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Wednesday, January 29, 2020 | History

2 edition of Secondary ion emission. found in the catalog.

Secondary ion emission.

Hassan Bolouri

Secondary ion emission.

  • 352 Want to read
  • 10 Currently reading

Published by University of Salford in Salford .
Written in English


Edition Notes

PhD thesis, ElectricalEngineering.

SeriesD57337/85
ID Numbers
Open LibraryOL20904894M

In the modeling, the researchers considered some factors such as magnitude for SE attenuation length, s, and SE escape probability, A, of the materials of interest. For instance, SE emission can be enhanced by electrostatic fields and ultrahigh-frequency electrical fields as well as the porosity of materials. This side effect could be put to use by using some older valves e. With an electron multiplier an impact of a single ion starts off an electron cascade, resulting in a pulse of electrons which is recorded directly. This classical 1-D space charge limit SCL is derived for charged particles of zero initial energy, and is termed the Child-Langmuir Law.

It is therefore commonly used in static SIMS devices. Dependence of the coefficient of secondary electron emission of Pt and Mo on the energy of the incident electron beam. In this instance the positively charged screen grid can accelerate the electron stream sufficiently to cause secondary emission at the anode plate. This had the effect of increasing the plate-grid distance for a given tube size, increasing the transconductance of the tube and reducing its noise figure. Liquid metal ion sources are used for high-resolution work, since these can provide smaller beam diameters. This can give rise to excessive screen grid current.

They hit the electrode surface with sufficient energy to release a number of electrons through secondary emission. This type of ion gun is easy to operate and generates roughly focused but high current ion beams. It requires pulsed secondary ion generation using either a pulsed primary ion gun or a pulsed secondary ion extraction. However, numerical simulation has been recently developed by Choiniere et al. This theory accounts for and conserves particle energy and angular momentum.


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Secondary ion emission. book

The reduction in mass per unit volume, for this same comparison, is 2. A secondary ion Secondary ion emission. book spectrometer consists of 1 a primary ion gun generating the primary ion beam2 a primary ion column, accelerating and focusing the beam onto the sample and in some devices an opportunity to separate the primary ion species by Wien filter or to pulse the beam3 high vacuum sample chamber holding the sample and the secondary ion extraction lens, 4 a mass analyser separating the ions according to their mass-to-charge ratio, and 5 a detector.

Its range of beam diameter microns is limited, with the sensitivity of the technique suffering as the beam diameter is reduced, since less ions for analysis are sputtered from the material.

High energy usually several keV ions are supplied by an ion gun 1 or 2 and focused on to the target sample 3which ionizes and sputters some atoms off the surface 4. The voltage of the collecting structure with respect to the ambient plasma, as well as the ambient plasma density and temperature, determines the size of the sheath.

Other current collection mechanisms will then be discussed. Keywords Atom Diffusion Sorption adsorption catalyst crystal isotope mass spectrometry metals microscopy segregation semiconductor spectrometry spectroscopy structure Editors and affiliations.

The time of flight mass analyzer separates the ions in a field-free drift path according to their velocity. They are often modeled as solid endbodies, except they are a small percentage of the solid spheres surface area. Liquid metal ion sources are used for high-resolution work, since these can provide smaller beam diameters.

SIMS conferences are devoted to two main issues: improving the application of SIMS in different and especially new fields, and understanding the ion formation process. This results in a unique phenomenon whereby the orbiting body 'rams' through the surrounding ions in the plasma creating a beam like effect in the reference frame of the orbiting body.

These results confirm previous predictions concerning the chemical nature of these "super-efficient" events.

Molecular Secondary Ion Emission

Layers of up to 10, angstroms thick can be depth-profiled using SIMS. System level configurations will be presented for each device, as well as the relative costs, benefits, and validation. These secondary ions are then collected by ion lenses 5 and filtered according to atomic mass 6then projected onto an electron multiplier 7, topFaraday cup 7, bottomor CCD screen 8.

Much has to be learned about the interactions between the sheath structure, the geometry of the mesh, the size of the endbody, and its relation to current collection. Also shown is that they are sensitive to the surface nanoenvironment. Work has been accomplished on current collection using porous spheres, by Stone et al.

Space charge limits across plasma sheaths[ edit ] In any application where electrons are emitted across a vacuum gap, there is a maximum allowable current for a given bias due to the self repulsion of the electron beam. This technology also has the potential to resolve a number of issues concerning EDTs.PHYSICS OF SECONDARY ION EMISSION Parameters of secondary ion emission Effect of the primary ion energy and current on SIE Effect of the target temperature on the SIE coefficient Angular dependence of secondary ion emission Secondary ion energy distribution Effect of primary ions and target material on secondary ion yield Effect of sample.

Secondary Ion Emission from Aluminum and Uanodium Under Energetic Ion Aombordment Patricia Gail Blauner Yale University The theoretical models proposed to describe secondary ion emission from surfaces under energetic ion bombardment have, to date, placed little or no emphasis on the role played by the primary ion species and energy.

This volume is devoted to the physics, instrumentation and analytical methods of secondary ion mass spectroscopy (SIMS) in relation to solid surfaces. It describes modern models of secondary ion formation and the factors influencing sensitivity of measurements and the range of applications.

The effects of grid transparency, photoemission, and secondary emission on the currents measured by an ion-electron collector experiment flown on OGO I are examined in detail. The calculated grid transparencies agree with laboratory tests. About these proceedings.

Introduction. This volume contains full proceedings of the Fourth International Conference on Secondary Ion Mass Spectrometry (SIMS-IV), held in the Minoo-Kanko Hotel, Osaka, Japan, from November 13th to 19th, This research examines how projectile characteristics, i.e.

the energy and number of constituent atoms in the projectile, influence multiple secondary ion emission, or "superefficient" events. In addition we examine the relevance of this technique for nanostructure investigation.

Yields have been measured for multi-ion emission events as a function of projectile characteristics. The data show that some collision Cited by: 2.