREM4.

Molecular dynamics simulation of ion implantation into hafnium dioxide

The molecular dynamics (MD) method, with David Cai’s electronic stopping power model applied, is successfully applied to simulate implantation into HfO2. For the first time, a reliable fitting value of the single electron radius in the electronic stopping power model is given for boron, arsenic and phosphorus implantation into HfO2. Excellent agreement between simulation results and SIMS data has been obtained over the energy range of 3–40keV using the derived fitting value. Our simulation results are found to be in better agreement with the SIMS data than those obtained by means of the traditional simulator TSUPREM4.

Predictive Monte Carlo ion implantation simulator from sub-keV to above 10 MeV

In this paper is reported a general and accurate binary-collision-approximation- (BCA-)based Monte Carlo ion implantation model for implants into crystalline silicon. The combination of an improved semiempirical electronic stopping power model and Ziegler-Biersack-Littmark universal potential enables us to simulate a wide variety of implant species with only two different electronic stopping parameters for different implant species. With the model parameters fixed for a given implant species, excellent agreement is found with experimental secondary ion mass spectroscopy data for the energy range from sub-keV to above 10 MeV, and for different implant directions including random equivalent orientation, 〈100〉, 〈111〉, and 〈110〉 channeling directions. When compared with other BCA-based Monte Carlo simulators, it is demonstrated that more accurate results can be obtained for ultralow energy and very high energy implants. Furthermore, it is shown that, while the existing ion implantation simulators with the electronic stopping power based on the effective charge theory fail to predict the long tails of the deeply channeled implant species (such as Al), our model can predict these long tails successfully. Finally, an efficient damage model is also presented, which requires only one additional free parameter to accurately account for the damage accumulation and dechanneling effect. For high dose implants, substantial speed improvement over MARLOWE-based Monte Carlo simulators is observed.

Characteristics of sub-keV atom-Si(111) surface collisions

Molecular-dynamics (MD) simulations, using the potential developed by Tersoff, are reported for Si bombardment of Si(111) in the collisional energy range 15{endash}520 eV. A comparison between ordinary MD and a modified version that includes a model for electronic stopping power and electron-phonon coupling is made. It is found that such modification does not significantly change the results for penetration depth and surface damage. However, electronic stopping does lead to energy dissipation and approximately 10{endash}15{percent} of the collisional energy is transferred to the electrons. The surface damage reaches deeper than the penetration of the projectile and is identified as single atom displacements or small-sized amorphous regions. {copyright} {ital 1999} {ital The American Physical Society}

Electronic stopping power for Monte Carlo simulation of ion implantation into SiC

A new electronic stopping power model for Monte Carlo simulation of ion implantation into 6H–SiC is presented. This model is based on the nonlinear density functional approach of Echenique et al. for the energy loss of slow ions moving through an electron gas and the ab initio pseudopotential calculations of Park et al. for the map of valence electrons of 6H–SiC crystal. A modified linear response theory has been used to treat the core electrons stopping. This model does not need fitting parameters and allows to fit the experimental distributions of implanted dopants in SiC both the peak region and the channeling tail of the SIMS profiles.

Simulation of Phosphorus Implantation into Silicon with a Single Parameter Electronic Stopping Power Model

We simulate dopant profiles for phosphorus implantation into silicon using a new model for electronic stopping power. In this model, the electronic stopping power is factorized into a globally averaged effective charge [Formula: see text], and a local charge density dependent electronic stopping power for a proton. There is only a single adjustable parameter in the model, namely the one electron radius [Formula: see text] which controls [Formula: see text]. By fine tuning this parameter, we obtain excellent agreement between simulated dopant profiles and the SIMS data over a wide range of energies for the channeling case. Our work provides a further example of implant species, in addition to boron and arsenic, to verify the validity of the electronic stopping power model and to illustrate its generality for studies of physical processes involving electronic stopping.

Phenomenological electronic stopping-power model for molecular dynamics and Monte Carlo simulation of ion implantation into silicon

It is crucial to have a good phenomenological model of electronic stopping power for modeling the physics of ion implantation into crystalline silicon. In the spirit of the Brandt-Kitagawa effective charge theory, we develop a model for electronic stopping power for an ion, which can be factorized into (i) a globally averaged effective charge taking into account effects of close and distant collisions by target electrons with the ion, and (ii) a local charge density dependent electronic stopping power for a proton. This phenomenological model is implemented into both molecular dynamics and Monte Carlo simulations. There is only one free parameter in the model, namely, the one electron radius rs0 for unbound electrons. By fine tuning this parameter, it is shown that the model can work successfully for both boron and arsenic implants. We report that the results of the dopant profile simulation for both species are in excellent agreement with the experimental profiles measured by secondary-ion mass spectrometry(SIMS) over a wide range of energies and with different incident directions. We point out that the model has wide applicability, for it captures the correct physics of electronic stopping in ion implantation. This model also provides a good physically-based damping mechanism for molecular dynamics simulations in the electronic stopping power regime, as evidenced by the striking agreement of dopant profiles calculated in our molecular dynamics simulations with the SIMS data.

An Electronic Stopping Power Model in Single-Crystal Silicon From a Few KeV to Several MeV

AbstractAn electronic stopping power model for boron, arsenic, and phosphorus ion implantation into single-crystal Si is reported over the energy range fr'om a few keV to several MeV, for both offand on-axis implant angles relative to the <100> crystallographic direction. Combined with previously developed models for damage accumulation, this model allows physically-based simulation of 3-D profiles over an extremely wide range of implant conditions. In particular, this allows modeling of MeV implants which are being used more and more frequently.

An Electronic Stopping Power Model in Single-Crystal Silicon from a Few KeV to Several MeV

AbstractAn electronic stopping power model for boron, arsenic, and phosphorus ion implantation into single-crystal Si is reported over the energy range from a few keV to several MeV, for both offand on-axis implant angles relative to the <100> crystallographic direction. Combined with previously developed models for damage accumulation, this model allows physically-based simulation of 3-D profiles over an extremely wide range of implant conditions. In particular, this allows modeling of MeV implants which are being used more and more frequently.

Monte Carlo simulation of arsenic ion implantation in (100) single-crystal silicon

In this paper is reported a new physically based Monte Carlo model and simulator for accurate simulation of arsenic ion implantation in (100) single-crystal silicon. A new damage generation model and an improved electronic stopping power model have been developed. These new physically based models greatly improve the capability for predicting arsenic as-implanted profiles. This new Monte Carlo model predicts very well the detailed profile dependence on the implant tilt and rotation angles as well as on the implant dose and energy over the energy range 15-180 keV.

Modeling of ion implantation in single-crystal silicon

In this paper are described ion implant models that have been developed at the University of Texas at Austin. In this activity the strategy consists of the development of computationally-efficient semi-empirical models and physically-based, more computationally intensive Monte Carlo models. The Dual-Pearson approach has been highly successful in the semi-empirical model development, because of its ability to account so well for the dependence of both the randomly scattered and the channeled parts of the implanted profile on all of the key implant parameters. The physically-based Monte Carlo models provide the theoretical foundation required for technology development and process control, and they serve as the basis for much of the computationally-efficient semi-empirical models. Depth profile models for B, BF 2, and As implants into single-crystal silicon, and a depth profile model for B implants through oxide layers into single-crystal Si have been developed. An accurate Monte Carlo simulator for boron implants into single-crystal Si or through oxide layers into single-crystal Si has also been developed. This simulator includes dependences on implant beam divergence, wafer temperature, and it has a new local-electron electronic stopping power model with explicit dependence on the local electron density in the Si lattice. In addition, we have developed a cumulative damage model for predicting the dose dependence and the resulting interstitial and vacancy distributions. We have also developed Monte Carlo simulators for BF 2 and As implants into single-crystal Si. The semi-empirical and physically-based models have been applied to develop a 2-dimensional model for boron implants through oxide layers into single-crystal Si. This computationally-efficient model has explicit dependence on energy, oxide thickness, dose, tilt angle, rotation angle, mask thickness, and mask edge orientation.

Electronic stopping of ions in the low velocity limit

The change in kinetic energy of an ion moving in an equilibrium electron gas is considered as a model for electronic stopping power. The exact small velocity limit is obtained for an ion of infinite mass. It is shown to be linear in the ion speed with a coefficient determined from the autocorrelation function for the force on the ion at rest in the equilibrium electron gas. The result has no limitations with respect to the ion charge, the electron coupling parameter, and the electron degeneracy parameter. Therefore it provides a firm basis for testing various theoretical approximations. Some comments are offered on the semiclassical limit, to provide a model appropriate for study via molecular dynamics simulation.

A New Local Electronic Stopping Model for the Monte Carlo Simulation of Arsenic Ion Implantation into (100) Single-Crystal Silicon

ABSTRACTIn this paper is reported the development and implementation of a new local electronic stopping model for arsenic ion implantation into single-crystal silicon. Monte Carlo binary collision (MCBC) models are appropriate for studying channeling effects since it is possible to include the crystal structure in the simulators. One major inadequacy of existing MCBC codes is that the electronic stopping of implanted ions is not accurately and physically accounted for, although it is absolutely necessary for predicting the channeling tails of the profiles. In order to address this need, we have developed a new electronic stopping power model using a directionally dependent electronic density (to account for valence bonding) and an electronic stopping power based on the density functional approach. This new model has been implemented in the MCBC code, UT-MARLOWE The predictions of UT-MARLOWE with this new model are in very good agreement with experimentally-measured secondary ion mass spectroscopy (SIMS) profiles for both on-axis and off-axis arsenic implants in the energy range of 15-180 keV.

Boron implantation in Si: Channeling effects studied by SIMS and simulation

The axial channeling behaviour of boron implants in , and silicon wafers is investigated by SIMS. Large differences of channeling characteristics such as channeled projected range (the projected range of channeled ions or channeling peak) and the fraction of channeled to implanted ions are observed among the three major crystal orientations. Within the critical angle, the channeling behaviour is very sensitive to the incidence beam angle with respect to crystal orientations. SIMS measurements are performed at different positions along several critical directions over a whole wafer. Well channeled profiles with an incidence beam angle to crystal orientations of 0 ° are obtained for each ion implantation energy and orientation. The results are used to test various models of ion implantation by simulation. A 3-parameter model for electronic stopping power of boron in silicon was proposed.