Subnanometer-accuracy optical distance ruler based on fluorescence quenching by transparent conductors

Available data: Complex refractive index of Indium Tin Oxide, http://dx.doi.org/10.4121/uuid:59febf27-a532-4ac9-8ec0-29d4195b2c8c Transparent conductive oxides (TCOs), such as the well-known indium-tin oxide, find widespread use in modern (nano)technological applications because of their unique combination of negligible optical absorption and good electric conductivity. We, however, show that despite the near-zero imaginary part of the refractive index that is responsible for the material’s transparency, TCOs drastically quench optical emitters when the emitter is within 10 nm from the TCO. Our results reveal that the pure near-field nature of this dissipation makes for an exquisite short-range optical ruler. Previous quenching-based optical rulers, based on interactions with plasmonic or graphene materials, have allowed measuring distances in the 20–100 nm range. Distances below 20 nm have, however, been hard to assess due to poor photon yields or weak absolute variations. We show that TCO-based rulers close this gap, allowing distance measurements with far-field optics in the 1–10 nm distance range with deep subnanometer sensitivity.ImPhys/Imaging PhysicsApplied Science

Inspection apparatus and replaceable door for a vacuum chamber of such an inspection apparatus and a method for operating an inspection apparatus

An inspection apparatus is provided comprising in combination at least an optical microscope and an ion- or electron microscope equipped with a source for emitting a primary beam of radiation to a sample in a sample holder. The apparatus may comprise a detector for detection of secondary radiation backscattered from the sample and induced by the primary beam. The optical microscope is equipped with an light collecting device to receive in use luminescence light emitted by the sample and to focus it on a photon-detector.IST/Imaging Science and TechnologyApplied Science

Correlating 3D light to 3D electron microscopy for systems biology

Whilst a ‘resolution revolution’ has taken place at the macromolecular scale in both electron microscopy and light microscopy, a ‘volume revolution’ has taken place at the tissue and organism level in both imaging modalities. At both ends of the scale – resolution and volume – there are concerted efforts to link the information from light and electron microscopes through correlative workflows to link structure to function. Here, we consider the status and potential of correlative imaging in the volume domain (3D CLEM).ImPhys/Charged Particle Optic

Integrated optical and charged particle inspection apparatus: Corrected version

The invention relates to an apparatus for inspecting a sample, equipped with a charged particle column for producing a focused beam of charged particles to observe or modify the sample, and an optical microscope to observe a region of interest on the sample as is observed by the charged particle beam or vice versa, the apparatus accommodated with a processing unit adapted and equipped for representing an image as generated with said column and an image as generated with said microscope, the unit further adapted for performing an alignment procedure mutually correlating a region of interest in one of said images wherein the alignment procedure involves detecting a change in the optical image as caused therein by the charged particle beam.ImPhys/Imaging PhysicsApplied Science

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. We use an atomic force microscope cantilever as a model resonator, for which we show ultrafast real-space imaging of the first and even the 2 MHz second harmonic oscillation as well as verification of power and frequency response via the ultrafast movies series. We detect oscillation amplitudes as small as 20 nm and as large as 9 μm. Our implementation of ultrafast SEM for visualizing nanoscale oscillatory dynamics adds temporal resolution to the domain of SEM, providing new avenues for the characterization and development of devices based on micro- and nanoscale resonant motion. ImPhys/Microscopy Instrumentation & Technique

Gap nanoantennas toward molecular plasmonic devices

Recently we have demonstrated that single fluorescent molecules can be used as non-perturbative vectorial probes of the local field. Here, we expand on such experiments exploiting fluorescence lifetime of single molecules to probe various types of gap nanoantennas. First, studies of the nanoantennas are carried out to evaluate the electric field. We then investigate hybrid systems composed by nanoantennas and randomly positioned fluorescent molecules. Finally, we present a fabrication scheme for the controlled placement of fluorescent molecules at welldefined positions with respect to the dimer nanoantenna, which is a more direct route to probe the local field in an a priori determined wayImaging Science and TechnologyApplied Science

ColorEM: analytical electron microscopy for element-guided identification and imaging of the building blocks of life

Nanometer-scale identification of multiple targets is crucial to understand how biomolecules regulate life. Markers, or probes, of specific biomolecules help to visualize and to identify. Electron microscopy (EM), the highest resolution imaging modality, provides ultrastructural information where several subcellular structures can be readily identified. For precise tagging of (macro)molecules, electron-dense probes, distinguishable in gray-scale EM, are being used. However, practically these genetically-encoded or immune-targeted probes are limited to three targets. In correlated microscopy, fluorescent signals are overlaid on the EM image, but typically without the nanometer-scale resolution and limited to visualization of few targets. Recently, analytical methods have become more sensitive, which has led to a renewed interest to explore these for imaging of elements and molecules in cells and tissues in EM. Here, we present the current state of nanoscale imaging of cells and tissues using energy dispersive X-ray analysis (EDX), electron energy loss spectroscopy (EELS), cathodoluminescence (CL), and touch upon secondary ion mass spectroscopy at the nanoscale (NanoSIMS). ColorEM is the term encompassing these analytical techniques the results of which are then displayed as false-color at the EM scale. We highlight how ColorEM will become a strong analytical nano-imaging tool in life science microscopy.ImPhys/Charged Particle Optic

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. In particular, we analyze the sensitivity of both measures to how precise the conjugate focus is aligned in between the deflector plates. We then work out the specific case of a beam blanker driven by a linear voltage ramp as was used in recent studies by others and by us. The result shows that the spot displacement and focus blur can be reduced to the same order as the electron beam probe size, even when using a beam blanker of millimeter or larger scale dimensions. An interesting result is that, by the right choice of the focus position in the deflector, either the spot displacement from the stationary position can be minimized, or the blur can be made zero but not both at the same time. Our results can be used both to characterize existing beam blanker setups and to design novel blankers. This can further develop the field of time-resolved electron microscopy by making it easier to generate pulses with a typical duration of tens of picoseconds in a regular scanning electron microscope at high spatial resolution.ImPhys/Charged Particle Optic

Concept and design of a beam blanker with integrated photoconductive switch for ultrafast electron microscopy

We present a new method to create ultrashort electron pulses by integrating a photoconductive switch with an electrostatic deflector. This paper discusses the feasibility of such a system by analytical and numerical calculations. We argue that ultrafast electron pulses can be achieved for micrometer scale dimensions of the blanker, which are feasible with MEMS-based fabrication technology. According to basic models, the design presented in this paper is capable of generating 100 fs electron pulses with spatial resolutions of less than 10 nm. Our concept for an ultrafast beam blanker (UFB) may provide an attractive alternative to perform ultrafast electron microscopy, as it does not require modification of the microscope nor realignment between DC and pulsed mode of operation. Moreover, only low laser pulse energies are required. Due to its small dimensions the UFB can be inserted in the beam line of a commercial microscope via standard entry ports for blankers or variable apertures. The use of a photoconductive switch ensures minimal jitter between laser and electron pulses.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ImPhys/Charged Particle OpticsImPhys/Quantitative Imagin

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. In this report, we outline the basic requirements and parameters that are important for UEM. Different types of imaging modes in UEM are analyzed and summarized. After reviewing and analyzing the different kinds of photoemission sources and beam blankers that have been reported in the literature, we estimate the reduced brightness for all the photoemission sources reviewed and compare this to the brightness in the continuous and blanked beams. As for the problem of pulse broadening caused by the repulsive forces between electrons, four main methods available to mitigate the dispersion are summarized. We anticipate that the analysis and conclusions provided in this manuscript will be instructive for designing an UEM setup and could thus push the further development of UEM.ImPhys/Charged Particle Optic