Browse Prior Art Database

Removing Particles From Surfaces Using Vacuum Electron Emission

IP.com Disclosure Number: IPCOM000039860D
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Cooper, DW: AUTHOR [+4]

Abstract

Small particulate matter in the micron and sub-micron range can be removed from surfaces by charging the particles by vacuum electron emission and subsequent removal of the particles from said surfaces by relatively high electric fields under vacuum. The figure shows a basic configuration, involving a substrate surface 1 (insulating or metallic) that has particles 2 on it, a vacuum gap between the surface and an insulated metallic collector electrode 3 and an illumination source 4. In a reasonably high vacuum, the vacuum gap provides a high dielectric strength to allow creation of high electric fields without sparkover. The dielectric breakdown strength of air reaches a minimum at a pressure much less that atmospheric. A high-quality vacuum allows making electric fields stronger than 1 MV/cm before field emission occurs.

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 52% of the total text.

Page 1 of 2

Removing Particles From Surfaces Using Vacuum Electron Emission

Small particulate matter in the micron and sub-micron range can be removed from surfaces by charging the particles by vacuum electron emission and subsequent removal of the particles from said surfaces by relatively high electric fields under vacuum. The figure shows a basic configuration, involving a substrate surface 1 (insulating or metallic) that has particles 2 on it, a vacuum gap between the surface and an insulated metallic collector electrode 3 and an illumination source 4. In a reasonably high vacuum, the vacuum gap provides a high dielectric strength to allow creation of high electric fields without sparkover. The dielectric breakdown strength of air reaches a minimum at a pressure much less that atmospheric. A high-quality vacuum allows making electric fields stronger than 1 MV/cm before field emission occurs. This makes possible stronger fields to remove particles with diameters of a few micrometers, possibly smaller. The preferred illumination source is an ultraviolet (UV) laser with photon energy sufficient to cause photoelectron emission from the particles, thereby leaving them positively charged. In the figure the illumination could be transmitted through one of the electrodes (such as metal-coated quartz for UV light) or the space between the electrodes could be illuminated from an angle that does not require that the light pass through the electrodes. In either geometry, multiple reflections are set up to enhance the illumination of the particles. The laser illumination can be very intense, pulsed (time-resolved), and focussed to specific regions of the surface, if desired. A second typ...