Sidewall angle tuning in focused electron beam-induced processing.

Structures fabricated using focused electron beam-induced deposition (FEBID) have sloped sidewalls because of the very nature of the deposition process. For applications this is highly undesirable, especially when neighboring structures are interconnected. A new technique combining FEBID and focused electron beam-induced etching (FEBIE) has been developed to fabricate structures with vertical sidewalls.

A new approach for fast field calculation in electrostatic electron lens design and optimization.

In electron optics, calculation of the electric field plays a major role in all computations and simulations. Accurate field calculation methods such as the finite element method (FEM), boundary element method and finite difference method, have been used for years. However, such methods are computationally very expensive and make the computer simulation challenging or even infeasible when trying to apply automated design of electrostatic lens systems with many free parameters.

Imaging resonant micro-cantilever movement with ultrafast scanning electron microscopy.

Here, we demonstrate ultrafast scanning electron microscopy (SEM) for making ultrafast movies of mechanical oscillators at resonance with nanoscale spatiotemporal resolution. Locking the laser excitation pulse sequence to the electron probe pulses allows for video framerates over 50 MHz, well above the detector bandwidth, while maintaining the electron beam resolution and depth of focus. The pulsed laser excitation is tuned to the oscillator resonance with a pulse frequency modulation scheme.

Interaction-Free Measurement with Electrons.

Here, we experimentally demonstrate interaction-free measurements with electrons using a novel electron Mach-Zehnder interferometer. The flexible two-grating electron interferometer is constructed in a conventional transmission electron microscope and achieves high contrast in discrete output detectors, tunable alignment with independently movable beam splitters, and scanning capabilities for imaging. With this path-separated electron interferometer, which closely matches theoretical expectations, we demonstrate electron interaction-free measurements with an efficiency of 14±1%.

Electrostatic electron mirror in SEM for simultaneous imaging of top and bottom surfaces of a sample.

The use of electron mirrors in aberration correction and surface-sensitive microscopy techniques such as low-energy electron microscopy has been established. However, in this work, by implementing an easy to construct, fully electrostatic electron mirror system under a sample in a conventional scanning electron microscope (SEM), we present a new imaging scheme which allows us to form scanned images of the top and bottom surfaces of the sample simultaneously. We believe that this imaging scheme could be of great value to the field of in-situ SEM which has been limited to observation of dynamic changes such as crack propagation and other surface phenomena on one side of samples at a time.

Rebubbling and graft failure in Descemet membrane endothelial keratoplasty: a prospective Dutch registry study.

Aims: To identify risk factors for rebubbling, and early graft failure after Descemet membrane endothelial keratoplasty (DMEK).

Methods: In this prospective registry study, all consecutive DMEK procedures registered in the Netherlands Organ Transplant Registry were assessed (n=752). Univariable and multivariable analysis was performed using logistic regression.

Trajectory displacement in a multi beam scanning electron microscope.

The analytical theory of statistical Coulomb interactions allows to determine the trajectory displacement in a single rotationally symmetrical beam with well-behaved spatial and angular particle distributions. This can be used to estimate the trajectory displacement in a multi-beam system using the so called fully-filled segment approximation. This approach predicts full compensation of trajectory displacement for a specific setup of the system.

Quality of vision and vision-related quality of life after Descemet membrane endothelial keratoplasty: a randomized clinical trial.

Purpose: To compare quality of vision and vision-related quality of life (QOL) in patients undergoing Descemet membrane endothelial keratoplasty (DMEK) or ultrathin Descemet stripping automated endothelial keratoplasty (DSAEK).

Methods: Fifty-four eyes of 54 patients with Fuchs' dystrophy from six corneal clinics in the Netherlands were randomized to DMEK or ultrathin DSAEK and examined preoperatively, and 3, 6 and 12 months postoperatively. Main outcome measures were corneal higher-order aberrations (HOAs), contrast sensitivity, straylight and vision-related QOL.

Combined Focused Electron Beam-Induced Deposition and Etching for the Patterning of Dense Lines without Interconnecting Material.

High resolution dense lines patterned by focused electron beam-induced deposition (FEBID) have been demonstrated to be promising for lithography. One of the challenges is the presence of interconnecting material, which is often carbonaceous, between the lines as a result of the Gaussian line profile. We demonstrate the use of focused electron beam-induced etching (FEBIE) as a scanning electron microscope (SEM)-based direct-write technique for the removal of this interconnecting material, which can be implemented without removing the sample from the SEM for post processing.

Lock-in Ultrafast Electron Microscopy Simultaneously Visualizes Carrier Recombination and Interface-Mediated Trapping.

Visualizing charge carrier flow over interfaces or near surfaces meets great challenges concerning resolution and vastly different time scales of bulk and surface dynamics. Ultrafast or four-dimensional scanning electron microscopy (USEM) using a laser pump electron probe scheme circumvents the optical diffraction limit, but disentangling surface-mediated trapping and ultrafast carrier dynamics in a single measurement scheme has not yet been demonstrated. Here, we present lock-in USEM, which simultaneously visualizes fast bulk recombination and slow trapping.

Transmission imaging on a scintillator in a scanning electron microscope.

Large area electron microscopy (EM) imaging has long been difficult due to fundamental limits in throughput for conventional electron microscopes. New developments in transmission electron microscopy and multi-beam scanning electron microscopy (MBSEM) imaging have however made it possible to generate large EM datasets [1,2,3]. This article describes a transmission imaging technique that is suitable for a MBSEM as it allows for a relatively straightforward way of separating the signals generated by each beam.

Real-World Outcomes of DMEK: A Prospective Dutch registry study.

Purpose: This study analyzed real-world practice patterns, graft survival, and outcomes of Descemet membrane endothelial keratoplasty (DMEK) in the Netherlands.

Design: Population-based interventional clinical study.

Methods: In this prospective registry study, all consecutive primary DMEK procedures registered in the Netherlands Organ Transplant Registry were identified.

Descemet Membrane Endothelial Keratoplasty versus Ultrathin Descemet Stripping Automated Endothelial Keratoplasty: A Multicenter Randomized Controlled Clinical Trial.

Purpose: To compare best spectacle-corrected visual acuity (BSCVA), endothelial cell density (ECD), refractive astigmatism, and complications after Descemet membrane endothelial keratoplasty (DMEK) and ultrathin Descemet stripping automated endothelial keratoplasty (UT-DSAEK).

Design: Prospective, multicenter randomized controlled trial.

Participants: Fifty-four pseudophakic eyes of 54 patients with corneal endothelial dysfunction resulting from Fuchs endothelial corneal dystrophy were enrolled in 6 corneal centers in The Netherlands.

Beam displacement and blur caused by fast electron beam deflection.

Electrostatic beam blankers are an alternative to photo-emission sources for generating pulsed electron beams for Time-resolved Cathodoluminescence and Ultrafast Electron Microscopy. While the properties of beam blankers have been extensively investigated in the past for applications in lithography, characteristics such as the influence of blanking on imaging resolution have not been fully addressed. We derive general analytical expressions for the spot displacement and loss in resolution induced by deflecting the electron beam in a blanker.

Photoemission sources and beam blankers for ultrafast electron microscopy.

Observing atomic motions as they occur is the dream goal of ultrafast electron microscopy (UEM). Great progress has been made so far thanks to the efforts of many scientists in developing the photoemission sources and beam blankers needed to create short pulses of electrons for the UEM experiments. While details on these setups have typically been reported, a systematic overview of methods used to obtain a pulsed beam and a comparison of relevant source parameters have not yet been conducted.

Estimating Step Heights from Top-Down SEM Images.

Scanning electron microscopy (SEM) is one of the most common inspection methods in the semiconductor industry and in research labs. To extract the height of structures using SEM images, various techniques have been used, such as tilting a sample, or modifying the SEM tool with extra sources and/or detectors. However, none of these techniques focused on extraction of height information directly from top-down images.

Trial-based cost-effectiveness analysis of ultrathin Descemet stripping automated endothelial keratoplasty (UT-DSAEK) versus DSAEK.

Purpose: To evaluate the cost-effectiveness of ultrathin Descemet stripping automated endothelial keratoplasty (UT-DSAEK) versus standard DSAEK.

Methods: A cost-effectiveness analysis using data from a multicentre randomized clinical trial was performed. The time horizon was 12 months postoperatively.

Design and simulation of a linear electron cavity for quantum electron microscopy.

Quantum electron microscopy (QEM) is a measurement approach that could reduce sample radiation damage, which represents the main obstacle to sub-nanometer direct imaging of molecules in conventional electron microscopes. This method is based on the exploitation of interaction-free measurements in an electron resonator. In this work, we present the design of a linear resonant electron cavity, which is at the core of QEM.

Long-term Outcomes of Repeated Corneal Transplantations: A Prospective Dutch Registry Study.

Purpose: To compare long-term outcomes of repeated corneal transplantations (CT), based on primary indication (Fuchs endothelial dystrophy [FED] vs pseudophakic bullous keratoplasty [PBK]), surgical technique (penetrating keratoplasty [PK] vs endothelial keratoplasty [EK]), and indication for repeated grafting.

Methods: In this nonrandomized treatment comparison with national registry data (Netherlands Organ Transplantation Registry, NOTR), data on all consecutive repeated CT following primary PK or EK for FED and PBK between 1994 and 2015 were analyzed, with a maximal follow-up of 5 years. Regraft survival was analyzed using Kaplan-Meier survival curves and univariable and multivariable Cox regression analysis.

Design for an aberration corrected scanning electron microscope using miniature electron mirrors.

Resolution of scanning electron microscopes (SEMs) is determined by aberrations of the objective lens. It is well known that both spherical and chromatic aberrations can be compensated by placing a 90-degree bending magnet and an electron mirror in the beam path before the objective lens. Nevertheless, this approach has not led to wide use of these aberration correctors, partly because aberrations of the bending magnet can be a serious problem.

Automated sub-5 nm image registration in integrated correlative fluorescence and electron microscopy using cathodoluminescence pointers.

In the biological sciences, data from fluorescence and electron microscopy is correlated to allow fluorescence biomolecule identification within the cellular ultrastructure and/or ultrastructural analysis following live-cell imaging. High-accuracy (sub-100 nm) image overlay requires the addition of fiducial markers, which makes overlay accuracy dependent on the number of fiducials present in the region of interest. Here, we report an automated method for light-electron image overlay at high accuracy, i.

Time-resolved cathodoluminescence microscopy with sub-nanosecond beam blanking for direct evaluation of the local density of states.

We show cathodoluminescence-based time-resolved electron beam spectroscopy in order to directly probe the spontaneous emission decay rate that is modified by the local density of states in a nanoscale environment. In contrast to dedicated laser-triggered electron-microscopy setups, we use commercial hardware in a standard SEM, which allows us to easily switch from pulsed to continuous operation of the SEM. Electron pulses of 80-90 ps duration are generated by conjugate blanking of a high-brightness electron beam, which allows probing emitters within a large range of decay rates.

A Randomized Multicenter Clinical Trial of Ultrathin Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) versus DSAEK.

Objective: To compare visual acuity, refraction, endothelial cell density (ECD), and complications after Descemet stripping automated endothelial keratoplasty (DSAEK) and ultrathin DSAEK (UT-DSAEK).

Design: A multicenter, prospective, double-masked, randomized, controlled clinical trial.

Participants: From 66 patients with irreversible corneal endothelial dysfunction dues to Fuchs' dystrophy who enrolled from 4 tertiary medical centers in the Netherlands, 66 eyes were studied.

Changing Practice Patterns and Long-term Outcomes of Endothelial Versus Penetrating Keratoplasty: A Prospective Dutch Registry Study.

Purpose: To compare graft survival, best-corrected visual acuity (BCVA), endothelial cell density (ECD), and refraction following penetrating keratoplasty (PK) vs endothelial keratoplasty (EK) for Fuchs endothelial dystrophy (FED) and pseudophakic bullous keratopathy (PBK).

Design: Nonrandomized treatment comparison with national registry data.

Methods: All consecutive patients undergoing first keratoplasty for FED and PBK between 1998 and 2014 were analyzed, with a maximum follow-up of 5 years (mean ± SD follow-up 39 ± 20 months, range 0-60 months).