- The high voltage power supply provides 5 to 10KeV to accelerate the electrons from the filament to the evaporant
- Most of kinetic energy of electrons is converted to heat on impingement
Thermionic Gunsalso hot-cathode or hot-filament guns.
Most commonly used for evaporation.
Electrons are generated by hot filament of a high temperature alloy such as tungsten.
Schematic of self-accelarated hot-filament electron beam guns
(a)Linear-focus gun (i)electrostatically focused(ii)elctrostatically and magnetically focused
(b)Bent-beam electron gun with electromagnetic focusing and water-cooled evaporant support.
Plasma Guns
- Electrons are generated within a plasma. By proper application of electric potential, electrons can be extracted from the plasma to provide a useful energy beam similar to that obtained by hot-cathode guns.
- Cold-cathode guns
- Hot hollow cathode dischage(HCD) guns
Advantages
- High power density, and hence extremely high temperature (4000C), power utilized with more efficiency
- Wide range of control over evaporation rates, high deposition rates up to 75 E-6m/min
- E-beam concentrates on the evaporated surface, support structure for the evaporant is water-cooled, hence, interaction between evaporant and support materials are greatly reduced.
- There are no support structure problems so the boat, hearth, or other support structure can be fabricated of almost any material.
Disadvantages
- Interactions between ionized vapor with the hot filament lead to impurities in the deposited film.
Thermionic Gunsalso hot-cathode or hot-filament guns.
Most commonly used for evaporation.
Electrons are generated by hot filament of a high temperature alloy such as tungsten.
Schematic of self-accelarated hot-filament electron beam guns
(a)Linear-focus gun (i)electrostatically focused(ii)elctrostatically and magnetically focused
Most commonly used for evaporation.
Electrons are generated by hot filament of a high temperature alloy such as tungsten.