scholarly journals Using Your Beam Efficiently: Reducing Electron Dose in the STEM via Flyback Compensation

2022 ◽  
pp. 1-9
Author(s):  
Tiarnan Mullarkey ◽  
Jonathan J. P. Peters ◽  
Clive Downing ◽  
Lewys Jones
Keyword(s):  
Electron Beam ◽  
Strain Measurement ◽  
Scanning Transmission Electron Microscope ◽  
Absolute Minimum ◽  
Electron Dose ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Dose Efficiency ◽  
Specialized Hardware ◽  
Beam Damage

In the scanning transmission electron microscope, fast-scanning and frame-averaging are two widely used approaches for reducing electron-beam damage and increasing image signal noise ratio which require no additional specialized hardware. Unfortunately, for scans with short pixel dwell-times (less than 5 μs), line flyback time represents an increasingly wasteful overhead. Although beam exposure during flyback causes damage while yielding no useful information, scan coil hysteresis means that eliminating it entirely leads to unacceptably distorted images. In this work, we reduce this flyback to an absolute minimum by calibrating and correcting for this hysteresis in postprocessing. Substantial improvements in dose efficiency can be realized (up to 20%), while crystallographic and spatial fidelity is maintained for displacement/strain measurement.

Demonstration of Solid State Electron Optical Devices: Pixelated Fresnel Phase Lenses

1997 ◽  
Vol 3 (S2) ◽  
pp. 1037-1038
Author(s):  
Y. Ito ◽  
A.L. Bleloch ◽  
L.M. Brown
Keyword(s):  
Electron Beam ◽  
Solid State ◽  
Plane Wave ◽  
Focal Point ◽  
Scanning Transmission Electron Microscope ◽  
Nanometer Scale ◽  
Solid State Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Phase Manipulation

The ability to produce features of nanometer scale offers the possibility of phase manipulation of electron waves. The first conclusive results of phase manipulation by nanometer-scale diffraction gratings directly cut by the finely focused electron beam in a scanning transmission electron microscope (STEM) have already been demonstrated. This was achieved by using a grating with a “wedge” profile. This produced an asymmetrical diffraction pattern (in violation of Friedel's law). This violation is expected only if the grating acts mostly as a strong phase object. In this paper, a demonstration of solid state Pixelated Fresnel Phase (PFP) lenses for electrons will be presented. An array of these electron lenses can be easily formed and may be utilized, for example, as compact electron-beam forming lenses for parallel electron beam lithography.In general, an incident plane wave traveling along the optic axis of a lens experiences a phase shift. A conventional Fresnel phase lens, consisting of concentric zones with a modulo of 2π phase structure, focuses an incoming electron plane wave to its focal point.

Alignment of low-dose STEM images of unstained macromolecules

1984 ◽  
Vol 42 ◽  
pp. 162-163
Author(s):  
J. F. Hainfeld ◽  
P. S. Furcinitti ◽  
J. S. Wall
Keyword(s):  
Low Dose ◽  
Collection Efficiency ◽  
Scanning Transmission Electron Microscope ◽  
Single Particles ◽  
Low Contrast ◽  
Damage Rate ◽  
Software Packages ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Beam Damage

Several studies of molecular structure have successfully employed computer techniques to align images of single particles. Image processing software packages (e.g., P. R. Smith's MDPP system and J. Frank's SPIDER system) have also been developed to facilitate this work. Due to the low contrast and high beam damage rate involved in the use of unstained specimens, most single particle (i.e., non-crystalline) image alignment has been of negatively stained specimens. The scanning transmission electron microscope (STEM), which has a linear transfer function at high resolution rather than the oscillating one inherent to CEMs, operationally overcomes these limitations by providing low dose, high contrast images of unstained material with high collection efficiency.

Cutting of 20 Å holes and lines in metal-β-aluminas

1983 ◽  
Vol 41 ◽  
pp. 100-101 ◽  
Author(s):  
M.E. Mochel ◽  
C. J. Humphreys ◽  
J. M. Mochel ◽  
J. A. Eades
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Carbon Film ◽  
Scanning Transmission Electron Microscope ◽  
High Electron ◽  
Transmission Electron ◽  
Solid Substrates ◽  
Scanning Transmission ◽  
Very High

Holes 20 Å in diameter and fine lines 20 Å wide can be cut in the metal-β-aluminas using the 10 Å electron beam of the Vacuum Generators, HB5 scanning transmission electron microscope. The minimum current density required for cutting was 103 amp/cm2. Electron energies of 40,60,80,100 keV were used.This technique has higher resolution than current lithography methods and is direct, requiring no chemical development. The width of isolated lines made on solid substrates is currently about .1μm (Ahmed and McMahon, 1981) and .03μm (Jackel et al., 1980). M. Isaacson and A. Murry have carried out electron beam writing on NaCl crystals supported on a carbon film on the scale we report here.In our case uniform 20Å holes and lines can be cut through self-supporting 1000A thick slabs of sodium-β-alumina to provide very high electron contrast. Once cut, the β-aluminas are stable and will tolerate exposure to air without degradation of the electron cut patterns. They may be used directly as masks (eg. for ion implantation). We believe they could be cut on the substrate with no damage to the underlying material.

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