**1. Introduction**

The first report of laser ablation generated plasma to deposit a film dates back to 1965, using a continuous ruby laser [1]. As the obtained film quality was inferior to those made with other deposition techniques at that time, the laser deposition remained confidential for two decades. The discovery mid 80's of the high Tc superconductor YBa2Cu3O7-x (YBCO) [2–3] triggered a frantic search for room temperature superconducting cuprates materials, including strong effort for thin film synthesis. The complex cuprate cationic composition makes film growth difficult using conventional physical vapor deposition (PVD) techniques like magnetron sputtering or evaporation. Indeed, to grow films with the right composition it is mandatory to start with a stoichiometric plasma. The Ar+ sputtering rate of multi-cationic targets and the distribution in the plasma strongly depends on the cations mass, which precludes the use of a stoichiometric target to obtain

a stoichiometric plasma. The offset target composition leading to stoichiometric films is unpredictable and a trial-and-error method is usually employed that renders magnetron sputtering an impractical technique for multi-cationic new materials research. Evaporation temperatures depend on the nature of the cations, which make a thermal vaporization of stoichiometric target inappropriate too. The attempt to produce cuprates films using sputtering and evaporation led to poor quality films.

Ceramic target vaporization based on laser ablation does not depend on the nature of the atoms within the target and result in a stoichiometric plasma as long as the energy per surface unit (i.e. the laser fluence) is above the ablation threshold. Venkatesan and co-workers were the first to vaporize an YBCO target using a pulsed excimer laser (UV KrF). After fine tuning the ablation conditions by checking the spatial distribution of the cations they rapidly produced superconducting films having the best physical properties of that time [4]. This first successful synthesis of high Tc cuprates films using a pulsed laser drew the interest of the community and several laboratories started working in the field now known as pulsed laser deposition (PLD). In the following decade, beside cuprates superconductors, strong interest in colossal magneto-resistive manganites and multiferroic ferrites has arisen. This intense scientific activity on multi-cation oxides associated to PLD ease of use, versatility and reasonable cost contributed to its rapid expansion in the 90's.

Since then PLD based thin film research thrived over a wide range of materials, physical properties and applications. PLD has benefited from in-situ real-time characterization tools developed for other deposition technique to mature into an epitaxial film growth method with control at the atomic scale and able to produce heterostructures with sharp interfaces. At the end of the 90's, material scientists considered transposing combinatorial synthesis, a high throughput synthesis method developed by the pharmaceutical industry, to the field of multi-cation oxides research. Combinatorial PLD (CPLD) rapidly emerged, the basic idea being to grow on a single substrate, in a single deposition run, a film with continuous in-plane chemical modulation. In this way, a wide range of chemical compositions are produced within the same sample and can be quickly scanned to identify compounds with optimum targeted properties. Since the new millennium, CPLD has been refined and its field extended to ternary phase diagram exploration. More recently CPLD research field has been extended to a new territory: the exploration of interface compositions in heterostructures with enhanced functional properties a.k.a. Interface Combinatorial Pulsed Laser Deposition (ICPLD).
