Nanostructure of calcium phosphate films synthesized by pulsed laser deposition under 1 Torr: Effect of wavelength and laser energy

[Display omitted] •High pressure pulsed laser deposition of hydroxyapatite varying wavelength and energy.•Amorphous calcium phosphate thin films were formed using green and infra-red lasers.•Particles decrease in size increasing the infra-red laser energy from 100 to 600 mJ.•Rich Ca/P ratio ring-shaped particles were ejected from the target.•Low Ca/P ratio spherical particles were formed on the way to the substrate. In this study, we investigated aspects about the nanostructure of calcium phosphate films formed by pulsed laser deposition under a high-pressure gas (argon) environment (1 Torr) that are not addressed in the literature by using infrared and green laser sources. The plume generated from an ablated hydroxyapatite target was deposited directly over transmission electron microscopy (TEM) grids during 120 s to allow for the use of TEM techniques to investigate the morphology, composition and structure of deposited films from the micron to the nanoscale. The films were found to comprise five different calcium phosphate structures: (1) unstructured amorphous thin film formed by the deposition of ions and molecules over the substrate, (2) dense nanoparticles (