A porous target will crumble as we all know, and heated porous target will go bad much faster. After every run in PLD, or a couple of runs/ablations, one has to scrape the target, to obtain a fresh surface, and a porous target will worn out fast. Finally the ablation from a porous rough surface can result in some particulate matter getting deposited. So a good highly dense target will last longer, and also provide you good quality ablated material.

There is no question of dielectric breakdown, you are not applying any applied electric field during PLD.

K. Sreenivas

@K. Sreenivas

But Sir, as I was reading the book by Chrisey & Hubler, here it is mentioned that because of the radiation power density falling on the material, a huge electric field will be developed causing dielectric breakdown and hence forming a plasma.

Can you please enlighten me on that?

Reference: Pulsed laser deposition of thin films; Chrisey & Hubler, Page no. 7

I agree with K. Sreenivas, rather than focusing on the dielectric rupture of the material, you should bear in mind that when you focus laser radiation, you are considerably increasing the energy density that you will supply on the material, also, depending on the duration of the laser pulse with hich your system counts, you will also have a very high power density, so that, so much energy delivered in a very short time, you get immediately that the material passes through all the known states of matter to form a plasma. Then, when focused laser radiation hits, it is able to tear not only electrons from their natural state, but complete atoms that will be deposited on a substrate and this is where the importance of having a sufficiently dense target comes from, because the possible microexplosions occurred in the target, there is a risk that this will fall apart, in addition, there is also the possibility of extracting micrometric particles that would damage your experiment. An important thing is also that if the ablation is carried out in regions with different compactness, the physical behavior of the plasma phenomenon would definitely change. If you consider all of these scenarios, having a low density target would cause you to lose some of the benefits of this technique.