Browse Prior Art Database

Contactless Measurement of Voltage Levels Using Photoemission

IP.com Disclosure Number: IPCOM000049985D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 34K

Publishing Venue

IBM

Related People

Rubloff, GW: AUTHOR

Abstract

This article describes the use of a photoemission technique to obtain high resolution, contactless measurement of voltage levels.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Contactless Measurement of Voltage Levels Using Photoemission

This article describes the use of a photoemission technique to obtain high resolution, contactless measurement of voltage levels.

It is known that an electron beam can be used to generate secondary (and Auger) electron distributions in which the kinetic energy of spectral features gives the voltage level of the specimen * . [Higher resolution determination of such voltages is possible using photoemission measurements of the position of the Fermi level cutoff of a metal surface.

In photoemission an ultraviolet or X-ray photon excites electrons to higher energy states by the fixed energy of the photon, producing emission of primary photoelectrons and also secondary electrons from the surface; their kinetic energy distribution (as measured with an electron energy analyzer) is depicted in the figure.

If the specimen voltage level is changed by delta V (<0 in the figure), the entire spectrum is rigidly shifted in energy by this amount. For a metal surface, a sharp Fermi level cutoff appears in this distribution at the high energy side, corresponding to the cutoff of the Fermi-Dirac distribution of occupation numbers of electron states. The intrinsic width of this cutoff is of the order kT, i.e., approximately 25 meV at room temperature. With the minimum resolution of common commercial analyzers of less than 50-100 meV, the cutoff is easily measurable at quite high resolution.

Using photoemission observations of the Fermi level cutoff to measure specimen voltages has several advantages. First, since the kinetic energy of electrons being measured is considerably higher than that for the secondary electron cutoff at the vacuum level (kinetic energies at the Fermi level are approximately 15-35 eV for ultrav...