title: Theoretical study of precision and accuracy of strain analysis by nano-beam electron diffraction.
abstract: Measurement of lattice strain is important to characterize semiconductor nanostructures. As strain has large influence on the electronic band structure, methods for the measurement of strain with high precision, accuracy and spatial resolution in a large field of view are mandatory. In this paper we present a theoretical study of precision and accuracy of measurement of strain by convergent nano-beam electron diffraction. It is found that the accuracy of the evaluation suffers from halos in the diffraction pattern caused by a variation of strain within the area covered by the focussed electron beam. This effect, which is expected to be strong at sharp interfaces between materials with different lattice plane distances, will be discussed for convergent-beam electron diffraction patterns using a conventional probe and for patterns formed by a precessing electron beam. Furthermore, we discuss approaches to optimize the accuracy of strain measured at interfaces. The study is based on the evaluation of diffraction patterns simulated for different realistic structures that have been investigated experimentally in former publications. These simulations account for thermal diffuse scattering using the frozen-lattice approach and the modulation-transfer function of the image-recording system. The influence of Poisson noise is also investigated.
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany. Electronic address: mahr@ifp.uni-bremen.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Mahr
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
authors.forename: Knut
authors.initials: K
authors.lastname: Müller-Caspary
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Grieb
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Schowalter
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Mehrtens
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
authors.forename: Florian F
authors.initials: FF
authors.lastname: Krause
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
authors.forename: Dennis
authors.initials: D
authors.lastname: Zillmann
authors.affiliation: Institut für Festkörperphysik, Universität Bremen, Otto-Hahn-Allee 1, D-28359 Bremen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Rosenauer
keywords: Accuracy; Electron diffraction; NBED; Precession; Precision; STEM; Strain measurement; TEM