Pulsed laser deposition of thin films: elimination of particulates by second laser irradiation

Abstract

Pulsed laser deposition of thin films has besides numerous advantages a major shortcoming which is the presence of particulates of various shapes and dimensions both on surface and inside obtained structures. Indeed, in many key technological applications the use of completely particulates free films is mandatory. We demonstrated that the origin of size and density of particulates depend on specific experimental conditions. Nevertheless, the proper choice of deposition conditions (i.e. ablating laser wavelength and fluence, target-collector separation distance, growing temperature, ambient gas nature and pressure) allows for the decrease under a certain extent of pollution with particulates, but not for their complete elimination. This lecture reports our successful attempts to obtain completely particulates free deposited structures using two synchronized pulsed laser sources. The first, UV laser source was used to ablate the target material. The second, IR laser system was directed parallel to the target surface. The role of the second laser was to heat and vaporize the particulates present in the tail of the plasma ablated by the pulsed UV laser source.