Simulation of channeling contrast in scanning ion microscope images

Kaoru Ohya

doi:10.1063/1.5018126

Abstract

The scanning ion microscope (SIM) provides a distinct channeling contrast in backscattered ion (BSI) and secondary electron (SE) images owing to its wide critical angle for ion channeling. In this report, we present a molecular dynamics (MD) simulation of a crystalline sample’s channeling contrast that has been scanned by ion beams of 30 keV He, Ne, and Ga in the SIM. A middle portion of the sample surface inclined at different angles against neighboring sides oriented toward the ions’ channeling direction. Line profiles of the BSI and SE yields along the surface reproduced crystalline-oriented changes that are expected for a transparency model. Nevertheless, a trajectory simulation of the ions in the sample according to the MD technique suggests some contrast differences from that of the model for the BSI and SE images and for different ion species.

Highlights

The focused ion beam (FIB) works as a probe for a scanning ion microscope (SIM) that constructs an image of a sample surface by scanning an ion beam across the surface and detects secondary electrons (SEs) and backscattered ions (BSIs), as with a scanning electron microscope (SEM)
A large critical angle of several to 10◦ is expected for ion channeling at tens-of-keV, which results in a distinct channeling contrast in the SIM compared with a backscattered electron (BSE) image in the SEM.[7,8]
An molecular dynamics (MD) simulation was planned for detailed understanding of the channeling contrast mechanism for crystalline samples scanned by ion beams of He, Ne, and Ga with the energy relevant to the SIM

Summary

Introduction

A focused ion beam (FIB) using a gallium (Ga) liquid metal ion source that produces several nm-sized beams has been commonly used as an important tool for fabricating micro- and nanostructures.[1,2] The FIB works as a probe for a scanning ion microscope (SIM) that constructs an image of a sample surface by scanning an ion beam across the surface and detects secondary electrons (SEs) and backscattered ions (BSIs), as with a scanning electron microscope (SEM). A large critical angle of several to 10◦ is expected for ion channeling at tens-of-keV, which results in a distinct channeling contrast in the SIM compared with a backscattered electron (BSE) image in the SEM.[7,8]. 2 Focused Ion Beam Systems: Basics and Applications, edited by N. Advances in Imaging and Electron Physics, edited by P. 6 Helium Ion microscopy, edited by G. The Stopping and Range of Ions in Solids (Pergamon, New York, 1985), Vol

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