Monte Carlo simulation study of scanning Auger electron images

Abstract

Simulation of contrast formation in Auger electron imaging of surfaces is helpful for analyzing scanning Auger microscopy/microanalysis (SAM) images. In this work, we have extended our previous Monte Carlo model and the simulation method for calculation of scanning electron microscopy (SEM) images to SAM images of complex structures. The essentials of the simulation method are as follows. (1) We use a constructive solid geometry modeling for a sample geometry, which is complex in elemental distribution, as well as in topographical configuration and a ray-tracing technique in the calculation procedure of electron flight steps that across the different element zones. The combination of the basic objects filled with elements, alloys, or compounds enables the simulation to a variety of sample geometries. (2) Sampled Auger signal electrons with a characteristic energy are generated in the simulation following an inner-shell ionization event, whose description is based on the Castani’s inner-shell ionization cross section. This paper discusses in detail the features of simulated SAM images and of line scans for structured samples, i.e., the objects embedded in a matrix, under various experimental conditions (object size, location depth, beam energy, and the incident angle). Several effects are predicted and explained, such as the contrast reversion for nanoparticles in sizes of 10–60 nm, the contrast enhancement for particles made of different elements and wholly embedded in a matrix, and the artifact contrast due to nearby objects containing different elements. The simulated SAM images are also compared with the simulated SEM images of secondary electrons and of backscattered electrons. The results indicate that the Monte Carlo simulation can play an important role in quantitative SAM mapping.

IM3D: A parallel Monte Carlo code for efficient simulations of primary radiation displacements and damage in 3D geometry

“…The flexibility of the geometry description “language” and the corresponding optimization of the ion tracing procedure within the material structure are certainly the two most important aspects of a 3D model. In past years, we have successfully implemented the Constructive Solid Geometry (CSG) 60 61 and Finite Element Triangle Mesh (FETM) computational geometry libraries 62 63 to efficiently simulate particle transport in arbitrary 3D geometries 64 65 . In this paper, we introduce IM3D (Irradiated Microstructures in 3D), which uses the fast database indexing technique 56 on the scattering angle and standard physical parameters such as electronic stopping powers generated using “SRModule.exe” 54 , with the user’s choice of CSG/FETM library as the 3D structural description 64 65 .…”

“…The CSG method 60 61 uses simpler geometries to build a complex structure with Boolean operations: union, difference and intersection. By CSG modeling, a complex geometric structure can be constructed from a few basic, simple 3D body elements analytically described with few parameters.…”

“…The basic elements, such as the sphere, tetrahedron, cuboid, ellipsoid, taper, column, polyhedron, paraboloid, hyperboloid, and others, are implemented in the code to allow efficient calculation of intersecting points of an ion trajectory with object surface. Detailed construction processes can be found in refs 60 and 61 . There are two limitations.…”

“…In IM3D, the free-flight-paths of an ion between two successive collision events follow either a Poisson distribution with a mean free-flight-path (where n is the atomic density of the target) or a deterministic value specified by the user. Afterwards, a ray-tracing technique 60 61 for a complex geometric structure and space subdivision are introduced to accelerate the calculations 62 63 . Furthermore, three physical quantities, the free-flight-path, the direction deflection, and the kinetic energy, change after ion refraction at each surface/interface.…”

A Monte Carlo calculation of the secondary electron emission in the backward direction from a SiO2 macro-capillary

“…This paper is a preliminary work towards the study on the guiding transmission of the scanning electron beam through the borosilicate glass macro-capillary and uses a Monte Carlo method to reveal the quantitative features of the secondary electron emission from a SiO 2 macrocapillary. The Monte Carlo method has been widely and successfully applied as a theoretical tool to the studies on electron-solid interactions [11][12][13][14] and thus it is a suitable tool for the present study also. Specifically, the electron transport modeling mainly follows our previous work [15] which studied the electron transport in SiO 2 and the charging problems of structures with very complex geometries.…”