consists of two interpenetrating networks, one is atomic
scale diamond like (carbon network) a-C:H, another is quartz like (silicon
network) a-Si:O. In carbon network, mainly consist of sp3 hybridization, i.e.
diamond like bonds and chemically stabilized by
“H” atoms. In silicon network, Si atoms are
chemically stabilized by “O” atoms 1. Fourier
transform–infra red (FT–IR) spectroscopy, transmission electron microscopy
(TEM) and X-ray diffraction (XRD) reveal the structural characterization of
DLN. Due to the presence of Quartz like Oxygenated Silicon network (a-Si:O), it
is found that DLN has good adhesion property compare to its predecessor DLC and
hence it is suitable to coat almost any type of materials 2. Due to the
interpenetrating network of hydrogenated carbon and oxygenated silicon, the
internal stress is reduced and thus DLN composite shows good tribological
performance over its predecessor Diamond-like carbon or DLC.
or graphait-like are the umbrella terms
which refer to different forms of amorphous carbon that exhibit some of the unique properties
of natural diamonds or graphit and that can be synthesized in the lab
environment. Diamond-like carbon or DLC is a amorphous hydrogenated carbon which
is a blend of sp2 bonded carbon atoms
into sp3 bonded carbon clusters. In
DLC atomic structure, hydrogen
can be present with an atomic
concentration ranges from 0% – 50%. DLC acronym was first used by Aisenberg and Chabot 3 who for the first
time synthesized amorphous carbon films exhibiting some of the unique
characteristics of natural diamond. Beauty of
the DLC film is that, its properties can
be tailored based on the concentartion
of sp2 – sp3 bonded carbon atoms and hydrogen concentration. Due to the room temperature
deposition possibility, almost all materials those are compatible
with vacuum environment can be coated with DLC films. Unique and tunable properties of
DLC are: material hardness, low friction and high wear resistance, chemical inertness, optical transparency
(visible light – infrared light), thermal conductivity, electrical resistivity,
radiation resistance etc. Most of the present industrial applications of DLC
films are protectitve coating but this application can be extended upto ” data
to beer storage” 4, 5. Properties of DLC films can be controlled further by
doping them with different chemical elements or compunds. Thus a new class of amorphous hydrogenated carbon is
formed whose atomic morphology complies with crystalline diamond and wisely
termed as Diamond-like nanocomposites. In this process, some properties of DLN
films are improved even further than DLC films. DLN
coating have been in existance since early 1990s. V.F. Dorfman first reported
and synthesized this unique class of material 1. Later on Bekaert Advanced Coating Technologies (formerly known as
Advanced Refractories Technologies) and Russian and American scientists
patented DLN coatings for various protective coatings applications 6, 7, 8, 9,
10, 11, 12, 13, 14, 15. DLN coatings also have been used in
micro-electromechanical systems (MEMS) applications like LIGA (German acronym
for Lithographie, Galvanoformung und Abformung) structures 16 and more 17.
Bekaert Advanced Coating Technologies, Belgium have used plasma enhanced
chemical vapor deposition (PECVD) method for growing such composite films.
Chinese researchers have successfully used ion beam technology for growing DLN
films 18. South Korean researchers have reported thermally activated CVD process
for growth of DLN films 19. Moreover Diamond-like carbon/nanosilica composite
films have been deposited on silicon substrates, making use of the electrolysis
of methanol– dimethylethoxydisilane (DDS) solution at low temperature 20. DLN
was deposited with same type of reactor, used by Bekaert Advanced Coatings
Technology, Belgium by a research group
to deposit the thin film over Co-Cr alloy based knee implant of complex shape
Various researchers have
recorded various unique characteristic of DLN thin film since its inception.
They have focussed different properties in their research works 21, 22, 23,
24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42.
DLN coating have excellent bulk and surface property as well as thermal
stability. This can be used as tribological coatings, chemical protective
coatings 43, 44, 45, 46, 47, 48 and abrasion resistant coatings. It has
optical transparency over a wide bandwidth which includes visible light and
infrared. Due to this reason, DLN coating is used as antireflection coating
over the solar cell to enhance the over all efficiency of the system. Due to low residual stress DLN coating has
excellent adhesion to variety of substrate materials 31, 33. Researchers at
Department of Cardiology, University Hospitals Leuven, Belgium 49 reported the biocompatibility of DLN film
resulting in decreased thrombogenicity and decreased neointimal hyperplasia.
Awadesh Kr Mallik et al reported that deposition of DLN coating by PECVD method
over different substrate used as load bearing orthopedic implant and the result
was satisfactory 2.
Since its inception, DLN
films are being received huge attention due to its attractive electrical mechanical
optical and tribological properties such as reduced stress level, increased
thermal stability, high hardness, low friction etc, Visible and infrared
transparency etc. Dielectric permittivity and refractive index of DLN is lower
than the DLC, whereas optical
transparency is higher than the DLC films.
In this paper deposition, structure, chemical composition
as well as mechanical, optical, electrical, properties of DLN composite film
are elaborated and industrial and prospective applications of DLN films are
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