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@PHDTHESIS{PereraMercado:62059,
author = {Perera Mercado, Yibran Argenis},
othercontributors = {Poprawe, Reinhart},
title = {{D}iamond-like carbon and ceramic materials as protective
coatings grown by pulsed laser deposition},
address = {Aachen},
publisher = {Publikationsserver der RWTH Aachen University},
reportid = {RWTH-CONV-123657},
pages = {IV, 100 S. : Ill., graph. Darst.},
year = {2004},
note = {Aachen, Techn. Hochsch., Diss., 2003},
abstract = {A rather large number of nitride, carbide, and oxide thin
films are used as hard and wear-resistant coatings, for
optical, corrosive, and refractory applications that are of
crucial importance. Additional requirements place even more
stringent conditions on the deposition processes. The
properties of coatings deposited by pulsed laser deposition
are determined by the deposition parameters, the composition
of the PLD plasma and its ionization states, the substrate
conditions, etc.. In this way, the advantageous properties
of PLD can be used with the general aim to increase the
adhesion of the high quality PLD thin films to offer new
applications where the hard, optical, and/or thermal
coatings are required to contribute to surface engineering.
A first objective has been to shine some light on the
optical and mechanical properties of smooth, homogeneous,
and adherent SiNx ceramic coatings which have been deposited
on different substrates such as glass, silicon wafer, tool
steels, and tungsten carbide $(WC-10\%Co)$ at various
processing gas pressures and different laser fluences. The
r.f. plasma and the PLD-plasma using Si3N4 target have been
analyzed during the deposition of SiNx coatings revealing as
well as Si° atoms, Si+ ions, No atoms, and N+ ions with
these species working actively in the dissociative
recombination processes in the nitrogen r.f. and PLD plasmas
to promote the physical and chemical adsorption on the
substrate surfaces and on the nitridation layer to grow
finally the SiNx thin films. Some optical properties
measured from the SiNx coating as the refractive index show
an increase as the nitrogen processing gas pressure
decreases. A general increase in the refractive index is
detected as the laser fluence is increasing. Considering Si
and its compounds as nucleates for diamond and DLC coatings,
SiNx was used as buffer layer to improve the adherence of
DLC hard coatings on metallic and tungsten carbide
substrates. The influence of the substrate materials on the
nucleation and growth of DLC coatings and the adherence of
this superhard coating to different substrates was
investigated. The deposition of DLC coatings on substrates
(tool steels and $WC-10\%Co)$ with high Co-content (known as
an anti-nucleate element for the sp3-bond) has been achieved
by using a polishing process with diamond disk and diamond
solution, and the subsequent chemical etching to produce an
amorphous layer of CoO/CoSO4 which is removed from the
surface by argon r.f. plasma. The DLC coatings with an
application-like mechanical properties are deposited $(60\%$
sp3-content), but a poor adherence is obtained and the
coatings showing spontaneous delamination from the
substrates. By using SiNx coatings as buffer layer the
adherence of the hard DLC films is improved. The process
consisted in the nitridation of the surface by r.f. nitrogen
plasma and a subsequent deposition by PLD of a SiNx ceramic
in nitrogen processing gas pressure directed towards
different substrates such as metals, ceramics, and polymers.
Finally smooth, homogeneous, and adherent DLC coatings on
tool steels and on $WC-10\%Co$ substrates are obtained. The
chemical bonds of the DLC coatings characterized from Raman
spectra and calibrated by EELS, indicate that the
sp3-content in the DLC films increases with increasing laser
fluence, and decreasing processing gas pressure. By
increasing the number of sp3-bonds in the DLC coatings with
the change in the deposition parameters by PLD, the hardness
and Young's modulus increase with a direct improvement in
the mechanical properties. The adhesion of DLC coatings with
a large sp3-content deposited on $WC-10\%Co$ has been
improved. The failure mode is quite different to the DLC
coatings on tool steels, which show an adhesive failure due
to the plastic deformation of the metallic substrates. Based
on the actual demands for stable and nondegradeable
refractory coatings a more general goal is to understand the
crystallization of Al2O3-ZrO2 composite coatings associated
to the PLD deposition parameters and annealing. In the past
the deposition of complex refractory materials and diverse
composites was not possible until recently. Advances in the
pulsed laser deposition technique have now made it possible
to produce such special thin films, which enable a variety
of diffusion and other kinetic studies to be carried out.
The smooth, homogeneous and adherent alumina-zirconia
composite coatings in a relation of 85:15 (Al2O3-ZrO2) are
deposited on silicon wafer, stainless steels, and CMSX-2
substrates with a substrate temperatures up to 800°C
playing no role in the crystallization of the composite
Al2O3-ZrO2 coatings. A homogeneous deposition of amorphous
composite materials can be transformed to more
stoichiometric crystalline coatings by increasing the
kinetic energy supply during the annealing. After annealing
the composite coatings exhibit a higher level of
crystallization of a-alumina and cubic-zirconia with
decreasing oxygen processing gas pressure, and with
increasing the laser fluence, associated to the subsequent
change of the coating thickness at constant
target-substrate-distance, due to the expansion of the
plasma plume and the removal of more particles with the
transfer of energy into the laser-induced plasma.},
keywords = {Siliciumnitrid (SWD) / Impulslaserbeschichten (SWD) /
Dünne Schicht (SWD) / Stoffeigenschaft (SWD) /
Diamantähnlicher Kohlenstoff (SWD) / Aluminiumoxide (SWD)},
cin = {100000},
ddc = {530},
cid = {$I:(DE-82)100000_20140620$},
typ = {PUB:(DE-HGF)11},
urn = {urn:nbn:de:hbz:82-opus-9737},
url = {https://publications.rwth-aachen.de/record/62059},
}
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