Marian Mankos - Academia.edu (original) (raw)

Papers by Marian Mankos

Creating, manipulating, and detecting coherent electrons is at the heart of future quantum micros... more Creating, manipulating, and detecting coherent electrons is at the heart of future quantum microscopy and spectroscopy technologies. Leveraging and specifically altering the quantum features of an electron beam source at low temperatures can enhance its emission properties. Here, we describe electron field emission from a monocrystalline, superconducting niobium nanotip at a temperature of 5.9 K. The emitted electron energy spectrum reveals an ultra-narrow distribution down to 16 meV due to tunable resonant tunneling field emission via localized band states at a nano-protrusion's apex and a cutoff at the sharp low-temperature Fermi-edge. This is an order of magnitude lower than for conventional field emission electron sources. The self-focusing geometry of the tip leads to emission in an angle of 3.7 • , a reduced brightness of 3.8 × 10 8 A/(m 2 sr V), and a stability of hours at 4.1 nA beam current and 69 meV energy width. This source will decrease the impact of lens aberration and enable new modes in low-energy electron microscopy, electron energy loss spectroscopy, and high-resolution vibrational spectroscopy.

Ultramicroscopy, 2019

An electron optical column has been designed for High Resolution Electron Energy Loss Microscopy ... more An electron optical column has been designed for High Resolution Electron Energy Loss Microscopy (HREELM). The column is composed of electron lenses and a beam separator that are placed between an electron source based on a laser excited cesium atom beam and a time-of-flight (ToF) spectrometer or a hemispherical analyzer (HSA). The instrument will be able to perform full field low energy electron imaging of surfaces with sub-micron spatial resolution and meV energy resolution necessary for the analysis of local vibrational spectra. Thus, non-contact, real space mapping of microscopic variations in vibrational levels will be made possible. A second imaging mode will allow for the mapping of the phonon dispersion relations from microscopic regions defined by an appropriate field aperture.

Advances in Imaging and Electron Physics Including Proceedings CPO-10, 2019

Abstract Multi-pass transmission electron microscopy is a novel technique that promises to reduce... more Abstract Multi-pass transmission electron microscopy is a novel technique that promises to reduce the required electron dose to the specimen for a desired signal-to-noise ratio by increasing the change to the phase of the electron wave that is imparted by the specimen. In this technique, the electron beam interacts elastically with the specimen multiple times so that the change in the phase accumulates before reaching the detector. Past simulations have predicted an improvement in resolution and sensitivity for a range of applications, and an order-of-magnitude reduction in damage at equivalent resolution. Here, the electron-optical design of a 10 keV multi-pass transmission electron microscope that is currently under construction is examined.

Superconductor Science and Technology, 2022

Ultra-stable, tunable magnetic ﬁelds are desirable for a wide range of applications in medical im... more Ultra-stable, tunable magnetic ﬁelds are desirable for a wide range of applications in medical imaging, electron microscopy, quantum science, and atomic physics. Superconducting magnets operated in persistent current mode, with device current ﬂowing in a closed superconducting loop disconnected from a power source, are a common approach for applications with the most stringent requirements on temporal ﬁeld stability. We present a method for active control of this persistent current by means of dynamic inductance change within the superconducting circuit. For a ﬁrst realization of this general technique, we consider a variable superconducting inductor placed in series with the main magnet. The inductor acts as a dynamic ﬂux storage device capable of transferring ﬂux to or from the main magnet through inductance change. This allows for ﬁne and fast adjustments of the persistent current without the use of thermal switches that limit the speed and accuracy of many present-day methods. W...

Proceedings, annual meeting, Electron Microscopy Society of America, 1992

A novel detection system has been designed and realized experimentally on the HB5 STEM instrument... more A novel detection system has been designed and realized experimentally on the HB5 STEM instrument. Shadow images, diffraction patterns as well as high-angle annular dark field and bright field images are observed simultaneously with high efficiency using CCD and TV cameras. The microscope can be operated in a wide range of instrument modes which includes the implementation of new techniques for high resolution imaging.As shown in Fig. 1, the detection system has three triple choice stages. Diffracted beams can be collected by three P47 fast phosphor annular detectors inclined at 45 degree to the axis and having different inner and outer acceptance angles, which can be adjusted by the postspecimen lenses. The detector is observed through a window by a photomultiplier. The annular detectors have been used also for a new bright field STEM technique which utilizes the inner rim of the detectors to collect only the outermost annular part of the central beam and promises an improvement in...

Proceedings, annual meeting, Electron Microscopy Society of America, 1993

The new detection system of the HB5 STEM enables the operation of the microscope in a variety of ... more The new detection system of the HB5 STEM enables the operation of the microscope in a variety of modes. If the specimen is placed inside the objective lens, high resolution bright and dark field images revealing the microstructure can be obtained. Since the specimen is located in a high magnetic field, magnetic ordering phenomena are disturbed and no magnetic structure contrast is observed. In the out-of-field position, magnetic structure may be revealed in the Fresnel and Differential Phase Contrast modes of Lorentz Microscopy. Fresnel images are obtained with a static beam, i.e. the scanning coils are not excited. In the Fresnel mode the objective lens focus is changed slightly and domain walls appear in the shadow image as dark and bright lines, switching contrast when the objective lens is changed between overfocussing and underfocussing. Electrons, passing through the sample, are deflected by the Lorentz force and appear to converge towards or diverge from the domain walls.

Ultramicroscopy, 2019

Multi-pass transmission electron microscopy (MPTEM) has been proposed as a way to reduce damage t... more Multi-pass transmission electron microscopy (MPTEM) has been proposed as a way to reduce damage to radiation-sensitive materials. For the field of cryo-electron microscopy (cryo-EM), this would significantly reduce the number of projections needed to create a 3D model and would allow the imaging of lower-contrast, more heterogeneous samples. We have designed a 10 keV proof-of-concept MPTEM. The column features fast-switching gated electron mirrors which cause each electron to interrogate the sample multiple times. A linear approximation for the multi-pass contrast transfer function (CTF) is developed to explain how the resolution depends on the number of passes through the sample.

Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2016

A mirror electron monochromator has been developed for reducing the energy spread of commonly use... more A mirror electron monochromator has been developed for reducing the energy spread of commonly used high brightness electron sources from the characteristic range of 0.3-1 eV to values below 100 meV. The monochromator utilizes mirror optics and thereby exploits the symmetry inherent in reversing the electron trajectory to monochromatize the primary beam with a knife edge instead of a conventional slit. The performance of the key electron-optical components of the monochromator have been simulated. These components include the combination of an electron mirror with a magnetic prism array. In initial testing, the monochromator has demonstrated the ability to reduce the energy spread of a 5 keV electron beam that was generated by a Schottky electron emitter from its initial value of 0.65eV-0.75eV to 180 meV with an exit beam current exceeding 1 nA and to 100 meV with an exit beam current of 50 pA. Here, the attainable energy resolution was found to be limited by the noise on the

Ultramicroscopy, 2019

Advances in Imaging and Electron Physics Including Proceedings CPO-10, 2019

Superconductor Science and Technology, 2022

Proceedings, annual meeting, Electron Microscopy Society of America, 1992

Proceedings, annual meeting, Electron Microscopy Society of America, 1993

Ultramicroscopy, 2019

Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2016