Differential phase-contrast dark-field electron holography for strain mapping
Résumé
Strain mapping is an active area of research in transmission electron microscopy. Here we introduce a dark-field electron holographic technique that shares several aspects in common with both off-axis and in-line holography. Two incident and convergent plane waves are produced in front of the specimen thanks to an electrostatic biprism in the condenser system of a transmission electron microscope. The interference of electron beams diffracted by the illuminated crystal is then recorded in a defocused plane. The differential phase recovered from the hologram is directly proportional to the strain in the sample. The strain can be quantified if the separation of the images due to the defocus is precisely determined. The present technique has the advantage that the derivative of the phase is measured directly which allows us to avoid numerical differentiation. The distribution of the noise in the reconstructed strain maps is isotropic and more homogeneous. This technique was used to investigate different samples: a Si/SiGe superlattice, transistors with SiGe source/drain and epitaxial PZT thin films. © 2015 Elsevier B.V.
Mots clés
Differentiation (calculus)
Electron holography
Electrons
High resolution transmission electron microscopy
Mapping
Strain
Condenser systems
Dark field
Dark-field electron holographies
Differential phase
Differential phase contrast
Holographic technique
In-line holography
Numerical differentiation
Holograms
Article
controlled study
dark field electron holography
electron beam
holography
intermethod comparison
investigative procedures
microscope image
quantitative analysis
strain mapping
transmission electron microscopy