ICMCTF 2012! - CD-Lab Application Oriented Coating Development

9:40am B3-1-6 Compressive stress generation and atom incorporation
during growth of low-mobility materials, G. Abadias
(gregory.abadias@univ-poitiers.fr), A. Fillon, A. Michel, C. Jaouen, Institut
P' - Universite de Poitiers, France
The incorporation of growth-induced defects from energetic deposited
particles during sputter-deposition, known as the “atomic peening” effect, is
revisited in low-mobility material thin films by combining in situ and realtime
wafer curvature and ex situ X-ray diffraction techniques.
A series of metastable Mo1-xSix solid solution films were deposited by
magnetron sputtering at low pressure (0.12 Pa) in Ar plasma discharge onto
crystalline (110) Mo template layers. Unbalanced magnetron configuration
and substrate bias voltages up to -120V were used to increase the
contribution of energetic ions to the total deposited energy. The stress
evolution was monitored in real-time using a multiple-beam optical stress
sensor (MOSS) designed by kSA and implemented in the deposition
chamber. The stress-field was determined from XRD using the sin 2 ψ
technique adapted for the case of textured/epitaxial layers. Post-growth ion
irradiation using 310 keV Ar + ions at low dose(< 0.2 dpa) were carried out
to identify the nature of point-defects and associated stress field.
Compressive stress evolution due to atomic peening is observable only
above a first critical energy threshold. The stress-field appears in that case
fully biaxial. Grain-size dependence of stress confirms that defect creation
is confined to the grain boundaries. Further increase of the deposited
energy, above a second threshold, results in the creation of additional
volume defects inside the grains, i.e. expansion of the unit cell. Examination
of sin 2 ψ plots evolution on irradiated films shows that defects incorporated
in the grain boundaries are stable, while those created inside the grain are
highly unstable.
In a deposited-energy/composition space diagram, these thresholds depict
the existence of biaxial or hydrostatic stress domains related to these two
distinct defect creation mechanisms. The strong variation of the critical
energy thresholds with the Si content points out the sensitivity of defects
creation to the intrinsic properties of the material.
10:00am B3-1-7 Variation of substrate biasing and temperature and
their influence on the crystal orientation of γ-Al2O3 films, M. Prenzel
(marina.prenzel@rub.de), A. Kortmann, A. von Keudell, Ruhr Universität
Bochum, Germany
Temperature and substrate bias play a key role in the structural evolution of
aluminium oxide (Al2O3) during the deposition process. On the one hand,
crystallinity depends on the mobility of the particles in the growing film,
which is influenced by the substrate temperature. On the other hand, correct
tailoring of the substrate bias allows to selectively control the energy
distribution function of the ions impinging on the substrate (IEDF). Thus,
film characteristics such as hardness, adhesion, crystallinity, or wear
resistance can be controlled. In this work, manipulation of the substrate bias
is performed by variation of the frequency, amplitude and shape of the
applied bias signal. We will show how different bias functions affect the
shape of the IEDF while keeping the mean energy constant at 55 eV, and
how this in turn has a clear influence on the crystallinity of the film.
The films are deposited in a RF magnetron discharge, driven by 13.56 MHz
and 71 MHz. The target is mounted on the powered electrode and a silicon
substrate is placed on a biased electrode at the opposite side.
Our previous experiments have already shown a preferred orientation in the
film when using a rectangular pulsed bias with 1 MHz frequency and an ontime
of 5 µs. Here, we will present a thorough investigation of how
variations in frequency and duty cycle in the bias signal affect the IEDF and
film properties for constant mean energy and an on-time of 5 µs.
Additionally, the influence of growth temperature (500 °C, 550 °C and 600
°C) will be shown.
Film characterization is performed using FTIR and XRD to determine the
orientation/crystallinity of the films. The measurements are correlated with
the measured and simulated IEDFs in each case. We will show how the
tailoring of the IEDF through bias shape manipulation is excellent tool for
controlling film structure.
The work is funded by DFG within SFB-TR 87.
10:20am B3-1-8 High-Voltage Positive Nanopulse Assisted Hot-
Filament CVD Diamond Growth, M. Takashima, N. Ohtake
(ohtaken@mech.titech.ac.jp), Tokyo Institute of Technology, Japan
In this study, extremely short pulse, whose pulse width was about 50 ns and
called "nanopulse", assisted hot-filament chemical vapor deposition method
was used for the diamond synthesis, and depositions at low substrate
temperature below 500 °C were attempted decreasing filament temperature
and using high-voltage nanopulse assist. In addition, characteristics of
nanopulse plasma were investigated through optical emission spectroscopy
(OES) analysis as well as time resolved optical emission spectroscopy
(TROES) analysis. Spectrometer used was special and the time resolution of
10 ns was enough to trace nanopulse plasma and investigate the effects of
nanopluse on diamond growth.
As a result, we had succeed in depositing diamond at the substrate
temperature of 400 °C using 1500 °C filament and high-voltage nanopulse
assist. Moreover, according to OES and TROES measurements of
nanopulse plasma, the relations between diamond properties and deposition
conditions were found. Atomic hydrogen played an important role on
diamond growth and the diamond was able to be deposited with sufficient
concentration of CH radicals at the afterglow of nanopulse plasma.
Coatings for Biomedical and Healthcare Applications
Room: Sunset - Session D2-1
Coatings for Biomedical Implants
Moderator: R. Hauert, Empa, Switzerland, J. Piascik, RTI
International, US
8:00am D2-1-1 Functional plasma polymer films engineered at the
nanoscale for biomaterial applications, K. Vasilev
(krasimir.vasilev@unisa.edu.au), University of South Australia, Australia
INVITED
Functional coatings presenting a variety of functional chemical groups can
be readily prepared by plasma polymerisation in an easy one-step process.
Applications of such films span over a range of fields from modification of
biomaterials to protective coatings.
In my talk, I will present recent developments from our group on various
biomaterial coatings prepared by plasma polymerisation which include
chemical and biomolecular gradients, and antibacterial coatings based on
silver nanoparticles and conventional antibiotics.
Surface gradients have become important tools for studying and guiding
cellular responses such as migration, adhesion, differentiation, etc. We
generate gradients of various surface chemistries via plasma copolymerisation
over a moving mask. We used these chemical gradients to
direct differentiation of kidney (KSC) and embryonic stem cells. We found
that KSC express proximal tubule markers at medium amine group surface
concentration and adapt a podocyte-like morphology at high.We extended
these surface chemical gradients to density gradients of bound ligands,
proteins and nanoparticles. We developed gradients of two proteins because
gradients of single protein (employed in cell studies up to now) are
probably too simplistic to mimic natural biological processes. We also
developed density gradients of nanoparticles to use as a tool to study the
effect of nanoscale surface features on cell behaviour.
Antibacterial coatings are important for many biomedical applications. We
developed unique coatings based on silver nanoparticles which allow
control over the rate of release of silver ions. As we show, the rate of silver
release can be tuned such that it allows normal adhesion and spreading of
mammalian cell and preserves the antibacterial properties of the coatings.
We also developed two platforms for release of conventional antibiotics
such as vancomycin and levofloxacin. Delicate control over the rate of
release was achieved by a plasma polymer overlayer of a controlled
thickness.
References:
K. Vasilev et al “Tunable antibacterial coatings that support mammalian
cell growth” Nano Lett 10 (1), 202–207 (2010)
K. Vasilev et al “A PEG-density gradient to control protein binding:
creating gradients of two proteins”, Biomaterials 31, 392–397 (2010)
S. Simovic, D. Losic and K Vasilev “Controlled drug release from
mesoporous materials by plasma polymer deposition” Chem Commun 46,
1317 - 1319 (2010)
R.V. Goreham, R. D. Short and K. Vasilev “A Novel Method for the
Generation of Surface-Bound Nanoparticle Density Gradients” J Phys
Chem C 115 (8), 3429-3433 (2011)
8:40am D2-1-3 Effect of the surface atom ordering on the protein
adsorption, P. Silva-Bermudez (suriel21@yahoo.com), L. Huerta, S.E.
Rodil, Instituto de Investigaciones en Materiales, Universidad Nacional
Autónoma de Mexico, México
The study of the protein adsorption is relevant to understand the interactions
biological media–foreign material since the adsorbed protein layer on the
material surface mediates the interactions cell-material, greatly determining
the biological response. The protein adsorption on solid surfaces is mainly
driven by the surface properties; different studies have shown that
properties such as hydrophobicity or roughness influence protein
adsorption. Also, certain crystalline phases of a material have been
129 Friday Morning, April 27, 2012