ICMCTF 2012! - CD-Lab Application Oriented Coating Development

showed an increase of the oxidation resistance with the silicon content. In
the case of layers with silicon contents between 5 and 8 at.% an oxidation
resistance up to 700°C was observed. At this temperature a weak TiO2
formation occurred at the surface.
Furthermore TiSiCN coatings were deposited using the same titanium and
silicon precursors. The ratios of the silicon precursors to TiCl4 were varied.
Hardness values up to 40 GPa were measured for optimum ratios. The
structure was analysed by SEM, XRD and XPS.
The examination of the adherence of TiSiN and TiSiCN layers showed that
a diffusion barrier is necessary for suppressing the cobalt diffusion from
cemented carbide substrate into the layers. If interlayers of TiN or TiCN
were applied critical loads of 80 N for TiSiN and 50 N for TiSiCN layers
were obtained from scratch test measurements.
10:00am B2-1-7 High temperature chemical vapor deposition of highly
crystallized and textured silicon on metals for solar conversion, O.
Gourmala, R. Benaboud, G. Chichignoud, E. Blanquet, C. Jimenez, B.
Doisneau, K. Zaidat, M. Pons (michel.pons@simap.grenoble-inp.fr),
Grenoble INP, France
Highly crystallized silicon layers were grown on metal sheets at high
temperature (950°C) by thermal CVD from silane. An intermediate buffer
layer (TiN layer) was mandatory to prevent interdiffusion and silicide
formation but also to compensate lattice parameters and thermal expansion
coefficients mismatches between metal and silicon and ideally transfer
some crystalline properties (grain size, texture) from the substrate to the
silicon layer. After a thermodynamic study, intermediate titanium nitride
diffusion barrier was selected and processed by CVD. Special attention is
given to the substrate surface preparation for texture transfer. The structure
and the interfaces stabilities of these silicon/nitride/metal stacks were
studied by FEG and TEM, X-ray diffraction, Raman and energy dispersive
X-ray spectroscopy.
By both optimizing substrate preparation and silicon processing conditions,
this multilayered structure could be able to provide an efficient and reliable
converter, comparable with classical crystalline silicon wafers in terms of
solar conversion yield, while overcoming their majors drawbacks: due to
ingot sawing and squaring as well as wafer slicing.
10:20am B2-1-8 In-line Deposition of Silicon-based Films by Hot-Wire
Chemical vapor Deposition, L. Schäfer
(lothar.schaefer@ist.fraunhofer.de), T. Harig, M. Höfer, A. Laukart,
Fraunhofer IST, Germany, D. Borchert, Keipert-Colberg, Fraunhofer ISE,
Germany, J. Trube, Leybold Optics GmbH, Germany
Silicon-based films such as hydrogenated amorphous (a-Si:H), and
nanocrystalline silicon (µc-Si:H), and hydrogenated amorphous silicon
nitride (a-SiNx:H) were deposited by hot-wire gas phase activation (HW-
CVD). To evaluate the opportunities of the HW-CVD technology for thin
film deposition in solar industry an in-line hot-wire CVD system was used
to deposit a-Si:H films for passivation of crystalline solar cells as well as for
the fabrication of thin film silicon solar cells. The HW-CVD system
consists of seven vacuum chambers including three hot-wire systems with
maximum deposition areas of 500 mm by 600 mm for each hot-wire
activation source. The deposition processes were investigated by applying
design of experiment methods to identify the effects and interactions of the
process parameters on the deposition characteristics and film properties.
The process parameters investigated were silane flow, pressure, substrate
temperature, film thickness, as well as temperature, diameter and number of
wires, respectively. Growth rates up to 2.5 nm/s were achieved for a-Si:H
films. Intrinsic a-Si:H films for passivation of different crystalline solar cell
types yielded carrier lifetimes of more than 1.000 µs for film thickness
values below 20 nm. Films with thickness values of about 350 nm show
microstructure factors of less than 0.1 measured by FTIR and
photosensitivity ratios of up to 10 6 . For n-doped a-Si:H films prepared with
PH3 as dopant gas specific electrical resistances are in the range of 10 2 Ohm
x cm. P-doped a-Si:H films prepared with B2H6 as dopant gas show
electrical resistances of about 10 5 Ohm x cm. The results of these
investigations are not only aiming at the passivation of crystalline solar cells
but also at the application of hot-wire CVD processes for the fabrication of
heterojunction solar cells as well as thin film silicon solar cells.
10:40am B2-1-9 Oxidation Resistance of Graphene Coated Metal
Films: A Protective Coating, PramodaKumar. Nayak, Chan-Jung. Hsu,
National Cheng Kung University, Taiwan, S.C. Wang, Southern Taiwan
University, Taiwan, JamesC. Sung, KINIK Company, Taiwan, Jow-Lay.
Huang (jlh888@mail.ncku.edu.tw), National Cheng Kung University,
Taiwan
The requirement of protective coating to prevent refined metals from
reactive environments is very important in industrial as well as in academic
applications. Most of the conventional methods used for this purpose
introduce several negative effects including increased thickness and changes
Thursday Morning, April 26, 2012 74
in the optical, electrical and thermal properties of the metal. In this paper,
we demonstrate the coating of graphene films using methane as carbon
source by chemical vapor deposition to protect the surface of Ni substrates
from air oxidation. In particular, graphene prevents the formation of oxide
on the metal surface and protect it from reactive environment. Two methods
are adopted to induce oxidation on the graphene coated Ni surface: i.e. by
heating the specimen in air for several hours and then, by immerging into a
solution of 31% hydrogen peroxide (H2O2). The specimens have been has
been characterized by X-ray diffraction, Optical micrograph, Raman
spectroscopy, X-ray photoelectron spectroscopy, and the results indicate
that oxidation resistance of graphene coated Ni films is only effective up to
a maximum temperature of 500º C in air. It is also observed that graphene
provides effective resistance against H2O2. The results have been compared
with that of graphene coated Cu films in literature. The detailed analysis of
graphene as oxidation resistance against air and H2O2 has been presented.
11:00am B2-1-10 Highly chemically reactive AP-CVD coatings:
Influence of the deposition parameters and application for thermally
reversible interfacial bonding., M. Moreno-Couranjou
(moreno@lippmann.lu), A. Manakhov, N.D. Boscher, Centre de Recherche
Public - Gabriel Lippmann, Luxembourg, J.J. Pireaux, University of Namur
(FUNDP), Belgium, A. Choquet, Centre de Recherche Public - Gabriel
Lippmann, Luxembourg
In this work, we present the plasma copolymerization of Maleic Anhydride
(MA) and Vinyltrimethoxysilane (VTMOS) performed in an Atmospheric
Pressure-Dielectric Barrier Discharge process for the formation of highly
reactive anhydride functionalized coatings.
In the first part of the presentation, we will show how the tuning of the
electrical parameter led to coatings with different combination of
anhydride/carboxylic group surface density, morphology and deposition
rate. For that goal, the power (P) delivered by the source was varied from
50 to 150W. Moreover, the discharge electrical mode was operating in a
continuous wave or a pulsed wave with a pulse ON-time (ton) fixed at 10ms
and a pulse OFF-time (toff) ranging from 10 to 60ms. The different coating
chemistries have been studied by XPS for the estimation of the
anhydride/carboxylic surface density and by ATR FT-IR to investigate the
conservation or the destruction of the cyclic anhydride group related to the
incorporation of the MA monomer in the coatings. The average power (Pav),
defined as Pav=P.[ton/(ton+toff)], appeared as a key parameter to control the
anhydride surface functionalization within a range of 2 to 13 at.%,
independently of the coatings morphology or deposition rate.
In the second part, we will present how the coatings reactivity has been
exploited for the elaboration of a thermally reversible interfacial bonding
property based on a Diels-Alder reaction. For that, MA-VTMOS deposits
have been performed on a rigid polished aluminium and on a kapton foil
and subsequently, treated through a chemical gas phase reaction for the
grafting of the required diene and dienophile groups. The complete
chemical path reaction will be exposed with some adhesion results dealing
with the Diels-Alder and the retro-Diels-Alder reactions.
11:20am B2-1-11 Optical properties of the ZnO thin films grown on
glass substrates using catalytically generated high-energy H2O, E.
Nagatomi, S. Satomoto, M. Tahara, T. Kato, K. Yasui
(kyasui@vos.nagaokaut.ac.jp), Nagaoka University of Technology, Japan
Zinc oxide (ZnO) is useful for many applications such as transparent
conductive films in solar cells and flat panel displays, optoelectronic
devices operating at short wavelengths. Despite the advantages of MOCVD
for industrial applications, ZnO film growth by conventional MOCVD
consumes a lot of electric power to react the source gases and raise the
substrate temperature. To overcome this, a more efficient means of reacting
oxygen and metalorganic source gases is needed. In addition to the low
reaction efficiency, conventional CVD methods yield low-quality ZnO
films, due to incomplete reaction of metalorganic source gases with oxygen
source gases in the gas phase. If thermally excited water is used to
hydrolyze the metalorganic source gases, however, reactive ZnO precursors
are produced in the gas phase, allowing growth of ZnO films under energysaving
conditions.
In this study, we present a ZnO film growth on glass substrates aiming at
the application for transparent conductive thin films, using the reaction
between dimethylzinc (DMZn) and high-energy H2O produced by a Ptcatalyzed
H2-O2 reaction. CVD apparatus is comprised of a catalytic cell
with a fine nozzle, gas lines for H2, O2 and DMZn supplies, and a substrate
holder. H2 and O2 gases were admitted into a catalyst cell containing a Ptdispersed
ZrO2 catalyst, whose temperature increased rapidly to over 1300
K due to the exothermic reaction of H2 and O2 on the catalyst. The resulting
high-energy H2O molecules were ejected from the fine nozzle into the
reaction zone and allowed to collide with DMZn ejected from another fine
nozzle. ZnO films were grown on glass substrates at 573-873K and the film
properties were evaluated.