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 2.
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