Using Longitudinal Waves Generated by Pulsed Laser
Shocks for Characterization of Films of AlN/Al
J. F. M. C. Pinto1, A. R. Costa1, F. S. L. Cassino1, P-Y. Jouan2, A. Tricoteaux3
1
Rede Temática de Materiais (Redemat)/Universidade Federal de Ouro Preto (UFOP)
2
Institut des Matériaux Jean Rouxel - Nantes– France,
3
Université de Valenciennes et du Hainaut-Cambrésis – France.
The characterization of materials using mechanical waves (longitudinal waves, shear
and surface waves) generated by shock pulsed laser has been used for many years in solids.
This technique can be applied in various situations, such as assessment of porosity in ceramic
materials, in determining the rolling direction and the grain size of metallic materials,
surveying elastic constants, evaluating stress residual, etc. Using the mechanism of confined
plasma source for generating mechanical waves, provided by Nd: YAG pulsed laser, expected
to feature films, aluminum nitride (AlN) deposited on substrates of aluminum (Al) with
different crystallographic orientations and textures, especially considering the adhesion of the
film and the influence of texture and crystallographic orientation of crystals of the Al
deposition. The attenuation of mechanical energy transient and information such as speed of
the waves and the total energy involved are analyzed to evaluate the properties of the AlN
thin film deposited on Al crystals. Influence of crystallographic orientation of Al on the film
deposition associated with these properties.
The AlN films were deposited on substrates of Al according to procedures developed
and described by (Adamczyk, 2008). The substrates (commercial purity aluminum, 10 mm
diameter) were obtained by solidification under appropriate conditions of heat extraction to
obtain
arrays
of
grains
with
different
crystallographic
orientations.
A typical experimental setup with a pulse Nd: YAG laser system and the substrate / film is
shown in figure 1.
Fig. 1: Description of experimental apparatus for the generation and interpretation of mechanical waves within
the system substrate / film.
The photons from the laser pass through a converging lens. The substrate is exactly the
focal length of lens. Longitudinal waves are generated by the confinement of the plasma that
is produced from the interaction of photons with the surface of Al substrate (surface opposite
to the deposited film). This surface is covered by a thin layer of absorbent carbon, to improve
the absorption of photons. After the shock produced by the expanding plasma, a longitudinal
mechanical wave propagates within the system substrate / film and quickly suffers attenuation
effects. The analysis of this phenomenon provides dates for evaluating the mechanical
properties of the components of the system substrate / film. Other interpretations may lead to
assess the quality of adhesion. Once done the conventional characterization (morphology,
mainly via SEM and EBSD) (COSTA, 2009), this characterization form the basis for the
interpretation of acoustic phenomena recorded on the oscilloscope, from the experiment with
the pulsed laser.
Key words: Laser Nd: YAG, mechanical waves, elastic properties.
[1] ADAMCZYK, J., HORNY, N., TRICOTEAUX, A., JOUAN, P.-Y., ZADAM, M., Appl.
Surf. Science, 254, 1744, 2008.
[2] COSTA, A. R.,CASSINO, F. S. L., PINTO, J. F. M. C., JOUAN, P.-Y., TRICOTEAUX,
A., Morfologia e comportamento tribológico de AlN Depositado Sobre alumínio: Influência
da Orientação Cristalográfica do Substrato, In: CONGRESSO ANUAL DA ABM, 64., 2009,
Belo Horizonte. Anais, 2009. 1 CD.
[3] POPOVICS, J. S., disponível em: www.gatewaycoalition.org/files/NewEH/htmls/Popovic.
pdf, Acessado em: 17/08/2009, 09:30h.
[4] ROSA G; OLTRA, R; NADAL, M.-H; Laser induced decohesion of coatings: probing by
laser ultrasonics, Ultrasonics, 40, p. 765–769, 2002.
[5] ROSA, G., PSYLLAKI; P., OLTRA, R., COSTIL, C., CODDET, S., Silmultaneous laser
generation and laser ultrasonic detection of the mechanical breakdown of a coating-substrate
interface, Ultrasonics, 39, p. 355-365, 2001.
E-mail: [email protected]/
Address: Laboratório de Engenharia de Superfícies e Técnicas Afins (LESTA),
Departamento de Engenharia Metalúrgica e de Materiais (DEMET),
Universidade Federal de Ouro Preto (UFOP). Ouro Preto/MG.
CEP.: 35400-000. Tel.: 3559-1103.