World Journal of Nano Science and Engineering, 2012, 2, 213-218 Published Online December 2012 (
Microstructural Characterization of Large Area C60 Films
Obtained by Conventional Microwave Oven Irradiation
Jacobo Martínez-Reyes1, Lucia Graciela Díaz Barriga-Arceo2, Luis Rendón-Vazquez3,
Reynaldo Martínez-Guerrero4, Néstor Romero-Partida4, Eduardo Palacios-González5,
Vicente Garibay-Febles5, Jaime Ortiz-López1
1National Polytechnic Institute (IPN), ESFM, UPALM, Mexico City, Mexico
2National Polytechnic Institute (IPN), ESIQIE, UPALM, Mexico City, Mexico
3Facultad de Ciencias, UNAM, Mexico City, Mexico
4ROMFER S.A. de C.V., Mexico City, Mexico
5IMP-Molecular Engineering Program, Mexico City, Mexico
Received August 14, 2012; revised August 28, 2012; accepted September 5, 2012
In the present work the synthesis of C60 produced in a conventional microwave oven from the decomposition of cam-
phor resin is reported. The polycrystalline structure of the sample was determined by X-Ray Diffraction (XRD), the sam-
ple showed several phases, the main phase corresponds to fullerene C60 ordered in a Face-Centered Cubic structure (FCC),
with two more structures: one orthorhombic system and the other the monoclinic system coexisting also with graphite
2H phase. It was observed in a Scanning Electron Microscopy (SEM), that the sample formed thin films of stacked
carbon. Whereas in a High Resolution Transmission Electron Microscopy (HRTEM), measurements in Bright Field
mode revealed that the main phase of the material is C60 ordered in FCC structure and the elemental composition and
atomic bonding state can be determined by analyzing the energy with the electron microscope by Elesctron Energy-
Loss Spectroscopy (EELS), technique allowed confirm all the phase C60 established with XRD observations.
Keywords: Microwave-Assisted Synthesis; Carbon Film; Fullerene
1. Introduction
Carbon thin films are important for the development of
applications due to the physicochemical properties [1-5].
Several methods are currently used for the preparation of
carbon films such as: the condensation of steam to car-
bon, magnetron sputtering, mechanical peeling, chemical
vapor deposition, physical vapor deposition [6-11] among
others. In these methods the films are obtained in tem-
perature conditions at ranges of 950˚C - 1250˚C with
different energies from 100 to 1000 eV at pressure from
1 to 5 × 10–7 Tor using inert atmospheres or carbon gases
as control atmospheres, flowing in a continuous way to
obtain small area films with thicknesses from 500 nm to
10 microns and crystalline or amorphous structure [12],
making this synthesis expensive. Comparing the chemi-
cal precursors used in the synthesis of carbon films, it
was observed that organic resins present more advan-
tages than the inorganic precursors because some of
these resins are environment friendly that is why cam-
phor resin was chosen [13-15]. It is important to mention
that camphor C10H16O resin has been successfully used in
carbon nanomaterial synthesis and also in carbon films
[16-20]. Therefore the Microwave Assisted Synthesis
(MAOS) [21-28], is a cost-effective alternative technol-
ogy which reduces the impact on the environment by
saving energy, being able to produce materials and mi-
crostructures that cannot be performed by other methods.
The aim of this work was to find the synthesis and mi-
crostructural of carbon films to characterization them
carbon films by microwave radiation a resins of com-
mercial camphor.
2. Experimental Details
2.1. Microwave Oven Preparation
The plate was removed from the microwave oven and the
samples were placed in a position where the microwave
radiation reaches the maximum. Determinations of max-
imum and minimum points were done as reported in lit-
erature [29]. Resin sample were located in one of the
points where microwave radiation has one maximum.
2.2. Sample Preparation
For this work 250 mg of camphor Sigma-Aldrich were
opyright © 2012 SciRes. WJNSE
placed in a Florence flask because it was observed that
this glass result better than Pyrex glass under the same
radiation condition (Figure 1(a)). The flask volume was
250 ml; the glass container with camphor was located
inside a commercial SANYO microwave oven with a
frequency of 2450 MHz. The sample was heat treated to
the maximum power (1480 Watts) for 5 minutes. Until a
carbon film was observed through the microwave oven
windows. During the heat treatment, the temperature was
measured by using an Infrared Thermometer Cole Palmer
Mod.800-323-4340 with LCD display, with a tempera-
ture range of 18˚C to 900˚C (Figure 1(b)).
2.3. Sample Characterization
The film sample were characterized by X-Ray Diffrac-
tion in a Siemens D-500 diffractometer using CuKα (λ =
1.54 Å).The sample were observed with two instruments
a Scanning Electron Microscope SEM/FIB NOVA 200
(with point resolution of 1.7 Å) and High Resolution
Transmission Electron Microscopy FEI Tecnai G-20 to
200 kV with resolution of 1.9 Å. Also the sample was
analyzed by electron energy loss spectroscopy (EELS)
for quantitative chemical determination and detail about
the e-type vibrations resolution @ 20 to 200 kV. The
micrographs were analyzed using Digital Micrograph
Software version 3.7 for GMS 1.2 Gatan Company.
3. Results and Discussion
3.1. Sample Obtained
The temperature of the substrate and the structure of the
deposited species are the major factors for growth of the
carbon thin film which depend on the wavelength of the
microwaves and the reaction volume, these factors con-
trol the atomic mobility on the surface and determining
the physical characteristics of the deposited films such as:
microstructure, composition and structure. This is be-
cause carbon atoms when exposed to microwave radia-
tion, the temperature can increase rapidly by dielectric
heating [30,31], the mechanism responsible for the po-
larization or the effect Maxwell-Wagner due to the free
electrons in the carbon. It is known that different allo-
tropes or organic precursor upon heating to different de-
grees in a microwave field depend on its structure and
composition for this reason are considered microwave
(a) (b) (c)
Figure 1. (a) Terpenoid C10H16O; (b) Synthesis in micro-
wave oven; (c) Carbon thin films.
absorbing material [32,33]. The average film surface is in
the range from 2 to 12 cm2 (Figure 1(c)), obtaining films
of high surface area compared with the literature that a
macroscopic level the average size of the area of the
films is reported 2 cm × 2 cm [34].
3.2. X-Ray Diffraction Patterns
The diffraction pattern of carbon thin film is shown in
Figure 2. In this pattern many phases were observed and
they were identified using a reference database cards
ICDD PDF-2 Release 2003 [35-39].
It was observed that the well-defined peaks in this
pattern correspond to the highly ordered crystalline struc-
tures. In this pattern those peaks are thin and correspond
to main phase of the sample which is C60 fullerene mo-
lecule ordered in a face-centered cubic structure which is
the phase of higher symmetry. In this pattern a broad
peak, in the range between 15 and 26 degrees can be ob-
served, this peak is crowned by other well defined low
intensity peaks, corresponding to lower symmetry phases
C60 ordered in orthorhombic and monoclinic structures.
Another phase observed was the hexagonal 2H graphite
phase. It can be noticed that the presence of these phases
may be caused by the difference in temperature in the
container and between the sample and glass substrate. A
summary of the observed phases is shown in Table 1.
3.3. Scanning Electron Microscope and Electron
Dispersive Spectroscopy
In Figure 3(a) the scanning electron micrograph of car-
bon film is shown. Since graphite tape may cause confu-
sion with the carbon film, which is commonly used to
hold samples, the carbon film was supported on a copper
In Figure 3(b) it was observed that carbon film con-
sists of a series of stacked monolayers. The film thick-
ness was measured using FEI Nova Nanolab analysis and
imaging software. The film thickness varies from 140.8
to 523.3 nm. A qualitative chemical composition was
Figure 2. XRD pattern carbon thin film.
Copyright © 2012 SciRes. WJNSE
Copyright © 2012 SciRes. WJNSE
Table 1. Phases of the diffraction pattern of carbon film. performed (Figure 3(c)) by Electron Dispersive Spec-
troscopy (EDS). The sample is mainly composed by
carbon (93.88% at) and oxygen (6.12% at).
Name Charter
Parameter (Å)
of Phase (%)
C60a 81-2220
cubic a = 14.16 Fm 3m 82.7
C60b 49-1718 Orthorhombic
a = 9.56
b = 8.87
c = 8.34
- 4.1
C60b 49-1719 Monoclinic
a = 10.27
b = 7.80
c = 9.49
= 92.4
- 2.5
2Hc 89-7213 Hexagonal a = 2.464
c = 6.711
C 4.1
C70d 50-1363 Rhombohedral
a = 9.92
c = 26.51 R3m 6.6
3.4. High-Resolution Transmission Electron
Microscopy-Electron Energy Loss
In Figure 4(a), bright field electron transmission micro-
graph of sample is observed. From this Figure, it is easy
to observe the crystalline behavior of cubic phase C60
(Figure 4(b)). Two interplanar distances were measured,
using the Digital Micrograph program (D.M).
The direction index associated with those d spacing
were [4 0 0] y [3 11] and zone axis from plane (0 4 4).
aReference [37,40], bReference [35], cReference [38], dReference [36].
(a) (b) (c)
EDAXZAF Quantification(Standardess)
Element Normalized
SEC Table: Default
ElemWt%At% K-Ratio Z A F
CK92.0193.88 0.8287 1.0014 0.89941.0001
OK7.996.12 0.0117 0.9840 0.14901.0000
1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00
Figure 3. (a) SEM micrographs of the carbon film; (b) Thickness of carbon film; (c) EDS-carbon film.
Figure 4. (a) Bright field electron HRTEM carbon films; (b) Fast Fourier transformation; (c) EELS spectra. The spectra
show the * and
* peaks in the carbon K-edge; (d) Histogram of the measuring the diameter of the molecule C60.
The buckyball molecule diameter was also measured
using the D.M, It was found that molecule diameter value
was 6.83Å and corresponds to C60 molecule diameter
(Figure 4(d)). The measurement error was 3.95% [40-
The possible existence of small fullerenes is strength-
ened by the observation that the peak of the diameter
distribution shifts from 5 to 7 Å and back again with
increasing residence time, indicating that the smaller
structures is not an artifact of the measurement method.
On the other hand, by the technique of the energy loss
spectrum of electrons in the thin film of carbon corre-
sponds to C60 in the range of 280 to 295 eV (Figure 4(c)).
The peak near 285 eV corresponds to the transition 1S
*(C-C), while the peak 290 eV corresponds to the
transition 1S
* (C-H), these transitions are due to the
formation of covalent bonds with nearby neighbors po-
lymerized C60 cluster [43-46], the hump at 296 eV in the
region of the carbon K-edge this is characteristic of the
C60 molecule and was also identified a peak at 530 eV
corresponding to oxygen. The 285 eV peak is indicative
of the sp2 bonding fraction; the second peak at 287 eV is
attributed to molecular structure within the sample; the
third at 293 eV is determined by sp3 bonding contribu-
tions in the simple.
4. Conclusions
In this work, it was possible to obtain from the pyrolysis
of camphor in a conventional microwave oven, a carbon
thin film.
The film is polycrystalline and consists of fullerenes
arranged in different crystal structures and graphite 2H.
This indicates that the sample is formed within the
furnace in a gradient of temperatures around 800˚C
working with maximum power of the oven. The main
phase corresponds to fullerene ordered in a face-centered
cubic structure. The sample shows oxidation.
The area of the sample is higher than obtained by other
techniques and is a function of the precursor container
volume ratio 10:1.
The surface of the film consists of several monolayer
of carbon molecules stacked carbon, even leading ma-
terial of varying thickness.
It was identified peak near 285 eV corresponds to the
transition 1S * (C-C), while the peak 290 eV corre-
sponds to the transition 1S
* (C-H), these transitions
are due to the formation of covalent bonds with clusters
near neighbords polymerized C60 and a peak at 530 eV
assigned to oxygen.
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