Ion Beam Processing Of Materials Research Articles

Adaptive moving environment for efficient molecular dynamics simulations of high-fluence ion irradiation

Ion-beam processing of materials is widely supported by atomistic simulations by means of molecular dynamics. Although the approach has given several valuable insights, it has a limited operational window in both time and length scales. In particular, for high-fluence ion irradiation with multiple consecutive cascades, the direct molecular dynamics method becomes prohibitively time consuming.In this work, we propose a speed-up algorithm for molecular-dynamics simulations of multiple consecutive collision cascades employing an adaptive moving environment model. In the model, the computational power is primarily focused on calculating the atomic movement in the propagating cascade regions, while thermally equilibrated regions outside the cascades are excluded. Up to a five-fold efficiency increase was seen with the adaptive moving environment compared to classical molecular dynamics, without any significant statistical difference in the results of multiple individual ion-cascade simulations in a heterostructure of alternating Si and SiO2 layers. Simulations of temperature-driven dynamic annealing during high-fluence ion irradiation of Si nanopillars at elevated temperatures using the adaptive moving environment showed similar trends as experiments with respect to temperature dependence. The model is included in the atomistic simulator toolkit, COSIRMA (COmputer Simulator for IRradiation of MAterials), and can easily be enabled through the user-friendly graphical interface.

On the use of SRIM for computing radiation damage exposure

The SRIM (formerly TRIM) Monte Carlo simulation code is widely used to compute a number of parameters relevant to ion beam implantation and ion beam processing of materials. It also has the capability to compute a common radiation damage exposure unit known as atomic displacements per atom (dpa). Since dpa is a standard measure of primary radiation damage production, most researchers who employ ion beams as a tool for inducing radiation damage in materials use SRIM to determine the dpa associated with their irradiations. The use of SRIM for this purpose has been evaluated and comparisons have been made with an internationally-recognized standard definition of dpa, as well as more detailed atomistic simulations of atomic displacement cascades. Differences between the standard and SRIM-based dpa are discussed and recommendations for future usage of SRIM in radiation damage studies are made. In particular, it is recommended that when direct comparisons between ion and neutron data are intended, the Kinchin–Pease option of SRIM should be selected.

English

Ion beam processing of materials in general and semiconductors in particular, started with ion implantation in semiconductors; first used by Ohl at Bell Labs in 1952 toimprove the electrical characteristics of silicon point contact diodes by implanting H, He, N and Ar ions.The improvement was obvious but it was caused by surface damage and notthe ion implantation. However, in the process, ion implantation had an entry and slowly it became popular among the scientists and the technocrats. Thus, over the last six decades, demands continued for new and improved materials and devices that has pushed ion implanter to expand to ion beam technology. In the semiconductor industry alone, the processes have evolved so much so that in today’s world, there are morethan 4000 ion implanters in the IC fab lines apart from otherion beam-assisted processing machines. Ion beam deposition techniques, ion beam lithography, ion beam etching, ion beammilling are all ion beam beam-assisted techniques that arebeing extensively used in semiconductor industries. In this backdrop, it was thought that a compilation of uses of allthese techniques together with relevant tools of analysis toserve as a guide to the semiconductor scientists and technologists for a glimpse of the ongoing efforts being madein this direction. Fortunately enough, Indian research is not lagging in use of all these modern day technologies that will be evident as the reader will go from one article to the other of this special volume. Defence Science Journal, 2009, 59(4), pp.328-328 , DOI:http://dx.doi.org/10.14429/dsj.59.1530

MRS-I Emphasizes Polymeric Materials and Ion-Beam Processing of Materials at 2003 Conference

MRS-I Emphasizes Polymeric Materials and Ion-Beam Processing of Materials at 2003 Conference

The computer simulation of energetic particle-solid interactions

Over the last decade the use of computer simulation in predicting physical phenomena associated with ion beam processing of materials has increased both in use and reliability. This is partly due to the dramatic increase in computer power and decrease in computer cost, but is also being achieved due to an increased understanding of the physical processes occurring. With the increase in computer power has come not just the ability to perform more complex calculations but also the methods for complex data representation in animated form. By animating the results it is much easier to observe collective effects such as acoustic wave propagation at a surface due to, for example, molecule impact.

Surface Effects During Ion Beam Processing of Materials

AbstractMicrostructural changes of surfaces during ion implantation have been investigated on the atomic level by molecular dynamics computer simulations. Unlike past surface studies, which have been focused on the problem of sputtering, the current work examines the effects of collective materials response on surface topography. Collective behavior has been noted for the crystal interior in the context of thermal spikes, but we show here that it can lead to far more dramatic consequences at the surface. The investigation includes implantation in several metals, but emphasizing Pt, Si and Ge. In addition, the study includes the first simulations of implantations of a metallic glass, CuTi, and amorphous Si.

Ion Beam Deposition

Ion beam processing of materials has a tradition at Oak Ridge National Laboratory that is as old as the laboratory itself. Consequently, when we began looking for a competitive way to participate in the excitement and new physics beginning to emerge from the fabrication and study of artificially structured materials, it was natural to look for a growth technique that incorporated ion beam processing. Our division, the Solid State Division, has a variety of ion implantation and ion beam analysis accelerators which are integrated with pulsed-laser sources into ultrahigh vacuum (UHV) surface analysis and processing chambers. These facilities allow us to do ion beam and laser processing of materials in UHV at temperatures from liquid helium to several hundred degrees centigrade and to study these alterations in situ by a variety of ion beam (ion scattering, ion channeling, nuclear reactions, etc.) and surface analysis (low energy electron diffraction, Auger, etc.) techniques. Since isotope separation has been done continually at ORNL for almost 45 years, the idea and advantages for altering this technique to do materials fabrication in UHV were immediately obvious. In the following article we will briefly review the history of the ion beam deposition (IBD) concept, describe our preliminary apparatus, and point out the inherent advantages of IBD for fabricating and studying artificially structured materials. Recent results obtained by IBD will be presented.

Material Processing with Broad-Beam Ion Sources

During the past two decades, ionized gases have been increasingly applied to etching, modification, and deposition of materials in thin film form (1), often using radio frequency (rf) excited plasmas. In parallel, the technology of broad-beam, multi aperture ion sources has been extensively developed for space propulsion (2). Only in the past few years have these broad-beam ion sources been applied in a systematic fashion to materials problems. The purpose of this review is to describe the growth ofthis new area of ion beam processing of materials. To define the field more precisely, the ion beams referred to here are typically several cm to tens of cm in diameter, not mass­ separated, with ion energies of tens of eV to a few keY. Not included are finely focused ion beams for surface analytical studies; ion implantation and ion-mixing beams; ion beams for fusion injection; and single-aperture beams. The primary advantage of ion beam processing of materials lies in the control available with an ion beam as compared to other plasma processes. The ion flux and ion energy are easily measured and independently controlled, and the direction of ion impact on surfaces is controlled, since the beams operate in a low background gas pressure of typically 0.01 Pa. This review begins with a description of broad-beam multiaperture ion sources, emphasizing the design advances that have stimulated recent

イオンビーム加工とその応用

イオンビーム加工とその応用