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Fig. 18. First experimental results. (A) Interdigitated electrodes structure. Arms are
interleaved so that between each couple of them there is a strain in the PZT layer. (B)
Detail of the electrodes structure. Sizes are in the range of micrometers because the res-
olution limit of our lithography process is 2um. (C) SEM image of a PZT layer. Its grain
structure is clearly visible. (D) SEM image of a FeTb film. The surface is pretty rough.
Magnets Fabrication. To fabricate magnets we firstly experimented Electron
Beam Lithography (EBL). However we were not able to obtain magnets with
the required resolution with this technique, due to the small dimensions to
achieve and to the vicinity of the desired structures. In the case of small and
close packed features, the proximity effect represents one of the hardest limits
to overcome. The reason lies probably in this reason, in the relative low accel-
eration voltage of our FEI Dualbeam Quanta 3D (30 kV) and the high insulat-
ing nature of the PZT substrate, which generates many interferences with the
electron beam. We therefore switched to Focus Ion Beam (FIB) lithography,
obtaining far better results, some of them are shown in 19 . Figure 19 (A) shows a
simple couple of magnets. The smallest obtainable gap among magnets is around
30-50 nm, but the minimum magnet size is around 65
135 nm 2 , as shown in
Fig. 19 (A). Maintaining the magnets sizes between 100 nm and 200 nm the FIB
lithography is not critical and at the same time is su cient for the construction
of the demonstrator. Both our theoretical analysis and the results presented in
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