AVS2004 Session VT-TuA: Special Session at the 51st International AVS Symposium: "Fleming Centenary Session: The Birth and Evolution of Electronics"

Tuesday, November 16, 2004 1:20 PM in Room 303D

Tuesday Afternoon

Start	Invited?	Item
1:20 PM	Invited	VT-TuA-1 John Ambrose Fleming and the Beginning of Electronics H.F. Dylla (Jefferson Laboratory) This year is the centenary of John Ambrose Fleming’s momentous patent on the thermionic diode that was the birth of electronics. The "Edison effect" was discovered in 1882, this was later shown to be the result of thermionic emission of electrons from a heated filament into a vacuum. Edison did not make any significant devices based on this discovery and the effect was ignored for more that 8 years. In 1890 Fleming explained the effect and showed that the thermionic diode could be used as a rectifier. Fourteen years later Fleming filed this momentous 1904 patent on the thermionic diode that was the first public announcement of the electron tube; this revolutionized the development of radio and led to the invention of the thermionic triode by Lee de Forest in 1906. The background to these events will be described.
2:00 PM	Invited	VT-TuA-3 Vacuum and the Electron Tube Industry P. Redhead (National Research Council, Canada) The electron tube industry started with the patenting of the thermionic diode by John Ambrose Fleming in 1904. In the beginning the vacuum technology used by the infant tube industry was copied from the existing technology of the incandescent lamp industry. The growing demands for electron tubes for military and naval communications in the first world war led to major improvements in pumps and processing methods. By the 1920s the tube industry was developing mass production methods of processing to satisfy the demands for receiving tubes by the burgeoning radio industry. Further expansion of the tube industry in the 30s and 40s led to improvements in automatic equipment for processing vacuum tubes leading to the massive production rates of electron tubes in the second world war. The demands of radar during the war resulted in the development of techniques for large-scale production of microwave tubes and CRTs, the latter technology being put to good use later in TV picture tube production. The requirements of the electron tube industry dominated the vacuum industry for about 30 years until the introduction of the transistor. The developments in vacuum technology in the electron tube industry will be reviewed.
2:40 PM	Invited	VT-TuA-5 The Science and Technology of Pumping Residual Gases in Vacuum Tubes B. Ferrario (Saes Getters SpA, Italy) Since the invention of the vacuum oscillation valve by Fleming impressive developments have been made in the field of vacuum tubes and related applications. Vacuum tubes are nowadays widespread devices in spite of the introduction of the transistors as substitutes for the vacuum valves; here they are referred to as a large family of products which has been growing along many decades and include, for example, power vacuum tubes, x-ray tubes, CRTs for black&white and color television, and the more recent so called "thin CRTs", i.e. Field Emission Displays (FED).Vacuum science and technology have been playing an essential role in these developments and have evolved symbiotically with them, often generating fundamental knowledge useful for many other vacuum related applications. The evolution of the vacuum tube family has required an increasing degree of vacuum and longer lifetimes along with more and more cost effective manufacturing processes; particular attention has therefore been drawn on the phenomena which are responsible for vacuum deterioration after seal-off , among which outgassing is usually the most relevant. This has made the study of outgassing phenomena , the residual gas analysis, the selection of the appropriate materials and the optimization of the manufacturing processes increasingly important. Concurrently, important developments have been made concerning getters which, after seal-off, act as in situ pumps to countermeasure the outgassing effects; indeed they are used, in various materials and configurations, to minimize the total residual pressure and particularly the partial pressures of the so called “active” gases (H₂O, CO₂, H₂, O₂, etc.) which are usually most detrimental and account for most of the total pressure in vacuum tubes.This paper reviews the issues related to residual gases in vacuum tubes and the early as well as especially the modern getter solutions developed to ensure the desired residual gas pumping in various vacuum tube types.
3:20 PM	Invited	VT-TuA-7 Vacuum Microelectronic Devices and Vacuum Requirements G.E. McGuire, O.A. Shenderova, T. Tyler (International Technology Center) With the emergence of microfabrication and thin film deposition techniques developed by the semiconductor industry, it became apparent that miniature vacuum microelectronic devices could be developed. Using approaches as diverse as controlled evaporation, chemical etching (both wet isotropic and anisotropic and dry plasma etching) and controlled oxidation, sharp tips were formed with a radius of less than 50 nm. When integrated with a gate electrode, field enhancement at the tip showed the promise of very high field emission electron currents especially when arrays of >1 million tips per cm² could be produced. Even though currents above a milliamp have been achieved, vacuum microelectronic devices have not been adapted into widespread use. The vacuum environment of the device leads to changes in emission performance and premature failure that has limited the acceptance of the devices. Numerous approaches have been explored to improve and maintain the vacuum environment of the devices and enhance the vacuum conductance. In addition, device structures have been proposed that are less sensitive to the vacuum level and less susceptible to failure. An overview of these issues will be provided from a historical perspective.