In lens BSE detector with energy filtering.

We present a new type of an in-lens detector designed for Thermo Fisher Scientific (FEI) electron microscopes with the Elstar column. A key feature of it is high-pass energy filtering to enable the detection of low-loss backscattered electrons with their energy close to the primary beam energy. We show an application of the detector in imaging of a biological sample where the signal from these electrons leads to a significant improvement in resolution.

Novel simulation method of space charge effects in electron optical systems including emission of electrons.

We present a comprehensive numerical method for iterative computation of electron optical systems influenced by space charge which can accurately describe all effects in an optical system, including areas near a cathode tip and all crossovers. We use two different algorithms of evaluating the space charge distribution in different parts of the system. The Monte-Carlo based particle-in-cell method is used in the vicinity of the cathode. The algorithm based on the calculation of the current density distribution from an aberration polynomial is used for the rest of the system. We introduce a re-meshing algorithm which adapts the finite element mesh used for the field calculation in each iteration to the actual space charge distribution to keep it sufficiently fine in all areas with non-zero space charge. The algorithm is finally tested on a design of an experimental electron-welding machine developed at the ISI of the CAS.

Effect of sample tilt on PEEM resolution.

In electron microscopy design, the systems are usually assumed to be perfectly aligned or that possible small imperfections can be eliminated by simple multipole correctors (centering deflectors, stigmators) without loss of resolution. However, in some cases, like in the cathode lens between the sample and the objective lens in the photoemission electron microscope, even a small imperfection can impair the resolution significantly. Because of the strong field between the sample and the objective lens, even a small tilt of the sample generates a parasitic dipole field, which decreases resolution and causes image deformations. We present a simulation of the influence of a small sample tilt on the system resolution based on modern computational methods that enable simulation of the whole system including the parasitic fields, proper setting of centering deflectors and stigmators. The resolution is determined by simulating the point spread function and finding the size of its significant part. The procedure is shown on realistic data from the literature. We found out that the resolution becomes worse mainly in the direction of the parasitic dipole field.