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Browse Prior Art Database

Electron Extraction Grid to Prevent Surface Charging

IP.com Disclosure Number: IPCOM000042950D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Rubloff, GW: AUTHOR

Abstract

A number of important microanalysis techniques rely on measuring electrons which are emitted from a surface. For insulating samples, the charging of the surface can hinder the measurement of electrons, particularly in those cases where not only the electron current, but also its energy distribution, is to be measured. To solve this problem, the prior art has used an electron flood gun to direct slow electrons to the surface of the insulating sample, to reduce the net positive charge of the sample surface. However, the efficiency of this process is proportional to the surface charge, so the technique is considerably less sensitive for small surface charge. Another approach, changing the electric field at the sample surface by biasing the sample relative to the earth ground of the vacuum chamber, also has disadvantages.

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Electron Extraction Grid to Prevent Surface Charging

A number of important microanalysis techniques rely on measuring electrons which are emitted from a surface. For insulating samples, the charging of the surface can hinder the measurement of electrons, particularly in those cases where not only the electron current, but also its energy distribution, is to be measured. To solve this problem, the prior art has used an electron flood gun to direct slow electrons to the surface of the insulating sample, to reduce the net positive charge of the sample surface. However, the efficiency of this process is proportional to the surface charge, so the technique is considerably less sensitive for small surface charge. Another approach, changing the electric field at the sample surface by biasing the sample relative to the earth ground of the vacuum chamber, also has disadvantages. To solve these problems, an electron extraction grid is located between the sample and the analyzer. The secondary electron current emitted from the sample surface depends not only on the material properties of the sample, but also on the electric field at the surface. By changing the electric field at the sample surface, the net current (incident primary electron beam current minus emitted secondary electron current) can be changed considerably, often to the extent that the sign of the net current can be reversed. Thus, with proper adjustment of the surface electric field, the net current can be...