**2. Main solutions for depositing large‐area films**

Let us briefly consider the main existing ways for large area films deposition [1]. In one of them, a laser beam is incident on a rotating target, before which a rotating substrate is located parallel to the target. The substrate axis is shifted with respect to the plasma plume axis by some distance (**Figure 1a**). This distance is determined by the width of the gap between the target and the substrate, the substrate diameter, and the angular distribution of evaporated particles in the plasma plume. Thus, the part of the plasma plume that is characterized by a higher mass transfer of evaporated material arrives at the substrate edge, where a larger area must be coated for the same time; as a result, a film of uniform thickness grows. A modification of this technique is the version shown in **Figure 1b**. Here, the substrate simultaneously rotates and moves in the horizontal plane. A computer controls the horizontal displacement velocity of the substrate in such a way that the plasma plume axis is directed toward the substrate edge for a longer period as compared to the center.

develop new approaches and solutions for the preparation of large‐area homogeneous in composition and thickness thin films and coatings of complex compounds. PLD turned out to

PLD is used to grow thin films of metals, oxides, polymers, biocompatible materials, and so on. It allows the fabrication of ultra‐thin epitaxial single‐crystalline, polycrystalline and amorphous films, heterostructures and nanocrystalline coatings [1, 2]. PLD is simple in application and, therefore, is widely used in research laboratories. However, it is also prom‐ ising for various commercial applications, in particular, growth of large‐area films. Films of uniform thickness on large‐diameter substrates are necessary for many applications in

Wide use of PLD in the growth of large‐area films is impeded by the following circumstance: the angular distribution of the mass‐transfer rate in the plasma plume formed by laser radiation is nonuniform. Therefore, using conventional laser deposition, one cannot obtain films of uniform thickness on substrates larger than 10 mm in diameter. In this chapter, we describe some main solutions to this problem and propose a new technique for depositing thin films of uniform thickness on large‐area substrates the size of which is limited by the deposition

All versions of PLD of large‐area films are based on the fact that the angular distribution of the mass‐transfer rate in a plasma plume is set by the function *F*(*θ*) = *A*cosm *θ* [1], where *θ* is the angle of deviation from the perpendicular to the target plane. The plasma plume axis, that is, the direction in which the mass‐transfer rate is maximal, is perpendicular to the target surface in a wide range of variation in the angle of incidence of laser beam on the target. Knowing the angular distribution of the mass‐transfer rate of the material evaporated from the target, one can arrange the mutual position and motion of the target and substrate to provide identical amount of evaporated material per substrate unit area over the substrate

Let us briefly consider the main existing ways for large area films deposition [1]. In one of them, a laser beam is incident on a rotating target, before which a rotating substrate is located parallel to the target. The substrate axis is shifted with respect to the plasma plume axis by some distance (**Figure 1a**). This distance is determined by the width of the gap between the target and the substrate, the substrate diameter, and the angular distribution of evaporated particles in the plasma plume. Thus, the part of the plasma plume that is characterized by a higher mass transfer of evaporated material arrives at the substrate edge, where a larger area must be coated for the same time; as a result, a film of uniform thickness grows. A modification of this technique is the version shown in **Figure 1b**. Here, the substrate simultaneously rotates and moves in the horizontal plane. A computer controls the horizontal displacement velocity of the substrate in such a way that the plasma plume axis is directed toward the substrate edge

be a very convenient tool to obtain thin films of high‐temperature superconductors.

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

microelectronics, optical industry, and other modern technologies.

chamber dimensions only.

surface and thus grow films uniform in thickness.

for a longer period as compared to the center.

**2. Main solutions for depositing large‐area films**

**Figure 1.** Schematics of the main techniques for depositing large‐area films: (a) "off‐axis" deposition, (b) deposition on substrate that simultaneously rotates and moves in the horizontal direction, and (c) scanning the laser beam on the surface of a large target.

The drawback of the first version (**Figure 1a**) is the spatial confinement of the ablation plasma plume. Substrates whose diameter exceeds some limiting size are not overlapped completely by the plume region where the mass‐transfer velocity is sufficiently high. This drawback can be compensated for by mounting the substrate at a larger distance from the target; however, the larger the substrate, target distance, the lower the deposition rate. In addition, the stoichi‐ ometry of multicomponent films can be preserved only in certain range of variation in the substrate—target distance.

The drawback of the second version (**Figure 1b**) is the necessity of preliminary analysis of the angular distribution of the mass‐transfer rate in the plasma plume in specific geometry and under specific deposition conditions. In turn, the angular distribution of the mass transfer may vary during deposition, because it depends on several parameters, which may also vary during long‐term deposition. There are many modifications of the above‐described techniques. Some achievements in growing large area films by PLD were described in the study of Eason [2]. As previously, the main technique is based on scanning the laser beam on the surface of a large target (**Figure 1c**). However, the manufacture of a large target for some of the compounds can be very expensive.
