tool is presented for the simulation of secondary electron (SE) emission in a scanning electron microscope (SEM). The tool is based on the Geant4 platform of CERN. The modularity of this platform makes it comparatively easy to add and test individual physical models. Our aim has been to develop a flexible and generally applicable tool, while at the same time including a good description of low-energy (<50 eV) interactions of electrons with matter. To this end we have combined Mott cross-sections with phonon-scattering based cross-sections for the elastic scattering of electrons, and we have adopted a dielectric function theory approach for inelastic scattering and generation of SEs. A detailed model of the electromagnetic fields from an actual SEM column has been included in the tool for ray tracing of secondary and backscattered electrons. Our models have been validated against experimental results through comparison of the simulation results with experimental yields, SE spectra and SEM images. It is demonstrated that the resulting simulation package is capable of quantitatively predicting experimental SEM images and is an important tool in building a deeper understanding of SEM imaging.

A combination of atomic resolution phase contrast electron microscopy and pulsed electron beams reveals pristine properties of MgCl 2 at 1.7 Å resolution that were previously masked by air and beam damage. Both the inter-and intra-layer bonding in pristine MgCl 2 are weak, which leads to uncommonly large local orientation variations that characterize this Ziegler-Natta catalyst support. By delivering electrons with 1-10 ps pulses and ≈160 ps delay times, phonons induced by the electron irradiation in the material are allowed to dissipate before the subsequent delivery of the next electron packet, thus mitigating phonon accumulations. As a result, the total electron dose can be extended by a factor of 80-100 to study genuine material properties at atomic resolution without causing object alterations, which is more effective than reducing the sample temperature. In conditions of minimal damage, beam currents approach femtoamperes with dose rates around 1 eÅ −2 s −1 . Generally, the utilization of pulsed electron beams is introduced herein to access genuine material properties while minimizing beam damage.

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Ultrashort, low-emittance electron pulses can be created at a high repetition rate by using a TM deflection cavity to sweep a continuous beam across an aperture. These pulses can be used for time-resolved electron microscopy with atomic spatial and temporal resolution at relatively large average currents. In order to demonstrate this, a cavity has been inserted in a transmission electron microscope, and picosecond pulses have been created. No significant increase of either emittance or energy spread has been measured for these pulses. At a peak current of 814 ± 2 pA, the root-mean-square transverse normalized emittance of the electron pulses is ɛ=(2.7±0.1)·10 m rad in the direction parallel to the streak of the cavity, and ɛ=(2.5±0.1)·10 m rad in the perpendicular direction for pulses with a pulse length of 1.1-1.3 ps. Under the same conditions, the emittance of the continuous beam is ɛ=ɛ=(2.5±0.1)·10 m rad. Furthermore, for both the pulsed and the continuous beam a full width at half maximum energy spread of 0.95 ± 0.05 eV has been measured.

Pinched discharge plasmas in tin vapor are candidates for application in future semiconductor lithography tools. This paper presents time-resolved measurements of Stark broadened linewidths in a pulsed tin discharge. Stark broadening parameters have been determined for four lines of the Sn III spectrum in the range from 522 to 538 nm, based on a cross-calibration to a Sn II line with a previously known Stark width. The influence of the electron temperature on the Stark widths is discussed. Results for the electron densities in the discharge are presented and compared to Thomson scattering results.