**5. Deposition onto ribbon**

**Figure 16.** Target utilization efficiency *η* versus *k*. The dashed line refers to approximation [10].

164 Applications of Laser Ablation - Thin Film Deposition, Nanomaterial Synthesis and Surface Modification

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part of the target and reduced utilization efficiency.

of *η* will not be greater than 0.5.

**4.3. Focal spot in the form of a sector**

the target surface.

One can see that at *k <* 1, it is well approximated by the straight line according to the formula

Thus, we have the simple expression for target utilization efficiency with a sufficiently good approximation. Obviously, for experimentally actual values of *L* and *R* where k < 1, the value

Note that the method suggested in patents [10, 11] has a similar drawback. The cycloidal trajectory described by the focal laser spot on the surface of the target arising due to the rotation around two parallel axes will also result in more intense material evaporation from the central

The consideration of the problem stated above suggests its cardinal solution. In the range 0 *< R < L*/2 where the focal spot is a semicircle, the equality *η* = 1 holds. But a semicircle is the particular case of a sector with the angle of 180°. The scheme of the modified PLD method is shown in **Figure 17**, which simply and cardinally solves the problem on the maximal utilization of the target material. The laser deposition installation is suggested, which differs from ordinary devices by a simple optical system placed outside the deposition chamber. It comprises two lenses and a diaphragm and provides the focal spot in the form of a sector on

If such a focal spot coincides with a sector‐shape area on the target surface and the density of energy is uniform over the focal spot, then the surface of the uniformly rotating target will be uniformly irradiated, which will provide a uniform material ablation from the surface.

=+ » 0.004 0.617 0.6 *k k* (8)

A method of PLD of thickness‐ and composition‐homogeneous thin films on a translationally moving ribbon of up to 100 mm‐width is proposed [11]. The peculiarity of the method is in the matter deposition via a mask placed in vicinity of the substrate. Two configurations of mask slits providing for the thickness homogeneity of films are considered. Exact dimensions of the mask slits are calculated using the data of an angular distribution of mass transfer in a plasma torch.
