**2.1. Pulsed laser deposition (PLD)**

**1. Introduction**

meaning 'to carry away'.

ablated [9].

and annealing, and laser sputtering.

deposition (CPLD) [10].

beam with solids [2–4], liquids [5], and gases [6].

A low wavelength of the laser beam and a very short pulse (ns‐fs) duration induce instant local vaporizationonthesurfaceofatargetmaterialgeneratingaplasmaplumeconsistingofphotons, electrons, ions, atoms, molecules, clusters, and liquid or solid particles. This phenomenon is known in the literature as '**laser ablation'** [1], a term derived from the Latin word '*ablatio'*,

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

Shortly, after the first laser functionality demonstration in 16 May 1960, numerous theoretical and experimental studies were performed concerning the interaction of the high intensity laser

Laser ablation is the base principle of most applications involving laser processing of materials: precise cutting, hole drilling, laser cleaning of surfaces, compositional analysis, and thin film deposition. The latter came as an obvious application, as a plate/slide/wafer can easily be positioned in front of the plasma plume, acting as a collector for the hot ablated material that condenses in the form of a thin film. This deposition method is known as pulsed laser deposition (PLD). The earliest attempt of thin film deposition was made in 1965 by Smith and Turner [7], but the true breakthrough was achieved by Dijjkamp et al. in 1987 [8], who succeeded the stoichiometric transfer of a compound with a complex molecular structure, very difficult to obtain using other deposition techniques. In this situation, it can be considered that a *congruent ablation* was attained. The decrease in the pulse duration meant laser beams with higher delivered energies that significantly increased the range of materials that could be

Historically, the method was known under several denominations [9]: pulsed laser evapora‐ tion, laser induced flash evaporation, laser molecular beam epitaxy, laser assisted deposition

Some variations in PLD emerged out of necessity to deposit more complex materials or materials degradable at high temperatures. Instead of a single laser beam as in classical PLD, two laser beams can be used simultaneously to ablate two targets mounted on a carousel system, producing a mix of plasmas that will generate thin films with variable composition over the surface. This variation in PLD is known in the literature as combinatorial pulsed laser

Another variation in PLD developed out of necessity to protect compounds with long and fragile molecular chains is called matrix‐assisted pulsed laser evaporation (MAPLE), and it uses as the target, a frozen mix consisting of the active material to be deposited and a buffer

All these variations in PLD will be discussed in detail in the next chapters with relevant ex‐

matrix that preponderantly absorbs the laser beam energy [11].

amples for their advantages and drawbacks.

The material that is irradiated by the laser beam is called the 'target', while the collector is commonly referred to as the 'substrate'. They have to be placed plan‐parallel in a deposition chamber, which is under vacuum conditions. A high intensity laser placed outside the deposition chamber is used as an energy source to ablate the target material and to deposit the thin film. The target vaporization is induced by photons, so no contamination/impurification occurs during the deposition process.

Contrary to this, simplicity of the experimental assembly, the laser‐material interaction, which is the PLD base, is a very complex physical phenomenon that involves a succession of different processes [12]. They are:


If deposition is made in reactive gas and the obtained film has a composition different from that of the target, the name of the synthesis process is reactive pulsed laser deposition (RPLD). The PLD/RPLD set‐up is given in **Figure 1**.
