**2.1. Multi-beam multi-target MAPLE/PLD system**

The design of the MBMT-MAPLE/PLD system (it is a three-beam and three-target variant) is schematically presented in **Figure 1**. Three laser beams of different wavelength evaporate/ ablate concurrently three targets made of different materials (organic or inorganic). The laser beams are forced to scan over the targets with oscillating (in X and Y directions) reflectors in order to eliminate pre-mature target erosion and cracking due to laser-induced target ablation in a single spot. The photograph of the 24″ vacuum chamber of the system at Dillard University and one of three laser beam guides is presented in **Figure 2**.

**Figure 1.** The schematic of the MBMT-MAPLE/PLD system [60].

**Figure 2.** View of the 24″ vacuum chamber of the three-beam MBMT-MAPLE/PLD system at Dillard University (a). The side view of one of the laser beam guides including the holder for the laser beam scanner attached to the optical window of the chamber (b) [60].

**Figure 3.** Schematic of the target tilting sub-system of the MBMT-MAPLE/PLD system with remote control of the directions of the plumes. Shown are two targets out of three. *θ* is the optimal angle between the plums at which they overlap in point A on the surface of the substrate.

The MBMT-MAPLE/PLD system has a sub-system of the plume direction control schematically presented (for two targets for the sake of simplicity) in **Figure 3**. Remotely controlled vacuum compatible linear actuators tilt the targets in order to achieve an optimal angle *θ* between the plumes (which are perpendicular to the target surfaces) at which the plumes overlap on the surface of the substrate. This secures the uniform mixing of the materials from the targets in the resulting composite film during the deposition process. The photographs of the tilt control sub-system for three targets are presented in **Figure 4**. One important feature of this sub-system is that the target holders are tilted around the axes in the horizontal plane instead of vertical plane, which reduces chances of dropping or spilling the target material.

**Figure 2.** View of the 24″ vacuum chamber of the three-beam MBMT-MAPLE/PLD system at Dillard University (a). The side view of one of the laser beam guides including the holder for the laser beam scanner attached to the optical

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

**Figure 3.** Schematic of the target tilting sub-system of the MBMT-MAPLE/PLD system with remote control of the directions of the plumes. Shown are two targets out of three. *θ* is the optimal angle between the plums at which they over-

window of the chamber (b) [60].

lap in point A on the surface of the substrate.

**Figure 4.** View of the three-target holder with remotely controlled tilt of each target (to achieve overlapping of the plumes on the substrate) (a) and the view of the three-target holder installed inside the vacuum chamber (b).

The target holders of the triple-target sub-system are designed to accommodate MAPLE targets cooled with flowing liquid nitrogen (LN) as presented in **Figure 5**. A copper container for a polymer solution (MAPLE target) is mounted on a copper container for LN (the cooler) that cools the polymer solution (the target) and keeps it frozen. The MAPLE target assembly is connected to the LN feeding and collecting lines (copper tubing) drawn through a flange to be attached to the vacuum chamber. The feeding line is connected to the LN feeding vessel external to the vacuum chamber. The collecting LN line is connected to another external vessel where the LN flows in after passing through the cooler. The MAPLE target assembly is mounted on the top of one of the tilting target holders (**Figure 4**) installed inside the vacuum chamber. Horizontal orientation of the MAPLE target in this design makes possible to conveniently install the empty copper cup in the chamber and fill it later with the liquid polymer solution without the risk of spilling it out before freezing.

**Figure 5.** View of the MAPLE target assembly removed from the vacuum chamber. The target is cooled with liquid nitrogen (LN).
