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ENEA - Fusion division
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Thin Film Deposition Laboratory: E-Beam
View of silver in the crucibleduring film deposition
In the e-beam evaporation technique an electron beam is produced by the emission of electrons from an incandescent filament of tungsten by thermo-ionic effect. The filament acts as a cathode and is connected to the negative terminal of a voltage generator, while the anode is constituted by the crucible where the material to be deposited is placed. The crucibles are realized with copper and they are cooled by a water circuit in order to protect them from high temperatures and to avoid the contamination of the evaporating material. The beam electrons, because of the bumps with the target’s atoms, transfer their kinetic energy into thermal energy. Depending on the beam energy , temperatures of 3500°C can be reached, and for this reason such a technique allows the evaporation of a wide class of materials.
The e-beam deposition experimental system is composed by a vacuum chamber which is connected to a pumping system made of a series of a turbomolecular and rotative pump. Inside the vacuum chamber, the anode is constituted by many crucibles separated by a screen in order to allow the subsequent evaporation of different materials. The sample holder is equipped with a heater and a thermoregulator that controls the thermal ramps and the stability of temperature during the deposition.
10KW plant for e-beam deposition
3kW plant for e-beam deposition
In the laboratory there are two different systems for e-beam deposition. The first one, with maximum power of
3Kw, is mainly used for studying purposes; the second, with 10Kw of maximum power, is used for reel-to-reel deposition of buffer layer structures for YBCO based superconducting tapes.
The second (and most recent) system allows to change the position of the incident electronic beam in order to sweep a larger target surface and consequently to increase the deposition rates, it is also equipped with a two reels winding system in order to allow the potential production of reel-to-reel tapes.
SEM image of a YSZ film depositedin a continuous process
Here is a Scanning Electron Microscopy (SEM) image of a YSZ film (Yttria-Stabilized-Zirconia), deposited in a continuous process on a Ni-W metallic tape. In the detail the typical morphology of the YSZ, linked to the deposition technology, can be seen.
SEM image of an YBCO filmcross-section
The efficiency of the continuously deposited buffer layer structure has been verified by growing YBCO films trough PLD on a CeO2-YSZ-CeO2 buffer layer structure whose cross-section can be seen in the right image.
Transport measurements on this samples gave critical current values of 1MA/cm2 at 77K and zero field.
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