Electron Beam Driven Disordering in Small Particles

1996 ◽  
Vol 439 ◽  
Author(s):  
Richard R. Vanfleet ◽  
Jack Mochel
Keyword(s):  
Electron Beam ◽  
Critical Size ◽  
Scanning Transmission Electron Microscope ◽  
Metal Particles ◽  
Small Particles ◽  
Transmission Electron ◽  
Platinum Clusters ◽  
Scanning Transmission ◽  
The Individual ◽  
Small Metal Particles

AbstractSmall metal particles in the range of a few nanometers in diameter are seen to progressively disorder when the 100 keV electron beam of a Scanning Transmission Electron Microscope (STEM) is held stationary on the particle. The diffraction pattern of the individual particle is seen to progress from an initial array of indexable diffraction spots to a mixture of diffraction spots and amorphous-like rings and finally to rings with no persistent diffraction spots. After the electron beam is removed, the particles will recrystallize after minutes or hours. Only particles below a critical size are seen to fully disorder. We have observed this in Platinum, Palladium, Rhodium, and Iridium and based on our model of disordering process believe it is a universal effect. It has also been observed with a Platinum Ruthenium alloy. We discuss the mechanism of this disordering and the structure of the resulting disordering particle for the case of Platinum clusters.

A microdiffraction study of Os10C(Co)24-2 in the Scanning Transmission Electron Microscope

1986 ◽  
Vol 44 ◽  
pp. 696-697 ◽  
Author(s):  
M. E. Mochel ◽  
R. I. Masel ◽  
J. M. Mochel
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Structural Information ◽  
Carbon Film ◽  
Scanning Transmission Electron Microscope ◽  
Metal Particles ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Small Metal Particles

Recent papers have discussed some of the difficulties in determining the structure of very small (<10Å) metal particles using electron microscopy. One of the ideas in the literature is that electron diffraction could provide structural information even under conditions where imaging is difficult. The purpose of the work reported here is to demonstrate that one can use electron diffraction techniques to obtain structural information about small metal particles, in this case 5Å osmium particles on a carbon film.

Studies of Ordering in Small Particles

1995 ◽  
Vol 398 ◽  
Author(s):  
U. Herr ◽  
M. Poilack ◽  
D.L. Olynick ◽  
J.M. Gibson ◽  
R.S. Averback
Keyword(s):  
Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
Partial Ordering ◽  
Ordered Structure ◽  
Small Particles ◽  
Experimental Conditions ◽  
Au Clusters ◽  
Transmission Electron ◽  
Scanning Transmission

ABSTRACTDisordered clusters of the intermetallic compounds Ni3Al and Cu3Au have been produced using a high pressure sputtering technique. The clusters are either embedded in a film or studied, in-situ in an UHV electron microscope. The evolution of the ordered structure upon annealing is studied. Using a scanning transmission electron microscope, electron diffraction is obtained from individual clusters. Partial ordering is observed in Cu3Au clusters which have been annealed below the bulk order-disorder transition temperature. Under the experimental conditions, only clusters with sizes of 10–15 nm or larger show ordering.

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.

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.

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.

Mass and Mass Loss Measurements on DNA and fd Phage

1972 ◽  
Vol 30 ◽  
pp. 186-187
Author(s):  
Joseph Wall
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Scanning Transmission Electron Microscope ◽  
Scattering Data ◽  
Mass Measurements ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Atomic Scattering ◽  
The Individual ◽  
Scattering Cross Sections

Mass measurements can be done with the scanning transmission electron microscope in a manner similar to the densitometry of conventional microscope plates. Since the measurements are made directly on the microscope output signal, however, there are none of the non-linearities associated with film. The two signals (proportional to normalized elastically and inelastically scattered currents) are recorded directly on digital tape for analysis.Mass can be determined from the scattering data using atomic scattering cross-sections and assuming the cross-section of an object is the sum of the individual atomic cross-sections. Since the elastic and inelastic cross-sections have different dependence on atomic number, it also is possible to estimate the average Z of the object being measured. These calculations are performed using a Nova 800 computer system which is interfaced directly to the microscope.

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