EQUIPOS DE PREPARACIÓN DE MUESTRAS: Carbon
and Metal Evaporators 
FEDELCO,
S.L.
CARBON AND METAL
EVAPORATORS PARA TEM/SEM:
Carbon
Films, because of their mechanical stability, good electrical
conductivity, and low background signal are commonly used in sample
preparation techniques for Electron Microscopy (EM). Thin films of the
order of up to 5 nm (50A) are used in Transmission Electron Microscopy
(TEM) as particle support and as isolating layers in autoradiography.
Thick films somewhat more than 5 nm (50A) are used in Scanning Electron
Microscopy (SEM) also for support, in addition to coating for X-Ray
Microanalysis. It may also be a requirement to subsequently treat
support films by means of Glow Discharge. In general there is a need for
all these films to be fine grain, even coating, with uniform and
reproducible film thickness.
The advent of Carbon fibre has resulted in a new principle for
Evaporation of Carbon in EM applications. The basis is a carbon filament
which at high temperature burns very quickly,somewhat in the order of 1
second or less, from which has evolved the terminology Carbon‘Flash’
Evaporation. This, together with the low total power input, due to short
coating times,distinguishing it from the somewhat longer process of
carbon rod evaporation. It is further distinguished in total cycle time,
which is approx. 4 minutes including pumping and outgassing, by the fact
that it can be carried out at Rotary Vacuum Pump pressures.
These pressures (relative Vacuum) of the range 0.05 to 0.01 torr giving
mean free paths of the order of 1 to 5 mm respectively.
Evaporation under these conditions is not unidirectional as the
particles engage in a number of collisions before they arrive at the
surface, enhancing the possibility of a uniform coating, even on
sculptured surfaces.
