**1. Introduction**

Pulsed laser deposition (PLD) is a popular application of laser ablation for making thin films. The technology in its variation of the matrix-assisted pulsed laser evaporation (MAPLE) has become a potent way of making polymer and other organic coatings. The chapter will describe a new method of making nano-composite films based on concurrent ablation/evaporation of more than one organic MAPLE and inorganic PLD targets with several laser beams. The advantage is an independent and optimized control of the deposition conditions for each target. The discussion will include the design of the multi-beam multi-target deposition system, examples of the deposited nano-composite films and their properties, the encountered problems/solutions, and the future trends.

For the last three decades, PLD technique has been intensively used for deposition of many kinds of oxides, nitrides, carbides, and metals and for fabrication of thin films including those composed of superconductors, electro-optic BaTi03, piezoelectric ZnO, electro-conductive TiO2, rare earth (RE) doped phosphate glasses, etc [1–14]. Those thin films had many deficiencies that had to be addressed before making them suitable for commercial applications. The technique was used by Smith and Turner [2] in 1965 for the preparation of semiconductor and dielectric thin films. They demonstrated the stoichiometry transfer between the target and the deposited film and high deposition rates of about 0.1 nm per pulse. The occurrence of the droplets of the target material on the substrate surface has been observed in [3]. Despite some encouraging results for single-component films, the conventional single-beam single-target PLD technique remains to be poorly suitable for composite films made of the materials of different nature: one of the reasons that a single laser beam cannot be always suitable for a wide spectrum of materials. Further improvement is a new variant of PLD called the concurrent multi-beam multi-target PLD that deposits different materials simultaneously with different laser beams producing overlapping plumes. In case of polymer nano-composite films at least one of the laser beams and the target must be suitable for the process of deposition of the polymer host, such as MAPLE.

In MAPLE, a frozen solution of a polymer in a volatile solvent becomes a laser target [15–54]. The solvent and concentration of the solution are chosen in such a way that first, the polymer dissolves completely and forms a dilute solution free of particulate; second, the main portion of the laser energy is absorbed by the solvent and not by the solute; and third, no photochemical reaction occurs between the solvent and the solute. The interaction between the laser radiation and matter in MAPLE is a photothermal process. The energy of the laser beam absorbed by the solvent is converted to thermal energy that heats the polymer but causes the solvent to vaporize. As the solvent molecules escape into the gas phase, the polymer molecules gain sufficient kinetic energy via collisions with the evaporating solvent molecules and enter the gas phase as well. Selection of the optimal MAPLE conditions (laser energy and wavelength, pulse repetition rate, type of solvent, concentration of the polymer solution, temperature, and background gas and its pressure) can result in the deposition process with no significant degradation of the polymer. The MAPLE deposition is carried on layer-by-layer, while the concentration of the polymer solution in the ablated target remains constant. When a substrate

is positioned directly in the path of the plume, a film starts forming from the evaporated polymer molecules on a substrate placed in the path of the plume. At the same time, the volatile solvent molecules are taken away from the chamber by the vacuum pump. In case of fabrication of polymer nano-composites, MAPLE targets are usually prepared as nano-colloids of the additives of interest in the initial polymer solutions. Combining the components of different nature, such as polymers and inorganic substances, in the same target and ablating them with the same laser beam rarely results in nano-composite films of fair quality. The laser beam energy and wavelength cannot fit all components in the mixture. Also, the proportion of the components in the film is dictated by the target and cannot be altered in the process. The improvements can be expected in the method of concurrent multi-beam and multi-target deposition using MAPLE polymer targets and inorganic PLD targets, each being concurrently ablated by laser beams of different wavelengths [55–64]. The method can be called as multibeam multi-target MAPLE and PLD or with acronym MBMT-MAPLE/PLD that is described below.
