Physical Vapor Deposition

Physical Vapor Deposition is the proscess by which one substance is coated with another. This is needed to increase the conductivity of samples for observation within the scanning electron microscope, or to create shadows within surface replicas viewed in the transmission electron microscope.

The Common methodes of acomplishing this feat are the Evaporator and the Sputter coater.

Sputter Coater

This type of PVD is use most commonly in the sample preperation of SEM samples, due to having a higher scattering probability then dose the evaporator. This allows the sputter coater, dependent on the proscess gas, geometry and gas pressure, to coat areas not in direct line of sight to the target material.

The mechanism by which the sputter coater opperates is kinetik dislocation of target atoms from the target by impacting it with high speed Ions, typically of Argon.

Evaporator

The evaporator works based on the heating of the source material to such a temperature that it evaporates. This is typically accomblished either by Ohmic heating or by electron beam impact. Unlike the sputter coater, no proscess gas is used, instead the proscess is carried out under high or ultra high vacuum. This removes the likelyhood of atoms scattering, thus only coating surfaces in direct line of sight to the source.

This is useful for the creation of shadows in Surface replicas used in the transmission electron microscope, since the evaporation source acts in the same way as would a point light source, with the shadows being the spots most visible to the source at the time of coating.