Collection efficiency and acceptance maps of electron detectors for understanding signal detection on modern scanning electron microscopy

Microscopy ◽  
2018 ◽  
Vol 67 (1) ◽  
pp. 18-29
Author(s):  
Toshihide Agemura ◽  
Takashi Sekiguchi
Keyword(s):  
Optical Axis ◽  
Collection Efficiency ◽  
Detection Mechanism ◽  
Electron Trajectories ◽  
Backscattered Electron ◽  
Electron Microscopes ◽  
Working Distance ◽  
Scanning Electron Microscopes ◽  
The Relationship ◽  
Scanning Electron

Abstract Collection efficiency and acceptance maps of typical detectors in modern scanning electron microscopes (SEMs) were investigated. Secondary and backscattered electron trajectories from a specimen to through-the-lens and under-the-lens detectors placed on an electron optical axis and an Everhart–Thornley detector mounted on a specimen chamber were simulated three-dimensionally. The acceptance maps were drawn as the relationship between the energy and angle of collected electrons under different working distances. The collection efficiency considering the detector sensitivity was also estimated for the various working distances. These data indicated that the acceptance maps and collection efficiency are keys to understand the detection mechanism and image contrast for each detector in the modern SEMs. Furthermore, the working distance is the dominant parameter because electron trajectories are drastically changed with the working distance.

Observation of GaAs/AlAs Superlattice Structures in both Secondary and Backscattcred Electron Imaging Modes with an Ultrahigh Resolution Scanning Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 404-405
Author(s):  
K. Ogura ◽  
A. Ono ◽  
S. Franchi ◽  
P.G. Merli ◽  
A. Migliori
Keyword(s):  
Gaas Layer ◽  
Objective Lens ◽  
Superlattice Structure ◽  
Backscattered Electron ◽  
Instrumental Resolution ◽  
Electron Microscopes ◽  
Superlattice Structures ◽  
Electron Imaging ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

In the last few years the development of Scanning Electron Microscopes (SEM), equipped with a Field Emission Gun (FEG) and using in-lens specimen position, has allowed a significant improvement of the instrumental resolution . This is a result of the fine and bright probe provided by the FEG and by the reduced aberration coefficients of the strongly excited objective lens. The smaller specimen size required by in-lens instruments (about 1 cm, in comparison to 15 or 20 cm of a conventional SEM) doesn’t represent a serious limitation in the evaluation of semiconductor process techniques, where the demand of high resolution is continuosly increasing. In this field one of the more interesting applications, already described (1), is the observation of superlattice structures.In this note we report a comparison between secondary electron (SE) and backscattered electron (BSE) images of a GaAs / AlAs superlattice structure, whose cross section is reported in fig. 1. The structure consist of a 3 nm GaAs layer and 10 pairs of 7 nm GaAs / 15 nm AlAs layers grown on GaAs substrate. Fig. 2, 3 and 4 are SE images of this structure made with a JEOL JSM 890 SEM operating at an accelerating voltage of 3, 15 and 25 kV respectively. Fig. 5 is a 25 kV BSE image of the same specimen. It can be noticed that the 3nm layer is always visible and that the 3 kV SE image, in spite of the poorer resolution, shows the same contrast of the BSE image. In the SE mode, an increase of the accelerating voltage produces a contrast inversion. On the contrary, when observed with BSE, the layers of GaAs are always brighter than the AlAs ones , independently of the beam energy.

Field of View and Image Distortion : A Review of Low Magnification Imaging In the Environmental and Conventional Scanning Electron Microscopes (SEM)

1997 ◽  
Vol 3 (S2) ◽  
pp. 1193-1194
Author(s):  
Brendan J. Griffin
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Field Of View ◽  
Depth Of Field ◽  
Aperture Size ◽  
Sem Image ◽  
Electron Microscopes ◽  
Working Distance ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

Most scanning electron microscopy is performed at low magnification; applications utilising the large depth of field nature of the SEM image rather than the high resolution aspect. Some environmental SEMs have a particular limitation in that the field of view is restricted by a pressure limiting aperture (PLA) at the beam entry point of the specimen chamber. With the original ElectroScan design, the E-3 model ESEM utilised a 500 urn aperture which gave a very limited field of view (∼550um diameter at a 10mm working distance [WD]). An increase of aperture size to ∼lmm provided an improved but still unsatisfactory field of view. The simplest option to increase the field of view in an ESEM was noted to be a movement of the pressure and field, limiting aperture back towards the scan coils1. This approach increased the field of view to ∼2mm, at a 10mm WD. A commercial low magnification device extended this concept and indicated the attainment of conventional fields of view.

scholarly journals Six-Axis SEM Stage

1993 ◽  
Vol 1 (2) ◽  
pp. 8-8
Author(s):  
Ross Murosako
Keyword(s):  
General Purpose ◽  
Image Features ◽  
Signal Collection ◽  
Specimen Orientation ◽  
Electron Microscopes ◽  
Working Distance ◽  
Scanning Electron Microscopes ◽  
Five Axis ◽  
Picture Frame ◽  
Scanning Electron

The primary function of an SEM specimen stage is to optimize the orientation of the specimen to the signal detectors. The ease and precision with which the stage executes this function determine its utility to the microscopist. While the majority of scanning electron microscopes are equipped with general purpose five-axis specimen stages, a six-axis stage can significantly enhance specimen orientation. Specimen manipulation can be further simplified by incorporation of a six-axis hand controller that enables the microscopist to move the specimen intuitively as if the specimen were held directly in the hand.SEM manufacturers typically install general purpose five-axis specimen stages in their scanning electron microscopes. In addition to translation along the X and Y axes, these stages are capable of tilt (T), elevation (Z motion), and rotation (R). Tilt directs the specimen surface toward the secondary electron detector to optimize signal collection. Elevation adjusts the working distance while rotation orients specific image features within the picture frame.

Effects of Nd: YAG Laser Welding Parameters on the Microstructure of 21% Cr Ferritic Stainless Steel

2011 ◽  
Vol 291-294 ◽  
pp. 999-1002
Author(s):  
Ke Ping Geng ◽  
Sheng Sun Hu ◽  
Jun Qi Shen ◽  
Jian Han ◽  
Hai Gang Xu
Keyword(s):  
Laser Welding ◽  
Optical Microscope ◽  
Welding Parameters ◽  
Slow Cooling ◽  
Yag Laser ◽  
Average Grain Size ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
The Relationship ◽  
Scanning Electron

21% Cr with Ti-Nb dual stabilized ferritic stainless was welded using Nd: YAG laser. The relationship between microstructure and parameters of laser welding was examined. The microstructure was investigated by using the optical microscope and scanning electron microscopes. The average grain size of the HAZ was increased with increasing heat input due to the slow cooling rate. Large precipitates as TiN, TiC and Nb(C,N) were dissolved in the HAZ. Fine precipitates which supposed to be TiC was formed uniformly distributed in the case of the fusion zones.

Hitachi Scanning Electron Microscope

1968 ◽  
Vol 26 ◽  
pp. 374-375
Author(s):  
T. Fujiyasu ◽  
K. Hara ◽  
H. Tamura
Keyword(s):  
Optical Axis ◽  
Electrical Potential ◽  
Objective Lens ◽  
List Type ◽  
Type Number ◽  
Lens System ◽  
Mechanical Vibrations ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

The demand for scanning electron microscopes is growing rapidly and exciting new fields of application have developed for this type of instrument. Hitachi, Ltd. has developed this type of instrument the details of which are described in this paper.A three stage demagnification lens system is used in the instrument. External magnetic and electrical disturbances and mechanical vibrations have been reduced.Aperture plates with different bore diameters are located above the condenser lens and deflection coil and the objective lens to reduce contamination by the fixed apertures in these lenses. An electromagnetic stigmator is provided in the objective lens field.The specimen stage permits X-, Y- and Z- axes movements as well as rotational tilting. The rotational tilting is such that its central axis is always coincident with the optical axis independent of the X-, Y- and Z- axes movements. Terminals are also provided which permit voltage measurements and to observe the electrical potential distribution of semi conductors.

Take-off Angle Imaging: A New Image Mode for Scanning Electron Microscopy

2013 ◽  
Vol 21 (3) ◽  
pp. 22-25
Author(s):  
Nicholas C. Barbi ◽  
Richard B. Mott
Keyword(s):  
Electrical Current ◽  
Avalanche Photodiode ◽  
Si Substrate ◽  
Silicon Photomultiplier ◽  
Silicon Photomultipliers ◽  
X Ray ◽  
Backscattered Electron ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

Traditional electron detectors for scanning electron microscopes (SEMs) are the Everhart-Thornley detector located on one side of the specimen and the overhead backscattered electron detector (BSED), usually mounted under the final lens. In 2011 PulseTor introduced an efficient BSED based on scintillator/silicon photomultipler technology that is small enough to be mounted on the tip of an X-ray detector. The scintillator converts the electron signal to light, which is in turn converted to an electrical current in the silicon photomultiplier (SiPM). Silicon photomultipliers were initially developed in Russia in the 1990s. The review article by Dolgoshein et al. cites much of the historical development. Following the recent work of Piemonte and others, the SiPM consists of an array of many identical and independent detecting elements (microcells) connected in parallel on a common Si substrate. Each microcell is an avalanche photodiode only tens of micrometers in size.

scholarly journals Depth Information Available from the Backscattered Electron Signal

1995 ◽  
Vol 3 (6) ◽  
pp. 8-9
Author(s):  
V.N.E. Robinson
Keyword(s):  
Surface Topography ◽  
Atomic Number ◽  
Secondary Electron ◽  
Low Voltage ◽  
Depth Information ◽  
New Techniques ◽  
Backscattered Electron ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

Although the secondary electron (SE) signal is still the most commonly used signal in scanning electron microscopes (SEMs), the backscattered electron (BSE) signal is now in wide use. Imaging both atomic number and surface topography have been the major applications of BSE detectors, with some applications in channelling, magnetic contrast and similar specialized applications. Over the last few years, low voltage BSE imaging has been used for imaging surface features to a depth of a few nm. But the BSE signal contains much more information and new techniques are being developed to take advantage of its versatility.

In environmental Scanning Electron Microscopy, the secondary electron signal reveals surface information not accessible by conventional backscattered electron signals

1989 ◽  
Vol 47 ◽  
pp. 78-79
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Vacuum ◽  
Environmental Scanning Electron Microscopy ◽  
Environmental Scanning ◽  
Specimen Preparation ◽  
Dynamic Events ◽  
Backscattered Electron ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

Environmental scanning electron microscopes (ESEM) operate at high as well as at low vacuum (<2.5 kPa: ~20 Torr) but utilize all advantages of conventional high vacuum SEM (large specimen size, high depth of focus and specimen tilt capability, TV-rate scanning for imaging dynamic events). They have the advantage of imaging wet specimens as well as insulators without the need of any specimen preparation. Previously, environmental scanning microscopy was restricted to the BSE signal collected with BSE detectors. SE signals cannot be collected with the Everhart-Thornley detector because it cannot operate at low vacuum. Using positively biased electron collectors, it is now possible to collect an SE signal. However, the origin and quality of this signal need to be further characterized.An ElectroScan ESEM was used equipped with SE and BSE detectors and operated at 7-30 kV with partial water pressures of 0.1-2.5 kPa (∼1-20 Torr).

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