Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
Effect of Ru and Al substitutions on sol-gel derived ZnO thin films.
M. Bektas 1,2, ,M.Erol 1,2 *, O. Sancakoglu 1,2 , M. Faruk Ebeoglugil 1,2 and Erdal Celik 1,2
1 Dokuz Eylul University, Department of Metallurgical and Materials Engineering, 35160 Buca, Izmir- Turkey.
2 Izmir-
Turkey.
Abstract-In this study, ZnO thin films were deposited on glass substrates via sol-gel technique for sensor applications. Transparent solutions
were prepared from Zn, Ru, Al based precursors. The solutions were deposited on glass substrates by using spin coating technique which
provides thin and smooth films. Deposited films were dried at 300 o C for 10 min in order to remove hydrous and volatile content,
subsequently to remove organic content films were heat treated at 500 o C for 5 min and then they were annealed at 600 o C for 1 hour to
obtain ZnO based films in air atmosphere. Finally the surface morphology and roughness of the films were determined via AFM (atomic
force microscopy) and profilometer respectively. The phase structure was determined by XRD.
The importance of zinc oxide (ZnO), among other metal
oxides, is increasing due to many applications. Thin films
of zinc oxide combine interesting properties such as nontoxicity,
good electrical properties, high luminous
transmittance, excellent substrate adherence, hardness,
optical and piezoelectric behaviour and its low price. ZnO
has relatively high physical and chemical stabilit ies, and
hence it has many high temperature applications [1].
Zinc oxide (ZnO) is an important multifunctional
material with applications such as transistors, gas sensors,
solar cells, nanocantilevers, etc [3]. Although efforts are
continuing for CO gas sensing using the hetero structure of
SnO2 and ZnO [2], experimental results on pure ZnO for
CO sensing is lacking and it may be related to rapid grain
growth and densification. For gas sensors, it is necessary
to have a porous microstructure with small particle size
yielding large ratio of the surface area to the bulk [2].
Th in film sensors (the film thickness is typically less
than 1 μm) are of interest because of their relatively small
size and low power consumption. In accordance to the
parameters above, sensing capacity is related to the
microstructure and phase structure of the films. By this
way small additions of substitutional elements to the films
which effects the microstructure and sensing capacity.
For the high conductivity and good optical
transmittance, 1TAl-doped ZnO (AZO) films have drawn
considerable attention for transparent conducting
electrodes. Undoped ZnO usually contains various
intrinsic defects such as Zn vacancies, interstitial Zn, O
vacancies, interstitial O, and antisite O (O Zn ). These
intrinsic defects form either acceptor level or donor level
in the band gap that would greatly affect the luminescent
properties of ZnO . By introducing extrinsic dopant Al, the
defect environment is changed whether the Al atom
substitutes the zinc atom or it occupies the interstitial site
[4]. Undoped ZnO responses perceptibly to LPG while Ru
doped sample highly senses ethanol vapors [5]. Scientific
studies about this topic point out that substitution causes
change in the electrical properties and particle size. Also
substitution is important in selective sensing of gases or
substances.
In this research; pure, Ru and Al substituted ZnO thin
film were deposited on glass substrates. A sol-gel route
was derived to produce thin films. The precursors which
were used to produce sols were listed in Table 1.
Spin coating technique provides nanoscale and smooth
films to be deposited. Thus the films were deposited by
technique mentioned above nano scale pores and nano
scale island like structures can be obtained. The decrease
in the pore size of a sensor from micron scale to nano scale
provides high efficiency and selectivity about gas or
substance sensing.
Table 1. Chemicals used to produce ZnO thin films.
Precursor Amount Precursor Amount
ZnCl2 0,225 g Methanol 8 mL
AlCl3 0,012 g Glacial Acetic Acid 0,5 mL
RuCl 3 0,011 g Triethanolamine(TEA) 0,5 mL
In order to deposit thin films on to the glass substrates
spin coating technique was employed. The coating regime
was represented in Figure 1.
Cycles (rpm)
1000
800
600
400
200
0
0 20 40 60 80 100 120
Time (sec.)
Figure 1. Spin coating regime of solutions
Finally the structure, morphology, electronic properties,
gas sensing capacities will be accompanied by using x-ray
diffractometer (XRD) and energy dispersive spectroscopy
attached scanning electron microscopy (SEM-EDS),
atomic force microscopy (AFM) in details.
The authors are indebted to State Planning Foundation
(DPT) and Dokuz Eylul University for financial support.
*Corresponding author: m.erol@deu.edu.tr
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6th Nanoscience and Nanotechnology Conference, zmir, 2010 282