Pulsed laser deposition

While the basic setup is simple relative to many other deposition techniques, the physical phenomena of laser-target interaction and film growth are quite complex (see Process below).

The detailed mechanisms of PLD are very complex including the ablation process of the target material by the laser irradiation, the development of a plasma plume with high energetic ions, electrons as well as neutrals and the crystalline growth of the film itself on the heated substrate.

The process of PLD can generally be divided into four stages: Each of these steps is crucial for the crystallinity, uniformity and stoichiometry of the resulting film.

It has been shown that particles with kinetic energies around 50 eV can resputter the film already deposited on the substrate.

This high supersaturation causes a very large nucleation density on the surface as compared to molecular beam epitaxy or sputtering deposition.

Smith and Turner utilized a ruby laser to deposit the first thin films in 1965, three years after Breech and Cross studied the laser-vaporization and excitation of atoms from solid surfaces.

In the early 1980s, a few research groups (mainly in the former USSR) achieved remarkable results on manufacturing of thin film structures utilizing laser technology.

The target material which is evaporated by the laser is normally found as a rotating disc attached to a support.

This special configuration allows not only the utilization of a synchronized reactive gas pulse but also of a multicomponent target rod with which films of different multilayers can be created.

A plume ejected from a SrRuO 3 target during pulsed laser deposition.
The diagram shows the following: A laser beam is by a lens, enters a vacuum chamber, and hits a dot labeled target. A plasma plume is shown leaving the target and heading toward a heated substrate.
One possible configuration of a PLD deposition chamber.
Thin films of oxides are deposited with atomic layer precision using pulsed laser deposition. In this picture, a high-intensity pulsed laser shoots a rotating white disk of Al 2 O 3 (alumina). The laser pulse creates a plasma explosion, visible as the purple cloud. The plasma cloud from the alumina expands towards the square substrate, made of SrTiO 3 , where it condenses and solidifies, building up one atomic layer at a time. The substrate is mounted on a heating plate, glowing red at a temperature of 650 °C, to improve the crystallinity of the alumina thin film.