Extracting electron backscattering coefficients from backscattered electron micrographs

Electron backscattering micrographs possess the so-called Z-contrast, carrying information about the chemical compositions of phases present in microstructures. The intensity at a particular point in the backscattered electron micrograph is proportional to the signal detected at a corresponding point in the scan raster, which is, in turn, proportional to the electron backscattering coefficient of a phase at that point. This article introduces a simple method for extracting the electron backscattering coefficients of phases present in the microstructure, from the backscattered electron micrographs. This method is able to convert the micrograph's greyscale to the backscattering-coefficient-scale. The prerequisite involves the known backscattering coefficients for two phases in the micrograph. In this way, backscattering coefficients of other phases can be determined. The method is unable to determine the chemical compositions of phases or the presence of an element only from analysing the backscattered electron micrograph. Nevertheless, this method was found to be very powerful when combined with energy dispersive spectroscopy, and the calculations of backscattering coefficients.     

Correlated electron tunneling during the field electron emission

Elementary events of correlated electron tunneling from very small regions of a hollow metal emitter were detected. The most significant microscopic and macroscopic parameters favoring the appearance of multiparticle tunneling effects are considered.     

Scanning electron microscope calibration with simultaneous electron probe diameter determination

A method is proposed for calibrating a scanning electron microscope SEM by means of a slot-type linear measure, which enables one to determine simultaneously all the main parameters needed for linear measurements: video image magnification, electron-probe diameter, and the correction parameter for deriving the true sizes of relief elements from the distances between video signal peaks.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 62–64, June, 1994.     

Single electron spintronics

Single electron electronics is now well developed, and allows the manipulation of electrons one-by-one as they tunnel on and off a nanoscale conducting island. In the past decade or so, there have been concerted efforts in several laboratories to construct single electron devices incorporating ferromagnetic components in order to introduce spin functionality. The use of ferromagnetic electrodes with a non-magnetic island can lead to spin accumulation on the island. On the other hand, making the dot also ferromagnetic introduces new physics such as tunnelling magnetoresistance enhancement in the cotunnelling regime and manifestations of the Kondo effect. Such nanoscale islands are also found to have long spin lifetimes. Conventional spintronics makes use of the average spin-polarization of a large ensemble of electrons: this new approach offers the prospect of accessing the quantum properties of the electron, and is a candidate approach to the construction of solid-state spin-based qubits.     

Half the electron

J.J. Thomson discovered the electron a hundred years ago, but he never quite accepted that the electron does not obey the classical laws of electromagnetism that he used for discovering it. This article discusses the experiments made by Thomson to measure the charge of the electron and the charge per unit mass. The interpretation by Thomson of the experimental results is outlined including the electron's role in the atom and other speculations     

Unraveling electron mysteries

Over the last few years it has become increasingly important to keep track of single electron processes on the atomic scale. The reason for this trend is the ultimate goal of building and testing molecular devices. The combination of scanning tunneling microscopy with powerful modeling is now capable of treating some of the most important issues in this regime. Issues like spin polarization and magnetization, imaging of single electron states, chemical bonding, and energy transport on the single electron scale. We expect that the ultimate goal of understanding and measuring most processes on the level of single electrons can be reached within the near future.Events on the atomic level are governed by electron properties. This fact has profound implications on the direction materials research takes, once it focuses on single molecules and atoms.     

Few electron limit of n-type metal oxide semiconductor single electron transistors

We report the electronic transport on n-type silicon single electron transistors (SETs) fabricated in complementary metal oxide semiconductor (CMOS) technology. The n-type metal oxide silicon SETs (n-MOSSETs) are built within a pre-industrial fully depleted silicon on insulator (FDSOI) technology with a silicon thickness down to 10 nm on 200 mm wafers. The nominal channel size of 20 × 20 nm(2) is obtained by employing electron beam lithography for active and gate level patterning. The Coulomb blockade stability diagram is precisely resolved at 4.2 K and it exhibits large addition energies of tens of meV. The confinement of the electrons in the quantum dot has been modeled by using a current spin density functional theory (CS-DFT) method. CMOS technology enables massive production of SETs for ultimate nanoelectronic and quantum variable based devices.     

电子轰击离子源脉冲离化电子流的测量

本文讨论了脉冲测量技术在飞行时间质谱计电子轰击离子源中测量脉冲离化电子流的应用 ,分析了平均电流测量方法测量脉冲离化电子流的局限性 ,给出了实际的脉冲测量电路     

Design optimization of a hairpin electron source for electron beam welding

We report the optimization of the design and performance of recently reported hairpin tungsten electron source as a cathode in diode type geometry of the gun. The temperature maximum has been shifted close to the crown of the source. Focusing of the beam has been achieved up to 1 mm in diameter with Gaussian profile of the beam at the target. The perveance and power density measured are 10⁻⁵ A V^−3/2 and 10⁶ W cm⁻², respectively.     

Cold electron source with an electron multiplier illuminated by ultraviolet photons

A cold electron source has been developed using a microchannel plate (MCP) electron multiplier. Primary electron emission is initiated by illumination with ultraviolet photons from a diode. Final electron emission currents of up to 10 μA in continuous wave (CW) mode and 10 mA in pulsed mode have been achieved from a MCP with an active diameter of 5.5 mm. Electron emission generated by UV photons with a wavelength of 260 nm has been shown to be about 30 times more efficient than emission generated by photons with a wavelength of 300 nm. Application of this cold electron source in mass spectrometry is discussed.     

A scanning electron microscope study of the degradation of electron channelling effects in alkali halide crystals during electron irradiation

The effects ofin-situ, 25 kV electron irradiation on SEM electron channelling patterns from alkali halide crystals at room temperature are reported. Patterns were generated using wide beam and narrow beam methods. It is observed that after an initial period of irradiation, during which well defined high resolution patterns can be generated, degradation occurs. This is marked either by channelling line difiuseness or by waviness, depending on the method of generation. After prolonged irradiations, patterns can no longer be detected. Subsequent annealing experiments on irradiated NaCl show that patterns return to their original clarity if the annealing temperature is between 285 and 325‡C. Initial distortions (i.e. diffuseness and waviness) are attributed principally to the effects on the incident beam of irradiation induced surface electric fields; pattern loss, and subsequent recovery on annealing, is attributed to lattice distortion effects arising from beam-induced defect clusters.     

Measuring the diameter of an electron probe with a scanning electron microscope

An analysis is made of methods of measuring the size (diameter) of the electron probe of a scanning electron microscope. Methods involving the cutoff of a specified signal level and the use of an effective rectangular beam are examined.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 28–29, January, 1995.     

An electron spectrum and profile monitor for the UK free electron laser

A versatile electron spectrum monitor has been developed for the UK free electron laser project. The monitor uses secondary emission from 96 tungsten foils and microprocessor-controlled sampling electronics to produce a high-resolution electron energy spectrum. A 30-channel prototype is currently operating as a beam profile monitor and has been extensively used in emittance measurements at the Kelvin Laboratory linac.     

A superconducting electron spectrometer

The set-up and tests of an electron spectrometer for in-beam conversion electron measurements are described. A superconducting solenoid is used to transport the electrons from the target to cooled Si(Li) detectors. The solenoid is designed to produce either a homogeneous axially symmetric field of up to 2 T or a variety of field profiles by powering the inner and outer set of coils of the solenoid separately. The electron trajectories resulting for various field profiles are discussed. In-beam electron spectra taken in coincidence with electrons, gammas and alpha-particles are shown.     

Selected-area small-angle electron diffraction

Selected-area electron diffraction capable of resolving spacings up to 2000 Å from first-order discrete reflections has been achieved using a standard, double-condenser electron microscope. The technique allows photographing of the selected area, at sufficient magnification, that gives rise to the small-angle scattering pattern, in addition to the normal capabilities of obtaining related wide-angle diffraction and wide-angle and small-angle dark-field micrographs. Most, but not all, of the results of discrete and diffuse, small-angle electron diffraction studies from a large variety of specimens including drawn, annealed polyethylene, latex particles, evaporated gold particles, grating replicas, and slit edges have been explained on the basis of the structures observed in the corresponding electron micrographs. Small-angle electron diffraction is found to be more sensitive to defects in the packing of the scattering centres than small-angle X-ray scattering.     

Universal plasma electron source

The construction of universal plasma electron sources that allows to generate both focused electron beams and large cross-section beams within stationary and pulse mode of operation is proposed, without any essential change in the construction of the source. The special feature of the source is the stability of electron beam parameters over a wide range of pressure (up to 10⁻² mbar), which makes it possible to use it in difficult vacuum conditions caused by intensive gas emission from the treated surface. High stability of the focused electron beam parameters is achieved due to a special configuration of electric and magnetic fields in the region of electron extraction. Generating large cross-section beams, a weak dependence of beam parameters of gas pressure, is achieved by using the method of double-grid stabilization of the emitting plasma surface. Physical processes causing an increase in parameter stability are discussed.     

Probing Rydberg electron dynamics

Abstract

Recently, the excitation of various types of Rydberg wave packet has become a common method for studying quantum-classical correspondence, internal dynamics in the presence of strong electromagnetic fields, and possibilities for quantum control. This paper reviews several methods for probing the evolution of Rydberg electrons including the basic theory behind each method and what dynamical information can be obtained.     

High resolution electron tomography

Reaching atomic resolution in 3D has been the ultimate goal in the field of electron tomography for many years. Significant progress, both on the theoretical as well as the experimental side has recently resulted in several exciting examples demonstrating the ability to visualise atoms in 3D. In this paper, we will review the different steps that have pushed the resolution in 3D to the atomic level. A broad range of methodologies and practical examples together with their impact on materials science will be discussed. Finally, we will provide an outlook and will describe future challenges in the field of high resolution electron tomography.