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