| 摘要 |
Disclosed is an electron-beam cathode which emits electrons in a cone-shaped pattern whose electron density is substantially uniform throughout the cone. The cathode is comprised of a needle-shaped piece of single crystal tungsten having dopant atoms of zirconium and oxygen in the bulk thereof, and having only a single (100) surface on the needle's tip. This cathode is formed by the steps providing a needle-shaped piece of single crystal tungsten having dopant atoms of zirconium and oxygen in the bulk thereof, and having a plurality of ring-shaped (100) surfaces on the needle's tip; and subsequently transforming those surfaces into diagonally oriented planar surfaces by heating the needle in an atmosphere of oxygen to diffuse tungsten atoms from the needle's tip to its sides.
|
