Vacuum systems are chambers where most of the gases present in the atmosphere have been removed by various pumping methods. Processes typically performed in vacuum chambers are evaporation and sputtering. Evaporation is a thermal process which is usually instituted at the lowest practical pressure. Sputtering requires that after low pressure is reached a gas be reintroduced into the chamber at a low pressure before the process can be initiated.
Vacuum evaporation is the process of heating up a material in vacuum until it gets to the point of vaporizing at a rate suitable for film deposition. This temperature can range from far below room temperature to over 3000° Celsius depending upon the material. There is a lower practical limitation in the range of 750° Celsius to prevent contamination from one deposition process to the next.
Sputtering
is the process of bombarding a material with heavy atoms or ions with sufficient
energy to dislodge the material thus allowing it to
transfer to a different location. The simplest form of sputtering is 
a
DC target where the target of material is insulated from the vacuum chamber
and connected to a source of high DC voltage. The high voltage creates a charge
at the target surface and at the same time strips an
electron from the sputtering gas (usually argon). Since the target has the
opposite charge to the argon ion, the ions are attracted to the target and
sputtering takes place as the argon ions impact the surface. It can be thought
of as atomic level billiard balls. Modern systems are usually magnetron systems
where a magnetic field close to the target creates additional ionization and
hence higher sputtering rates.
Differences
and Similarities
The appearance of sputtered or evaporated films is essentially identical. The energy imparted thermally (evaporation) is less than the energy imparted by sputtering, so sputtered films tend to be denser and better adhered than evaporated films. The distribution of sputtered material tends to be very broad due to the size of the target and also the fact that there are many atomic collisions taking place at sputtering pressure. All of the collisions change the direction of travel of material released from the target so sputtering tends to cover side walls of three dimensional objects. Evaporation is much more of a line-of-sight process which is preferable when it is not desirable to coat the side walls of structures.