*2.2.3. Applications*

The synthesis of new materials starting from precursors (i.e., BaF2, SrF2 and TiO2 to form (Ba, Sr)TiO3 [74] or BaF2 and TiO2 to form BaTiO3 [75]); deposition of thin film libraries of doped oxide materials: (Ba1−*x*Sr*x*)TiO3 doped with Ca, W, Cr, Mg, Mn, Y and La [74]; libraries of TiO2 doped with Co [76]; artificial oxide lattices and heterojunctions controlled at an atomic scale [77] (SrTiO3/BaTiO3superlattices); composition spreads: La1−*x*Sr*x*MnO3with 0 ≤ *x* ≤1 [78], Ba1−*x*Sr*x*TiO3 [79], Mg*x*Zn1−*x*O [80] and IZO [81].

### **2.3. Matrix-assisted pulsed laser evaporation (MAPLE)**

For electronic, optical and biosensor device applications, the materials of choice cover poly‐ meric materials for the fabrication and passivation of electronic coatings, organic dye mole‐ cules for non‐linear and optical limiting applications, biocompatible and protein coatings for micro‐array biosensor applications, and living cells for tissue engineering. The ability to deposit various classes of functional polymeric and organic materials using a single technique provides a significant advantage for their development and implementation.

When a laser interacts with an organic target under the usual conditions for PLD, the material, which is grown in a thin film form, is different from the starting material, the functional groups being often altered [11]. The organic chain can also be broken leaving the film to be made up of smaller polymeric pieces and with different functional groups terminating the ends. Even small changes in the number of functional groups or the degree of polymerization can preclude the use of these films for their desired application. Such modifications might be acceptable for some applications, but in general, the use of lasers for depositing thin films of polymeric and organic materials, requires more subtle approaches than those offered by PLD alone.

MAPLE, a laser based vapour deposition technique derived from PLD, has been developed, at the end of 1990s, to deposit thin organic and biologic films without decomposition or other major irreversible damage [82]. MAPLE is a physical vapour deposition technique capable of depositing uniform thin films over a larger area. Specific to MAPLE is the use of a cryogenic composite target made of a dilute mixture of the polymer/ biopolymer/ protein to be deposited and a light absorbent, and high vapour pressure solvent matrix.

The principal objectives that this technique has to perform are:

the sample. From 3 to 6 cm (in respect with the centre of the sample), the ratio continues its

In **Figure 13b**, the evolution of the In/(In+Zn) ratio is presented. Starting from the glass border towards the centre, an ascendant trend from 0.40 to 0.54 is observed. Along a distance of 6.5 cm, the In/(In + Zn) ratio increased by 26%. The results are very similar to the values

The plasma spread is strongly influenced by the atomic weight of the species. For each type of the target material, new complete compositional tests and mapping should be performed on

The synthesis of new materials starting from precursors (i.e., BaF2, SrF2 and TiO2 to form (Ba, Sr)TiO3 [74] or BaF2 and TiO2 to form BaTiO3 [75]); deposition of thin film libraries of doped oxide materials: (Ba1−*x*Sr*x*)TiO3 doped with Ca, W, Cr, Mg, Mn, Y and La [74]; libraries of TiO2 doped with Co [76]; artificial oxide lattices and heterojunctions controlled at an atomic scale [77] (SrTiO3/BaTiO3superlattices); composition spreads: La1−*x*Sr*x*MnO3with 0 ≤ *x* ≤1 [78],

For electronic, optical and biosensor device applications, the materials of choice cover poly‐ meric materials for the fabrication and passivation of electronic coatings, organic dye mole‐ cules for non‐linear and optical limiting applications, biocompatible and protein coatings for micro‐array biosensor applications, and living cells for tissue engineering. The ability to deposit various classes of functional polymeric and organic materials using a single technique

When a laser interacts with an organic target under the usual conditions for PLD, the material, which is grown in a thin film form, is different from the starting material, the functional groups being often altered [11]. The organic chain can also be broken leaving the film to be made up of smaller polymeric pieces and with different functional groups terminating the ends. Even small changes in the number of functional groups or the degree of polymerization can preclude the use of these films for their desired application. Such modifications might be acceptable for some applications, but in general, the use of lasers for depositing thin films of polymeric and

organic materials, requires more subtle approaches than those offered by PLD alone.

and a light absorbent, and high vapour pressure solvent matrix.

MAPLE, a laser based vapour deposition technique derived from PLD, has been developed, at the end of 1990s, to deposit thin organic and biologic films without decomposition or other major irreversible damage [82]. MAPLE is a physical vapour deposition technique capable of depositing uniform thin films over a larger area. Specific to MAPLE is the use of a cryogenic composite target made of a dilute mixture of the polymer/ biopolymer/ protein to be deposited

provides a significant advantage for their development and implementation.

ascendant trend to reach a value of 0.50 at the centre of the film.

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

obtained by EDS investigations on the same CPLD samples [73].

Ba1−*x*Sr*x*TiO3 [79], Mg*x*Zn1−*x*O [80] and IZO [81].

**2.3. Matrix-assisted pulsed laser evaporation (MAPLE)**

*2.2.2. Drawback of CPLD*

the resulting films.

*2.2.3. Applications*


Changing the target to a frozen composite modifies the laser material interaction, so that the major part of the laser energy is absorbed by the solvent molecules and not by the fragile solute. The rapidly evaporating volatile solvent desorbs the fragile solute by soft collisions and deposits it as a uniform thin film whose properties, such as chemical structure and function‐ ality, have been maintained (**Figure 14**). Since the receiving substrate is kept at room temper‐ ature and the sticking coefficient of the solvent is nearly zero, the evaporated solvent is efficiently pumped away by the vacuum system.

**Figure 14.** Schematic of material transfer by MAPLE technique.

The MAPLE target is composed of less than 10 wt% of the film material. Each film molecule is surrounded or shielded by a large amount of matrix. This structure prevents the direct thermal and photonic damage to the film material [83].
