Physical properties of chemical vapour deposited nanostructured carbon thin films

Article abstract of DOI:10.1016/j.jallcom.2010.11.021

A simple thermal chemical vapour deposition technique is employed for the deposition of carbon films by pyrolysing the natural precursor "turpentine oil" on to the stainless steel (SS) and FTO coated quartz substrates at higher temperatures (700-1100 °C). In this work, we have studied the influence of substrate and deposition temperature on the evolution of structural and morphological properties of nanostructured carbon films. The films were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle measurements, Fourier transform infrared (FTIR) and Raman spectroscopy techniques. XRD study reveals that the films are polycrystalline exhibiting hexagonal and face-centered cubic structures on SS and FTO coated glass substrates respectively. SEM images show the porous and agglomerated surface of the films. Deposited carbon films show the hydrophobic nature. FTIR study displays C-H and O-H stretching vibration modes in the films. Raman analysis shows that, high ID/IG for FTO substrate confirms the dominance of sp³ bonds with diamond phase and less for SS shows graphitization effect with dominant sp² bonds. It reveals the difference in local microstructure of carbon deposits leading to variation in contact angle and hardness, which is ascribed to difference in the packing density of carbon films, as observed also by Raman.

Full text of DOI:10.1016/j.jallcom.2010.11.021

Journal of Alloys and Compounds 509 (2011) 1418–1423
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Physical properties of chemical vapour deposited nanostructured carbon
thin films
D.B. Mahadik, S.S. Shinde, C.H. Bhosale, K.Y. Rajpure∗
Electrochemical Materials Laboratory, Department of Physics, Shivaji University, Kolhapur, Maharashtra 416004, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A simple thermal chemical vapour deposition technique is employed for the deposition of carbon films by
pyrolysing the natural precursor “turpentine oil” on to the stainless steel (SS) and FTO coated quartz sub-
strates at higher temperatures (700–1100 ◦C). In this work, we have studied the influence of substrate and
deposition temperature on the evolution of structural and morphological properties of nanostructured
carbon films. The films were characterized by using X-ray diffraction (XRD), scanning electron microscopy
(SEM), contact angle measurements, Fourier transform infrared (FTIR) and Raman spectroscopy tech-
niques. XRD study reveals that the films are polycrystalline exhibiting hexagonal and face-centered cubic
structures on SS and FTO coated glass substrates respectively. SEM images show the porous and agglom-
erated surface of the films. Deposited carbon films show the hydrophobic nature. FTIR study displays C–H
and O–H stretching vibration modes in the films. Raman analysis shows that, high ID/IG for FTO substrate
confirms the dominance of sp3 bonds with diamond phase and less for SS shows graphitization effect
with dominant sp2 bonds. It reveals the difference in local microstructure of carbon deposits leading to
variation in contact angle and hardness, which is ascribed to difference in the packing density of carbon
films, as observed also by Raman.
Received 17 September 2010
Received in revised form 31 October 2010
Accepted 2 November 2010
Available online 10 November 2010
Keywords:
Carbon films
Chemical vapour deposition
XRD
SEM
Contact angle
FTIR
Raman
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
[12], nano-biotechnology [13], etc. Such versatility of this element
in nature results from the unique property of a carbon atom to
Carbon is one of the most abundant elements in the uni-
verse and the most versatile material existing amorphous, glassy
and crystalline forms. This element is the basis of life on Earth
and constitutes interiors of the celestial objects: outer planets,
Uranus, Neptune, and white dwarf stars. Carbon is often consid-
ered to be silicon of the future because of the unique properties
resulting from the variety of possible structural forms. Owing to
their unique atomic structure, outstanding mechanical strength,
thermal conductivity and versatile electronic properties, carbon
nanotubes (CNTs) are key components of a wide range of scientific
and technological studies. In recent years, many efforts have led
to the development of versatile chemical modification methodolo-
gies, targeting CNT derivatives with even more attractive features.
A wide range of electronic properties of carbon from insulat-
ing/semiconducting diamond to metal-like graphite, nanotubes,
and graphene sheets yields many novel technological applications
such as electron field emitters for optical displays [1,2], micro-
fabricated X-ray sources [3], electrode material for fuel cells [4,5],
Lithium ion batteries [6], support for catalyst [7–9], tips for scan-
ning probe microscopy [10], electrochemical actuators [11], sensors
form bonds of many different configurations, called hybridizations:
liner sp1, planar sp2, tetrahedral sp3, etc. All of these cause great
scientific interest in thermodynamic properties of carbon. In addi-
tion to initially developed laser furnace [14] and arc discharge [15]
techniques, catalytic chemical vapour deposition (CCVD) method
[16,17] has been contrived for large scale production of carbon
nanotubes, with various carbon source molecules tested such as
carbon monoxide, methane, benzene, xylene, toluene, etc. These
carbon sources are related to fossil fuels which may not be suffi-
cient in near future; so researchers switched over to reproducible
natural carbon source like camphor and grown various kinds of
nano-carbons [18,19]. This gives new idea to develop nanotechnol-
ogy with eco-friendly and environmentally clean carbon source:
turpentine oil, which is derived from the oleoresin of Pinus species
particularly from Pinus palustris of Pinaceae family. Our effort is
mainly focused on identifying and using regenerative, reproducible
source. A simple template synthesis method has been explored
[20,21] for preparing micro and nanostructured materials. In the
present paper, nanostructured carbon films are grown using a
natural precursor “turpentine oil (C10H16)” as a carbon source in
the simple thermal chemical vapour deposition method, unlike
PECVD, MPCVD, PLD, etc., that are commonly used for the depo-
sition of various types of carbon films. It is worth noting that for
deposition on complex geometrical structures and large sized sub-
∗
Corresponding author. Tel.: +91 231 2609435; fax: +91 231 2691533.
E-mail address: rajpure@yahoo.com (K.Y. Rajpure).
0925-8388/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2010.11.021

D.B. Mahadik et al. / Journal of Alloys and Compounds 509 (2011) 1418–1423
1419
with polarization incident light using a MultiRam (Brucker Made, Germany) spec-
trometer. The films were excited with 1064 nm line of Nd:YAG laser. The scattered
light from the sample was passed through a broadband polarization scrambler
to eliminate polarization effects in the monochromator. The scattered light was
analyzed by means of a MultiRam spectrometer equipped with a LN2-cooled Ger-
manium (Ge) detector with quartz filter.
3. Results and discussion
3.1. X-ray diffraction
Fig. 2(a and b) shows the XRD patterns of carbon thin films
grown on two kinds of substrates (a) stainless steel, (b) FTO
coated quartz glass substrate at typical temperature 1000 ◦C. These
patterns are analyzed by using JCPDS cards no. 00-002-0456
(hexagonal) and 85-1799 (cubic: face-centered) respectively for
SS and FTO substrates. The films are polycrystalline and fit well
with the hexagonal (space group P63mc) and cubic: face-centered
(space group Fm3m (2 2 5)) crystal structures for stainless steel
and FTO coated substrates respectively. Films grown on SS and
FTO show the formation of graphite and C60 carbon form respec-
tively. The characteristic peaks appearing at 2ꢁ = 26.39◦, 44.60◦, and
74.29◦ displays the presence of graphitic carbon nanofibers [22] on
SS substrate and peaks appeared at 30.89◦, 32.51◦, 46.30◦, 48.30◦,
and 54.60◦ show the presence of C60 carbon nanostructure. Car-
bon film deposited on SS substrate shows the stronger (0 0 2) and
(1 0 1) reflections and existence of some weak reflections viz. (1 0 2),
(1 0 4) and (2 0 0). X-ray diffraction of carbon film deposited on
FTO substrate illustrates stronger (5 1 1) and (8 2 2) reflections and
some weak reflections such as (4 2 2), (5 3 1), (4 4 2), (6 2 0), (6 4 0),
(6 4 2), (8 6 2), (10 2 2), (8 6 4), (11 3 3), (12 2 2) and (10 8 2). The rea-
son for relatively lower peak intensities is the lower film thickness
(∼340 nm) and scattering losses. The main driving force for the for-
mation of graphite and C60 carbon is the thermal energy to activate
the large interdiffusion between carbon and substrates.
Fig. 1. Schematic diagram of the chemical vapour deposition system used in the
present experiments.
strate, thermal CVD is an ideal choice. In the preparation of carbon
films, high percentage of sp3 bonded carbon atoms is preferred
in crystal lattice. The influence of substrate surface topography
(viz. stainless steel, fluorine doped tin oxide coated quartz) and
temperature on the evolution of carbon allotropes surfaces topog-
raphy/microstructural and structural properties are investigated
and discussed. The ratio of intensities of D and G bands (ID/IG) of
nanostructured carbon films is studied using Raman spectroscopy.
2. Experimental
The carbon films were deposited on to the stainless steel (SS) and fluorine doped
tin oxide (FTO) coated quartz glass substrates using thermal chemical vapour depo-
sition (CVD) technique. The deposition unit contains a 1.5 meter long quartz tube
(diameter 25 mm) serves as a thermal CVD reactor kept horizontally inside two
horizontal furnaces along the axis of both of them. Schematic diagram of the exper-
imental set-up is shown in Fig. 1. The vapourizing furnace was used to vapourize
turpentine oil (C10H16) and pyrolysing furnace was used to pyrolyse the vapours
of turpentine oil. In the quartz tube, stainless steel and FTO substrates (over which
turpentine oil is to be pyrolysed and deposited) were placed in furnace. Prior to
deposition, the whole deposition chamber was purged with nitrogen for 30 min.
Then temperature of the pyrolysing furnace was elevated from room temperature
to desired deposition temperature under nitrogen atmosphere. Once, the substrates
reached for desired temperature, turpentine oil (2 cm3) kept in quartz boat was
vapourized at 250 ◦C and the vapourized gas was allowed to pass inside the quartz
tube. The depositions were carried out in separate sets of experiments, for substrate
temperatures as 800, 900, 1000 and 1100 ◦C for 30 min. Nitrogen gas was flushed
until the furnaces were cooled down to room temperature.
3.2. Surface morphological study
Fig. 3(a–e) shows the SEM images of carbon thin films grown
on to different substrates at 900 and 1000 ◦C vapourizing furnace
temperatures. The carbon films deposited on rough surfaces, at first,
the atoms are accumulated in the holes that are existent on the sur-
face substrate, but they cannot fill all the holes on the surface, in
this situation the roughness is larger for smaller deposition time.
As the time progresses, the atoms fill the holes and accumulate
in surface and the roughness decreases. This effect promotes the
reduction of surface energy and is related to the film growth rate.
A smaller surface energy on the substrate is related to smoothing
effect in the film deposition, and in this condition, the roughness
The structural characterization of deposited films was carried out, by analyz-
˚
ing the X-ray diffraction patterns obtained using CuK␣ (ꢀ = 1.5406 A) radiation from
a Philips X-ray diffractometer model PW-3710 within the span of angle 10–100◦.
The surface morphology was studied by using JEOL JSM-6360 scanning electron
microscope (SEM), Japan. The wettability of the films was characterized by the
measurement of static contact angle against water in air by contact angle meter
(rame-hart Instrument Co., USA) at room temperature. The diameter of water
droplet used for the measurements was 2.4 mm. Contact angles were measured
at four different points for each sample, and the average value was adopted as the
contact angle. FTIR spectra were recorded on a PerkinElmer spectrum–1 spectropho-
tometer. Raman-scattering experiments were performed in air at room temperature
120
b
300
a
100
250
200
150
100
80
60
40
20
0
10
20
30
40
50
60
70
80
90 100
10
20
30
40
50
60
70
80
90 100
2θ (deg)
2θ (deg)
Fig. 2. XRD patterns of carbon thin films deposited onto the (a) SS and (b) FTO coated quartz glass substrates at 1000 ◦C.

1420
D.B. Mahadik et al. / Journal of Alloys and Compounds 509 (2011) 1418–1423
Fig. 3. SEM images of carbon thin films deposited on SS: (a) 900 ◦C, (b) 1000 ◦C and (c) 1000 ◦C (magnification 20,000×); FTO coated quartz glass substrate (d) 900 ◦C and (e)
1000 ◦C.
is smaller, because the atoms have more easiness to form the car-
bon films. If the surface energy is high, the roughness increases,
because the atoms need high energy to league and to form the film.
In this situation, the final roughness of the carbon films is strongly
related to the surface energy [23]. The films deposited at 900 ◦C on
SS substrate shows the existence of randomly dispersed but homo-
geneous agglomerates which appear to be loose felt. The deposited
films are porous, scraggy but not fragile including voids. Further
observation of the agglomerate surface shows that few nanofibers
are physically entangled and loosely associated into agglomerates
for 1000 ◦C as seen in Fig. 3(b and c). The nanofibers are not coiled
but generally curved with an average outer diameter of 80–100 nm.
The lengths of the nanofibers are difficult to determine definitely
due to the entangled arrangement, but are at least of the order
of microns. Agglomeration of grains is increased with increase in
grain size at higher temperature. Fig. 3(d and e) shows the SEM pic-
tures of the carbon films deposited on FTO glass substrate at 900
and 1000 ◦C. It clearly shows the dense and homogeneous network
of beads and non-aligned CNTs. Highly dense, twisted and homo-
geneous nanobeads having average diameter of about 600 nm are
observed at 900 ◦C. As we increase the temperature up to 1000 ◦C,
the transformation of nanobeads into nanofibers is observed. From
the images, it is seen that the uniformly distributed nanofibers are
grown on the FTO glass than SS substrates. This could be related to
the lattice structure and defects on the substrate surface respon-
sible for the chemical adsorption and subsequent nucleation and
growth [24]. The bare glass substrate which belongs to the amor-
phous structure has smoother surface and less defects than the SS
substrates. It illustrates that the lattice mismatch and defects on the
surface affect the morphology as well as crystal orientation of resul-
tant films. In these samples, the final film structure and morphology
strongly depends on substrate surface conditions.
3.3. Contact angle measurement
Wettability of the film surface is evaluated by measuring static
contact angles for water. The change in water contact angle val-
ues as a function of surface topography is shown in Fig. 4(a and b).
All films show the hydrophobic behaviour. The contact angles of
water droplets on the stainless steel and FTO coated surfaces are
134◦ and 114◦ respectively. The wettability of the film surface is
mainly influenced by the surface chemical composition and mor-
phology. The compact microstructure of the film surface shows
higher water contact angle values as compared to smooth one.
The reason for this behaviour may be that for high roughness gas
bubbles are embedded between the water drop and the insulator
surface [25]. The decrease of the contact angle relates to an increase
in the hydrophilic nature due to the presence of oxidized films. This

D.B. Mahadik et al. / Journal of Alloys and Compounds 509 (2011) 1418–1423
1421
Fig. 4. Contact angle images of carbon films grown at 1000 ◦C on (a) SS and (b) FTO coated quartz glass substrates.
result is relevant to current interest in the application of carbon
3.5. Raman analysis
coatings as bioactive surfaces, for example, in tissue engineering
scaffolds.
Raman spectroscopy is a fast and non-destructive tool for
the effective analysis of bonding behaviour, domain size, inter-
nal stress, etc., in carbon thin films [27]. The Raman peak shapes,
positions, shifts, half-width and intensity gives the comprehensive
information about the chemistry and structure of carbon films.
Inelastic, incoherent stokes Raman scattering of light from the
lattice of diamond was first observed by Ramaswamy [28] and
investigated in detail by Solin and Ramdas [29]. The 1st order zone
center sharp Raman peak of diamond and graphite is observed at
1333 and 1580 cm−1 respectively. All other types of carbon show
broad peaks between 1100 and 1600 cm−1 [30]. Fig. 6(a and b)
shows typical Raman spectra of carbon films grown at 1000 ◦C tem-
perature onto the SS and FTO conducting quartz glass substrate
respectively recorded in the region of 800–1800 cm−1. The central
peak of the crystalline C–C bonding in the longitudinal optical mode
(LO mode) appears around 950–990 cm−1 is superimposed to the
asymmetrical band [31], as observed in both the films. Two first
order broad bands observed at ∼1312, 1278 and 1542, 1534 cm−1
are named D-band (disorder/defect band) and G-band (graphitic
band or E2g2 mode), for SS and FTO glass substrate respectively.
Interestingly, in most cases the intensity of the D-band is higher
than the G-band in glassy carbon [32]. The prominent broad peak
that observed in the grain boundaries at 1542–1544 cm−1 can be
attributed to sp2-bonded carbon and the disordered allowed zone
edge mode of graphite [33]. A careful observation of the intensi-
ties of G and D peaks in both cases indicates that CNTs deposited
on SS substrate are expected to have a better graphitization com-
pared to those deposited on FTO conducting glass substrate may
be due to disorderliness in the film. The disorderliness in the car-
bon films originated from crystalline disordered graphite due to
intermingling of s-(sp3-like) domains in the clusters of p-(sp2-like)
graphite. For these samples, when the surface topography changes,
3.4. Infrared studies
FTIR spectra of carbon films deposited on to SS and FTO sub-
strates are shown in Fig. 5(a and b) in order to decide the vibration
modes for this material. The films show major peaks of O–H and
C–H stretching, C–H–C bending and C C. Films grown on SS sub-
strate (Fig. 5(a)) show the strong IR peak of C–H bending vibration
at 1020 and 1103 cm−1 due to the symmetric and antisymmetric
stretching vibrations. The IR peaks at 3386 and 1621 cm−1 is asso-
ciated with the adsorption of H2O molecules and graphitic nature
(C C) of the carbon. The observed peak at 3386 cm−1 is correspond-
ing to the stretching vibrations of O–H groups. The C–H stretching
vibration peaks are observed at 2858 and 2930 cm−1 correspond-
ing to sp3 and sp2 carbon atoms respectively. These are in good
agreement with those reported by others [26], where the absorp-
tion for C–H stretching vibrations is found in the 2920–3060 cm−1
range on sp2 bonded carbons and in the 2850–2920 cm−1 range
on sp3 bonded carbons. Additionally the H–C–H bending vibra-
tion is observed at 1460 cm−1. Fig. 5(b) shows the FTIR spectra of
carbon film deposited on FTO coated substrate, which reveals the
stretching and bending vibrations of C–H groups, which are per-
tained to the residual FTO surface, with strong peaks appearing
at 2951, 2917, 2850 and 1098 cm−1. Further, the FTO cations are
almost decomposed and eliminated after the thermal CVD process
which is consistent with the intercalation and adsorption into the
layers. The observed peaks of 3400 and 3500 cm−1 are correspond-
ing to the stretching vibrations of O–H groups. The C C and H–C–H
vibrations are also observed at 1617 and 1098 cm−1. In addition to
that, Si–O bending vibration is seen at 512 cm−1 due to quartz glass.
26
a
b
4.0
25
24
23
22
3.8
C=C
Si-O
Bending
3.6
C-H-C Bending
21
3.4
3.2
3.0
C-H Bending
H-C-H Bending
20
C-H Streching
19
C-H Streching
C-H Bending
O-H Streching
3500 3000
18
O-H Streching
C=C
3500
3000
2500
2000
1500
1000
500
2500
2000
1500
1000
500
-1
-1
Wavenumber (cm
)
Wavenumber (cm
)
Fig. 5. FTIR spectra of carbon thin films deposited at 1000 ◦C onto the (a) SS and (b) FTO coated quartz glass substrates.

1422
D.B. Mahadik et al. / Journal of Alloys and Compounds 509 (2011) 1418–1423
D-Band
b
a
G-Band
C-C sp
D-Band
G-Band
800
1000
1200
1400
-1
1600
1800
900
1050 1200 1350 1500 1650 1800
-1
Raman shift (cm
)
Raman shift (cm
)
Fig. 6. Raman spectrum of carbon thin films deposited at 1000 ◦C onto the (a) SS and (b) FTO coated quartz glass substrates.
the change in the ID/IG occurs. The ID/IG is related to the increase
in sp3 bonds in the films. This effect can be confirmed with the
presence of a small peak around 950–1000 cm−1, this is related to
the formation of sp3 bonds due the presence of C–C sp3 bonds. We
observed that the D band appeared at 1312 and 1278 cm−1 for SS
and FTO substrates respectively. The intensity for all bands in the
Raman spectra depends on surface topography. The sp3 bonds are
strong in the FTO than SS surface. These effects are related to the
second order bands due to the presence of nanostructures in the
films and surface energy generated by the different surface topog-
raphy used. The surface energy of SS is high, due to the presence of
the privileged points of deposition and this promotes the sp2 bonds
formation revealed from contact angle measurements. We noticed
that decrease in ID/IG means increase of sp2 bonds in the films, are
promoted by the presence of graphitic form in the film consistent
with the X-ray results. One of the characteristics of the graphite
grains is the formation of bidimensional structures that privileged
sp2 bonds. The presence of second-order bands can influence these
results, because these bands are related to different nanostructures
formed during the growth of films, which are related to the surface
topography.
4. Conclusions
Influence of substrate on the structure and morphology of
nanostructured carbon films by using thermal CVD have been
investigated. XRD shows these films are crystalline with hexagonal
and cubic: face-centered crystal structure for SS and FTO sub-
strate respectively. Uniformly distributed carbon nanofibers have
been detected for films on FTO glass. The contact angles of water
droplets on the stainless steel and FTO coated surfaces are 134◦ and
114◦ respectively, which confirm the hydrophobic behaviour. FTIR
reveals the C–H and O–H stretching vibrating modes corresponding
to sp3 and sp2 carbon atoms. The presence of second-order bands
in Raman spectra shows the formation of nanostructured growth
of films.
Acknowledgement
One of the authors (S.S. Shinde) is highly grateful to the DRDO,
New Delhi for the Senior Research Fellowship through its project
ERIP/ER/0503504/M/01/007.
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