Thin Film Deposition Using Excimer Lasers
Brant Campbell, Idaho State University
Advances in laser technology have led to the creation of a high power ultraviolet
laser. The excimer laser operates on the same basic premise as other
types of lasers, but has some very distinct differences in how lasing is achieved.
An excimer is a diatomic molecule that only exists in an excited state.
In an excimer laser, a large electrical discharge excites gases in a chamber
in such a way that they will combine to form a stable molecule in an excited
state. The molecule then decays to the ground state by emitting a characteristic
photon and the molecule dissociates. The UV photons emitted have an
energy greater than the binding energy of many molecules and can therefore
be used to break apart molecules. The plume created by the laser pulse
can be directed onto a substrate and the particles from the target will be
deposited onto the substrate. This process is called pulsed laser deposition
(PLD). PLD can be used to create thin films on many types of materials
useful in modern technology. One tool used to analyze thin films created
by PLD is the atomic force microscope (AFM). The AFM uses a cantilever
with a very small tip to characterize the nature of the substrate surface.
This results in a two or three dimensional representation of the thin film
being scanned. With appropriate software, a very detailed roughness
analysis can be obtained, including quantities such as total surface area,
maximum, minimum, and average height of the surface, and average thickness.
This technique is important for many areas of research including integrated
circuits and optoelectronics, micromechanics, and medical implants.