International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 4, Issue 4, April 2015
ISSN 2319 - 4847
Study The Structural and Optical Properties of
Fe2O3 Thin Films Prepared by RF Magnetron
sputtering
Prof. Dr.Abdulhussein K.Elttayef1, Assist. Prof.Dr Muneer H.Jaduaa2 , Muthana A.Muhammed2
1
Ministry of Science and Technology
2
University of Wasit, College of Science
ABSTRACT
Fe2O3 thin films were deposited by reactive R.F. magnetron sputtering method on glass substrates with different thicknesses 50
and 100and 370 nm. The structure of Fe2O3 thin films was tested with the X-Ray diffraction and it was formed to be
amorphous and after annealing becomes single crystal with recognized peak in (003). The surface morphology of the deposits
materials have been studied by using atomic force microscope (AFM). The grain size of the nanoparticles observed in the range
of (66.3), (72.37) and (79.23) nm for the thickness of 50, 100 and 370 nm respectively. The optical properties concerning the
absorption and transmission spectra were studied for the prepared thin films.
Keywords: Fe2O3: Thin Film; Nanostructure; Optical; Sputtering RF.
1. INTRODUCTION
Sputtering simply is a term used to describe the mechanism in which atoms are ejected from the surface by energetic
particles (almost ions A under high voltage acceleration ion). Two approaches can be followed to produce ions and
sputter the target materials. The first is quite straightforward by using an ion source which is aimed toward the target
Collecting the sputtered particles on a substrate enables the deposition of a thin film. However, ion beam sputtering is
not widely used for industrial large scale applications. Ions guns are more often utilized in surface analytical techniques
such as SIMS (secondary ion mass spectrometry) or to bombard the substrate during thin film deposition [1]. The
sputtering process with the assistant of magnetron cathodes is called magnetron sputtering which is widely used in both
scientific and industrial fields [2]. A magnetron uses a magnetic field to confine electrons close to the cathode, making
it easier to sustain an electrical discharge at low pressure. There are various geometries but all magnets are arranged in
such a way that the magnetic field lines are parallel to the cathode surface and perpendicular to the electric fielding
lines. This causes the secondary electrons to drift in a closed path in the – E ×B direction, also known as the Hall
Effect, trapping the electrons near the cathode surface. This arrangement results in enhanced ion bombardment and
sputtering rates for both DC and RF discharges. Magnetron sputtering is particularly useful when high deposition rates
and low substrate temperatures are required [3]. In RF magnetron sputtering, cathode and anode are changeable and for
very short cycles, target functions as anode which cause the removal of insulating layer. By doing so, the process can
continue [4, 5]. Due to the predicted half-metallic nature and high polarization (100%), Fe3O4 thin films have drawn a
great deal of interest as promising candidates for application in tunneling magneto resistance (TMR) devices. Single
crystalline thin films have been epitaxial grown on MgO (100) substrates, due to the good lattice match between the
oxides. [6–8] Polycrystalline Fe3O4 thin films have also been deposited on Si substrates to study the properties. [9, 10]
The deposition methods used to date include plasma assisted molecular-beam epitaxial (MBE) [6] pulsed laser
deposition (PLD) from oxide targets [7, 9] and reactive sputter deposition from an Fe target with Ar–O2
mixture gas flow[8,10] Besides Fe3O4 , other iron oxides, Fe2O3 , FeO, and some nonstoichiometric oxides, have been
reported to be present in the deposited films, depending on the deposition conditions.[11,12] Fe2O3 is brown or reddish
brown and hence can be easily distinguished from the other oxides, FeO and Fe3O4 , which are black. The crystal
structure
of both of the later oxides are based on the fcc Bravias Lattice with lattice parameters a50.8936 nm for Fe3O4 and
0.4307 nm for FeO. It has been reported that Fe3O4 can be obtained in polycrystalline thin films only after a certain
critical thickness has been deposited [13] which is not ideal for practical device applications. Here we report our
investigations of the deposition of Fe2O3 thin films RF sputtered from an iron oxide target.
Volume 4, Issue 4, April 2015
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 4, Issue 4, April 2015
ISSN 2319 - 4847
2. EXPERIMENTAL DETAILS
(Fe2O3) thin films were prepared on glass substrates via reactive radio frequency (RF) magnetron sputtering system using
pure iron oxide (Fe2O3) target with purity of 99.99%. The glass substrates were cleaned chemically and ultrasonically,
the glass substrate was cleaned by ethanol followed by distilled water rinse, subsequently samples are placed in beaker
contain distilled water inside ultrasonic device for 2 hour at 353K The substrates and target were fixed in the chamber of
magnetron sputtering system . The base pressure of the deposition chamber was kept at 6 × 10−5 Torr,
3. Results and discussion:
3.1 Structural Properties
The X-Ray diffraction (XRD) analysis is conducted to determine the Phases and the grain size. The XRD patterns for the
investigated Fe2O3 samples prepared at room temperatures and constant deposition time as well as those deposited at
different thicknesses are shown in Fig.(1 a,b,c).And after annealing at 500oC the XRD pattern are shown in
Fig.(2,a,b,c).
Fig. (1-a, b, c) XRD of Fe2O3 thin films (50,100 and 370 nm) before annealing.
Volume 4, Issue 4, April 2015
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 4, Issue 4, April 2015
ISSN 2319 - 4847
Fig. (2-a, b, c) XRD of Fe2O3 thin films (50,100 and 370 nm) after annealing.
The structure of Fe2O3 thin films were formed to be amorphous and after annealing becomes single crystal with
recognized peak in (003) at 31.2o. These results in agreement with the standard Fe2O3 X-ray diffraction data file [N
1997 JCPDS prevalent].
The mean crystallite size has been obtained with Scherer relation:
D = kλ / (βCosθ)
(1)
where D is the crystallite size, k is a fixed number of 0.9, λ is the X-ray
Wavelength, θ is the Bragg’s angle in degrees, and β is the full-width-at-half maximum (FWHM) of the chosen peak.
The mean size of crystallization calculated for 50,100 nm and 370 nm thin films of Fe2O3 is found to be1.63 nm ,0.87nm
and 1.05 nm respectively.
3.2.Morphology
Morphological information of these thin film surfaces was analyzed by the AFM as shown in fig. (3) and fig. (4). From
the topographic images, it can be seen that the films deposited with thickness of 50 and 100 nm appear to be more
uniform that the topography of the sample deposited with thickness of 370 nm. The grain size of the nanoparticles
observed in the range of (66.3), (72.37) and (79.23) nm for the thickness of 50, 100 and 370 nm respectively.
Volume 4, Issue 4, April 2015
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 4, Issue 4, April 2015
ISSN 2319 - 4847
Fig. (3):AFM images for Fe2O3 thin films before annealing: a) 50nm b) 100nm c) 370 nm.
Fig.4.AFM images for Fe2O3 thin films after annealing: a) 50nm b) 100 nm c) 370 nm.
3.3 Optical Properties
Figure (5) illustrates transmittance spectrum of Fe2O3 films for different thickness (50,100,370 nm.). It is observed that
maximum transmittance of 85% at (50 nm) thickness for wavelength range (600-1100 nm).After annealing the
transmittance decrease to 75% for the same thickness as shown in figure(6)
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 4, Issue 4, April 2015
ISSN 2319 - 4847
Fig. (5) Transmittance spectrum of Fe2O3 films for different thickness before annealing.
Fig. (6) Transmittance spectrum of Fe2O3 thin films after annealing temperature of 500 oC.
3.4 The Energy gap
The energy gap can be calculated from equation:
( α h)1/2 = B ( h  – Egopt. )1/2 (2)
Where :( α )Absorption coefficient, (h) Planck's constant, ( ν) The frequency of the photon , (hν) photon energy, (B )
Constant depends on the probability of the transfer of electronic. The relations are drawn between (α hν)2 and photon
energy ( hν) before and after annealing ,as shown in figures (7.a,b and c) and figure (8,a,b and c) respectively .
a
Eg=3.72eV
Volume 4, Issue 4, April 2015
b
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 4, Issue 4, April 2015
ISSN 2319 - 4847
c
Eg=3.81eV
Fig. (7, a, b, c) allowed direct transition electronic for Fe2O3 thin films before annealing: a) t=50 nm, b) t=100
nm, c) t= 370 nm
Fig. (4-13) allowed direct transition electronic for Fe2O3 thin films after annealing: a) t=50 nm, b) t=100 nm, c) t= 370
nm
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 4, Issue 4, April 2015
Thickness (nm.)
ISSN 2319 - 4847
Allowed photon energy
Eg (eV) before annealing
Allowed photon energy
Eg(eV) after annealing
50
3.68
3.70
100
3.72
3.75
370
3.81
3.85
4.Conclusion
We have successfully prepared Fe2O3 films by reactive R.F. magnetron sputtering method on glass substrates with
different thicknesses. The resulting Fe2O3 films were characterized by XRD measurement and AFM. The optical
properties concerning the absorption and transmission spectra were studied for the prepared thin films.
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Author
AbdulhusseinK.Elttayef, is currently a professor of physics At the Applied physics center,
Baghdad, Iraq. He received his Ph.D Degree from Heriot –Watt University (U.K) in 1990. His
currently research Interests include the preparation of nano films (semiconductors and polymers) by
different methods for applications of gas sensors, solar cells and optical detectors. He has written 40
scientific publications in this area
Muthana A.Muhammed M.SC student in physics department, college of science, Wasit University. His research
interest includes the preparation of nano films and applications .
Muneer H.Jaduaa, He is Assistant Proff. ,at physics dept., college of science, Wasit university. He is leading research group in
the field of solid state and material Science.
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