No abstract

The depth resolution for optical sectioning in the scanning transmission electron microscope is measured using the results of optical sectioning experiments of laterally extended objects. We show that the depth resolution depends on the numerical aperture of the objective lens as expected. We also find, however, that the depth resolution depends on the lateral extent of the object that is being imaged owing to a missing cone of information in the transfer function. We find that deconvolution methods generally have limited usefulness in this case, but that three-dimensional information can still be obtained with the aid of prior information for specific samples such as those consisting of supported nanoparticles. We go on to review how a confocal geometry may improve the depth resolution for extended objects. Finally, we present a review of recent work exploring the effect of dynamical diffraction in zone-axis-aligned crystals on the optical sectioning process.

The authors demonstrate that confocal imaging trajectories can be established in a transmission electron microscope fitted with two spherical aberration correctors. An atomic-scale electron beam, focused by aberration-corrected illumination optics, is directly imaged by a second aberration-corrected system. The initial experiment described indicates how aberration-corrected scanning confocal electron microscopy will allow three-dimensional imaging and analysis of materials with atomic lateral resolution and with a depth resolution of a few nanometers. The depth resolution in the confocal mode is shown to be robust to the uncorrected chromatic aberration of the lenses, unlike depth sectioning using a single lens.

Self-assembled silver nanoparticle (NP) arrays were produced by deposition at glancing angles on transparent stepped Al2O3 templates. The evolution of the plasmonic resonances has been monitored using reflection anisotropy spectroscopy (RAS) during growth. It is demonstrated that the morphology of the array can be tailored by changing the template structure, resulting in a large tunability of the optical resonances. In order to extract detailed information on the origin of the measured dichroic response of the system, a model based on dipolar interactions has been developed and the effect of tarnishing and morphological dispersion addressed.

SummaryDue to its low beam current and charge compensation mechanism He-Ion scanning microscopy is a very promising tool for imaging biological cells. However, to obtain relevant information, the method used for sample preparation is also critical. In this work, we have used a Carl Zeiss Orion Plus helium-ion microscope to study the effect of sample gold coating on the morphology of human colorectal adenocarcinoma Caco2 cells. The fixative glutaraldehyde was used and the selective gold coating of the samples was investigated. A comparative study with standard scanning electron microscopy is presented.