International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 9, September 2013
ISSN 2319 - 4847
Synthesis of Aluminum and Boron co-doped
ZnO nanostructure films on Glass Substrate
Anwar Hussein Ali1, Rashid HashimJabbar2,Abdulhussein K. Elttayef 2
1
Dept. of Physics, College of Science, Al-Mustansiriyah University, Baghdad, Iraq.
2
Center of Applied Physics, Ministry of Science and Technology, Baghdad, Iraq.
Abstract
In this study, undoped and Aluminum and Boron co-doped ZnO(AZB)thin films were deposited at 450 oCon glass substrates by
Spray Pyrolysis methodin (150±5 nm). Characterization techniques of XRD, SEM and UV-visible spectra measurements were
performed to investigate the effects of Aluminum and Boron co-doping on the structural and optical properties of ZnO thin
films.The structure of AZB nanostructure films hasbeen found to exhibit the hexagonal wurtzite structure. The increase of AZB
concentration caused to decrease the grain size, bandgapfor AZB(2 at %) and increase the transmittance for AZB(2, 4, 6 at %) in
a visible region .The structural details and microstructurewere obtained from X-ray diffraction and scanning electron
microscope(SEM).
Keywords:ZnOnanostructures, boron and aluminum co-doped, Synthesis.
1. Introduction
Semiconductor ZnO has been the subject of research for many applications for the past several years, because the material
is nontoxic, biosafe, chemically stable, and biocompatible. ZnO has a direct wide bandgapof around 3.2-3.37eV at room
temperature 300K[1,2], where the bottom of the conduction band is formed from the 4s levels of Zn2+ and the top of the
valence band is built from the 2p orbitals of O2-. It has strong ionic bonding and exciton binding energy of 60 meV. low
resistivity and high transparency in the visible range and high light trapping characteristics [3]. [4]ZnO has attracted
increasing attention as a potential material for optoelectronic devices such as low threshold blue/UV lasers, solar cells,
LEDs, sensors, display devices and photodetectors[5-7].The synthesis of nanoparticleshas become a highly developed _eld
owing to thescienti_c and technological interest due to the structuralpeculiarities and unusual physical and chemical
propertiesthey may lead to [4]. In recent years, it has beenfound that ZnO can be synthesized by various routessuch as
electron beam evaporation technique [5], chemicalspray pyrolysis technique [1], RF thermal plasmaevaporation [6],
sol_gel method [3, 7], and precipitation[1, 7] methods. Among these methods, precipitation hasmany advantages over the
other methods, for example,it is unsophisticated and a low cost method[2,4,8].Zinc oxide (ZnO) has been used in a wide
range of products for many years, including, amongothers, varistors, surface acoustic wave devices and cosmetics. Besides
these established applications,ZnO and its ternary alloys are now also being considered as potential materials
foroptoelectronic applications, such as light emitting diodes, photovoltaics, sensors, displays, etc[9].
2. Experimental
Nanostructure films of AZB (0.0, 2, 4, 6, 8 at %) i.e.[ZnO pure, ZnO:(B 1%+Al 1%),ZnO:(B 2%+ Al 2%),ZnO:(B 3%,Al
3%),ZnO:(B 4%,Al 4%)]prepared by spray pyrolysis deposition (SPD) technique in air from zinc nitrate
(Zn(NO3)2.6H2O) diluted with distilled water to concentration of molarities equal 0.075 M, (Zn(NO3)2.6H2O) is a solid
material which has a white color and its molecular weight (297.4 g/mole). The deposition method involves the
decomposition of an aqueous solution of zinc nitrate. The spray solution is sprayed onto heated substrates held at 450oC.
The time of the deposition is 3 sec. each 42 sec., Compressed air is used as a gas carrier and it is fed with the solution into
a spray nozzle at a preadjusted constant atomization pressure. Film thickness(t=150±5 nm) was determined by(TFProbeTM
Spectroscopic Reflectometer film thickness measurement system). Diffraction studies are carried out using X- Ray
Shemadz XRD – Diffractrometer (operated at 40 kV an accelerating potential and 30 mA with filtered CuKα radiation
0.15406 nm wavelengths) was performed to identify the crystalline phases present in the deposited films. The size and
morphology of the AZB nanostructuresamples were observed with a scanning electron microscope (SEM).
3. Result and discussion
3.1. Structural analysis:The XRD graphs of AZB nanostructure films are shown in fig.1. It is obvious the
nanostructurefilm is polycrystalline and all the samples have hexagonal wurtzite structure. the intensity of ZnO pure
nanostructure film is more than the intensity of AZB nanostructure for (002) plane.
Volume 2, Issue 9, September 2013
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 9, September 2013
ISSN 2319 - 4847
Figure 1. X-ray diffraction pattern ofAZB nanostructure with concentration: 0.0 to 8 at.%.
FWHM COS(θ)
The crystallite size and strain dependon the 2θ peak position which enables us to determinethe effect of peak broadening
using the Williamson-Hall(W-H) method:
….. (1)
The plot of 4 sinθ versus β cosθ taking (100), (002), and (101) lattice planes correspondingto the wurtzite phase of ZnO
are shown in Figure 2.From the linear fit to the data, the crystallite size wasextracted from the y-intercept and the
micro strain ε from theslope of the straight line. The strain is due to the incorporationof a dopant in the periodic lattice.
The W-Hplots show a negative strain for AZB nanoparticles which is an indication of latticeShrinkage[10].
0.025
0.024
0.023
0.022
0.021
0.02
0.019
0.018
0.017
0.016
0.015
0.014
0.013
0.012
0.011
0.01
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
0
ZnO pure
AZB 6%
1
1.05
AZB 2%
AZB 8%
1.1
1.15
AZB 4%
1.2
1.25
1.3
4SIN(θ)
Figure 2. W-H plots of AZBnanostructure with concentration: 0.0 to 8 at.%.
The obtained crystallite size (DW-H)and microstrain (ε) calculated by William-Hall method, crystallite size measured by
scanning electron microscope(DSEM (nm)) and energy gap for different samples are summarized in Table 1.
Table 1. W-H crystallite size (DW-H), DSEM, strain (ε) and optical gap (Eo) for AZB
nanostructure with concentration: 0.0 to 8 at.%.
Doping(
D SEM
Eg(eV
ε(x10DW-H (nm)
3
%)
(nm)
)
)
0
60.3
31
9
3.25
2
14.5
20
3.7
3.22
4
9.5
15
5.5
3.30
6
8.0
12
9
3.31
8
7.6
8
3.3
3.25
3.2.Optical properties: The transmittance spectra of AZB nanostructure films in thewavelength range of 300–1100 nm are
shown in Fig. 4(a).where the transmittance at 550 nm is increase with increase the concentration 0.0 to 6 at % then
decrease for the concentration 8 at %.
Volume 2, Issue 9, September 2013
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 9, September 2013
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Figure 3.Transmittance of AZB nanostructure with concentration: 0.0 to 8 at.%.
Optical absorption coefficient ( ) is calculated using Lambert'slaws using following equation [11].
…….. (2)
Where T is the transmittance and is the thickness of film.The optical bandgap of AZB nanostructure films is estimated by
the extrapolation of the linear portion of
vs plots. For the allowed direct transition, the variation of a with photon
energy ( ) obeyTauc’s plot method[11] .
where A is a constant,
is optical bandgap, is plank constantand is the absorption coefficient. The plot of
versus
for AZB nanostructure films at different concentration is shown in Fig. 4(a).A plot of
versus
often
2
yields a reasonably goodstraight line fit to the absorption edge of the glass and theextrapolation
at which
= 0,
provides a convenient experimentalbenchmark for optical bandgap.Figure 3 shows the UV-visible absorption spectra of AZB
nanostructure with concentration: 0.0 to 8 at.%.For the direct-band-gap semiconductorof ZnO, the band gap energy can be
expressed by thefollowing equation [3]:
where α is the absorption coefficient, hνis the photonenergy, is the edge-width parameter and
is the
band-gap energy for direct transitions as indicated inFigure 4.[12].
Fig. 4. (a) Tauc’s plots of AZB nanostructure films at different Al and B with fixed concentration. (b) Absorptance spectra of AZB
nanostructure filmsat different Al and B with fixed concentration. (c) Effect of Al and B concentration on the bandgap of AZB
nanostructure films.
3.3. Surface morphology:The surface morphology of the AZB nanostructures is observed using scanning electron
microscope (SEM).The change in the morphology of AZB nanostructure films is due to the difference in ionic
radiusbetween B3+ (0.041 nm) and Al3+ (0.054 nm) with Zn2+ (0.074 nm)[13].The surface morphology usingscanning electron
Volume 2, Issue 9, September 2013
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 9, September 2013
ISSN 2319 - 4847
microscope (SEM) of the AZB nanostructures is observed to be drastically influenced with variation in Al and B doping concentration as
shown in figure(4).
2%
0.0
6%
4%
8%
Figure.4.SEM image of AZB nanostructure with concentration: 0.0 to 8 at.%.
4. Conclusions
The crystallite size calculated by W-H and by scanning electron microscope is decrease with increase of concentration of
boron and aluminum co-doped ZnO.It wasfound that the increase of concentration of Al and B due to decrease of grain
size. The increase of AZB concentration caused to decrease the bandgap for AZB(2 at %) and increase the transmittance
for AZB(2, 4, 6 at %) andthe absorptance was in the minimum value for AZB( 4, 6 at %) in a visible region .
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Volume 2, Issue 9, September 2013
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 9, September 2013
ISSN 2319 - 4847
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Author
Anwar H. Al-fouadi, Ph.DAl-Mustansiriyah University,College of Science, Dept. of Physics, Msc. Aston university in
Birmingham U.K. 1983, Bsc. Al-Mustansiriyah University, College of Science, Dept. of Physics. Assistant proff. science
Al-Mustansiriyah University in field of solid state material science.
Rashid HashimJabbar, Ph.D student. Presently,M.Sc. in Physics Science degree in 2009,Al-Mustansiriyah
University,College of Science, Dept. of Physics,and BSc. in Department of Physics College of sciencein
1989,from University of Baghdad, a researcher at the Applied Physics Center and member of thin films
application Department, Ministry of Science and Technology, Baghdad, Iraq
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.
Volume 2, Issue 9, September 2013
Page 173