Electron Beam Degradation of Sulfide-Based Thin-Film Phosphors for Field Emission Flat Panel Displays

1998 ◽  
Vol 508 ◽  
Author(s):  
B.L. Abrams ◽  
T.A. Trottier ◽  
H.C. Swart ◽  
E. Lambers ◽  
P.H. Holloway
Keyword(s):  
Thin Film ◽  
Electron Beam ◽  
Surface Chemistry ◽  
Threshold Voltage ◽  
Degradation Process ◽  
Primary Electron ◽  
Flat Panel Displays ◽  
Primary Electron Beam ◽  
Atomic Species ◽  
Gas Pressures

AbstractThe change in cathodoluminescence (CL) brightness and changes in surface chemistry of the thin film phosphor, SrS:Ce, have been investigated using a scanning Auger electron spectrometer and an Oriel optical spectrometer. The data for SrS:Ce were compared to ZnS:Cu, Al, Au and Y2O2S:Eu powders all collected in a stainless steel UHV chamber with gas pressures of 10−6 Torr O2. In the presence of a 2kV primary electron beam, the amounts of C and S on the surface decreased while the oxygen concentration increased. As a result, ZnO, Y2O3 and presumably SrOx formed. This change in surface chemistry coincided with a decrease in CL brightness. SrS degraded much faster than ZnS or Y2O2S. The model for this degradation process suggests that the primary electron beam dissociated physisorbed molecules to reactive atomic species. These atomic species reacted with surface S and C, carrying them away and leaving behind an increasingly more impenetrable layer. Threshold voltage experiments were conducted to reveal where it becomes possible to measure the CL. This threshold voltage should be affected by the oxide layer discussed above. The implications for vacuums in an FED FPD will be discussed.

X-Ray Energy Dispersive Spectroscopy in the Environmental Scanning Electron Microscope

1998 ◽  
Vol 4 (S2) ◽  
pp. 182-183
Author(s):  
John F. Mansfield ◽  
Brett L. Pennington
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Energy Dispersive Spectroscopy ◽  
Primary Electron ◽  
Environmental Scanning ◽  
Primary Electron Beam ◽  
X Ray ◽  
Environmental Sem ◽  
Scanning Electron

The environmental scanning electron microscope (Environmental SEM) has proved to be a powerful tool in both materials science and the life sciences. Full characterization of materials in the environmental SEM often requires chemical analysis by X-ray energy dispersive spectroscopy (XEDS). However, the spatial resolution of the XEDS signal can be severely degraded by the gaseous environment in the sample chamber. At an operating pressure of 5Torr a significant fraction of the primary electron beam is scattered after it passes through the final pressure limiting aperture and before it strikes the sample. Bolon and Griffin have both published data that illustrates this effect very well. Bolon revealed that 45% of the primary electron beam was scattered by more than 25 μm in an Environmental SEM operating at an accelerating voltage of 30kV, with a water vapor pressure of 3Torr and a working distance of 15mm.

Review of Techniques for Overcoming XEDS Problems in the Environmental Scanning Electron Microscope

1997 ◽  
Vol 3 (S2) ◽  
pp. 1207-1208
Author(s):  
John Mansfield
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Primary Electron ◽  
Environmental Scanning Electron Microscope ◽  
Significant Fraction ◽  
Environmental Scanning ◽  
Primary Electron Beam ◽  
Environmental Sem ◽  
Scanning Electron

Full characterization of materials in the environmental scanning electron microscope (Environmental SEM) often requires chemical analysis by X-ray energy dispersive spectroscopy (XEDS). However, a major problem arises because the spatial resolution of the XEDS signal is severely degraded by the gaseous environment in the sample chamber. The significant fraction of the primary electron beam is scattered after it passes through the final pressure limiting aperture and before it strikes the sample. Bolon and Griffin have both published data that illustrates this effect very well. Bolon revealed that 45% of the primary electron beam was scattered by more than 25μm in an Environmental SEM operating at an accelerating voltage of 30kV, with a water vapor pressure of 3Torr and a working distance of 15mm. Griffin’s work demonstrated that even at higher voltages (30 kV), shorter working distances (<10mm) and lower chamber pressures (2Torr), there is a significant fraction of the electron beam scattered out to over 400 μm away from the point where the primary beam strikes the sample.

Quantitative Determination of Bi Segregation at Grain Boundaries in Cu Bicrystals

1997 ◽  
Vol 3 (S2) ◽  
pp. 535-536
Author(s):  
U. Alber ◽  
H. Müllejans ◽  
M. Rühle
Keyword(s):  
Electron Beam ◽  
Grain Boundaries ◽  
Primary Electron ◽  
Atomic Scale ◽  
Beam Diameter ◽  
Primary Electron Beam ◽  
Impurity Segregation ◽  
A Value ◽  
Bi Segregation ◽  
Beam Broadening

Impurity segregation at grain boundaries (GB) can be detected by EDS in a dedicated STEM. Quantification of the segregation requires not only quantification of the spectra but also consideration of the geometry of the experiment. Our aim was to obtain a value which characterises only the segregation of the impurity and is independent of experimental parameters. The problem is that the specimen composition at the GB is extremely inhomogeneous on an atomic scale in the case of Bi segregation at GBs in Cu. The analysed volume which is defined by the irradiated area and the beam broadening of the primary electron beam inside the specimen contains the interfacial plane as well as neighbouring bulk Cu. One approach is to put the focussed primary electron beam on the interface which is aligned edge on and acquire a spectrum. Both the primary beam diameter and the beam broadening inside the specimen have to be known.

scholarly journals DeepBeam: a machine learning framework for tuning the primary electron beam of the PRIMO Monte Carlo software

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Zbisław Tabor ◽  
Damian Kabat ◽  
Michael P. R. Waligórski
Keyword(s):  
Machine Learning ◽  
Monte Carlo ◽  
Electron Beam ◽  
Regression Models ◽  
Primary Electron ◽  
Support Vector ◽  
Linear Accelerators ◽  
Primary Electron Beam ◽  
Measured Dose ◽  
Beam Parameters

Abstract Background Any Monte Carlo simulation of dose delivery using medical accelerator-generated megavolt photon beams begins by simulating electrons of the primary electron beam interacting with a target. Because the electron beam characteristics of any single accelerator are unique and generally unknown, an appropriate model of an electron beam must be assumed before MC simulations can be run. The purpose of the present study is to develop a flexible framework with suitable regression models for estimating parameters of the model of primary electron beam in simulators of medical linear accelerators using real reference dose profiles measured in a water phantom. Methods All simulations were run using PRIMO MC simulator. Two regression models for estimating the parameters of the simulated primary electron beam, both based on machine learning, were developed. The first model applies Principal Component Analysis to measured dose profiles in order to extract principal features of the shapes of the these profiles. The PCA-obtained features are then used by Support Vector Regressors to estimate the parameters of the model of the electron beam. The second model, based on deep learning, consists of a set of encoders processing measured dose profiles, followed by a sequence of fully connected layers acting together, which solve the regression problem of estimating values of the electron beam parameters directly from the measured dose profiles. Results of the regression are then used to reconstruct the dose profiles based on the PCA model. Agreement between the measured and reconstructed profiles can be further improved by an optimization procedure resulting in the final estimates of the parameters of the model of the primary electron beam. These final estimates are then used to determine dose profiles in MC simulations. Results Analysed were a set of actually measured (real) dose profiles of 6 MV beams from a real Varian 2300 C/D accelerator, a set of simulated training profiles, and a separate set of simulated testing profiles, both generated for a range of parameters of the primary electron beam of the Varian 2300 C/D PRIMO simulator. Application of the two-stage procedure based on regression followed by reconstruction-based minimization of the difference between measured (real) and reconstructed profiles resulted in achieving consistent estimates of electron beam parameters and in a very good agreement between the measured and simulated photon beam profiles. Conclusions The proposed framework is a readily applicable and customizable tool which may be applied in tuning virtual primary electron beams of Monte Carlo simulators of linear accelerators. The codes, training and test data, together with readout procedures, are freely available at the site: https://github.com/taborzbislaw/DeepBeam.

Sign in / Sign up

Export Citation Format

Share Document