Electron-beam physical vapor deposition
These atoms then precipitate into solid form, coating everything in the vacuum chamber (within line of sight) with a thin layer of the anode material.
[2] Multiple types of evaporation materials and electron guns can be used simultaneously in a single EBPVD system, each having a power from tens to hundreds of kilowatts.
The generated electron beam is accelerated to a high kinetic energy and directed towards the evaporation material.
Once temperature and vacuum level are sufficiently high, vapor will result from the melt or solid.
In this process these compounds, compacted in the form of an ingot, are evaporated in vacuum by the focused high-energy electron beam, and the vapors are directly condensed over the substrate.
Certain refractory oxides and carbides undergo fragmentation during their evaporation by the electron beam, resulting in a stoichiometry that is different from the initial material.
When the thermodynamic conditions are met, the vapors react with the gas in the vicinity of the substrate to form films.
As the vapors arrive at the surface, they chemically combine under proper thermodynamic conditions to form a metal carbide film.
Heating of the substrate allows increased adatom–substrate and adatom–film diffusion by giving the adatoms sufficient energy to overcome kinetic barriers.
If a rough film, such as metallic nanorods,[5] is desired substrate cooling with water or liquid nitrogen may be employed to reduce diffusion lifetime, positively bolstering surface kinetic barriers.
The material utilization efficiency is high relative to other methods, and the process offers structural and morphological control of films.
EBPVD is a line-of-sight deposition process when performed at a low enough pressure (roughly <10−4 Torr ).
Another potential problem is that filament degradation in the electron gun results in a non-uniform evaporation rate.
Strictly speaking, the slow transition from line-of-sight to scattered deposition is determined not only by pressure (or mean free path) but also by source-to-substrate distance.
