Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
Electrical, structural and optical properties of spray deposited SnO 2 and SnO 2 :F thin films
Demet Tatar 1* , Güven Turgut 1 , Erdal Sönmez 1 , Bahattin Düzgün 1 , and Mehmet Ertugrul 2
,1 K. K. Education Faculty, Department of Physics, Ataturk University, Erzurum 25240, Turkey
2 Engineering Faculty, Department of Electric-Electronic, Ataturk University, Erzurum 25240, Turkey
Abstract—The undoped and fluorine doped thin films are synthesized by using cost-effective spray pyrolysis technique. The dependence optical
structural and electrical properties of SnO 2 films, on the concentration of fluorine is reported. Optical absorption, X-ray diffraction, scanning
electron microscope (SEM) and Hall effect studies have been performed on SnO 2 :F (FTO) films coated on glass substrates.X-ray diffraction
pattern reveals the presence of cassiterite structure with (200) preferential orientation for FTO films. The roughness of the films changed from
22,52 to 15,52 nm. Atomic force microscopy (AFM) study reveals the surface of FTO to be made of nanocrystalline particles. The electrical
study reveals that the films exhibit n-type electrical conductivity. The 20 wt% F doped film has a minimum resistivity of 1,29.10 -4 Ωcm, carrier
density of 8,48.10 18 cm -3 and mobility of 568 cm 2 V -1 s -1 . The sprayed FTO film having minimum resistance of 12,46 Ω/cm 2 and a good
transparency in the visible, these films are useful as conducting layers in electrochromic and photovoltaic devices and also as the passive counter
electrode.
The undoped stoichiometric SnO 2 films have very high
electrical resistivity because of their low intrinsic carrier
density and mobility [1]. Therefore the challenge is to prepare
non-stoichiometric doped thin films. The conductivity of
weakly nonstoichiometric tin oxide films is supposed to be due
to doubly ionized vacancies serving as donors [2]. Dopants as
antimony, Sb, indium, In, and fluorine, F, are frequently used.
The fluorine-doped tin oxide (FTO), being an n-type, wide
band gap semiconductor (≥3 eV) with special properties, high
transmittance in the visible range and high reflectance in the
infrared, excellent electrical conductivity, greater carrier
mobility and good mechanical stability are used in different
devices like solar cells as transparent, protective electrodes
[3], flat panel collectors as spectral selective windows, sensors
for detection of gases, sodium lamps, gas sensors, and
varistors [4–6]. FTO films have been prepared by various
techniques, such as chemical vapour deposition, metalorganic
deposition, rf sputtering, sol–gel, and spray pyrolysis [7–9].
Spray pyrolysis is used to prepare films because of its
simplicity and commercial viability [10,11]. Moreover, the
spray pyrolysis technique is well suited for the preparation of
doped tin oxide thin films because of it is ease to adding
various doping materials, controlling the texture via various
deposition temperatures and mass production capability for
uniform large area coatings.
The prime aim of this work is to produce low thickness with
high transmission, low resistance and highly conducting F
doped tin oxide thin films with higher figure of merit by costeffective
chemical spray pyrolysis technique and study their
optical, structural, electrical and optoelectrical properties.
and X-ray rocking curve with CuK α radiation. The surface
morphology of the FTO thin films were observed by an atomic
force microscopy (AFM) (by products nanomagnetic-inst).
The electrical studies were carried out by Hall measurements
in van der Pauw configuration. The visible transmission
spectra of FTO films were measured using UV– spectrometer .
(a)
(b)
Figure 2. AFM images of samples, a) SnO 2 (TO), b) SnO 2:F (FTO)
The physical properties of the spray pyrolyzed tin oxide and
FTO thin film deposited at 420˚C from SnCl 2 .2H 2 O precursor
have been presented. The transmittance enhancement of these
films is due to the well-crystallized film and the pinhole free
surface. X-ray diffraction pattern reveals the presence of
cassiterite structure with (200) preferential orientation for
FTO film. The roughness of the films changed from 22,52 to
15,52 nm. The AFM analysis showed that improved
morphological structural of the films. The FTO film deposited
on 420°C revealed the minimum resistivity of about 1,29.10 −4
Ω.cm and high transmittance in the visible band. This high
conductivity and transparency of FTO film suggest that these
films are likely to be useful as electrical contacts in various
electronic and energy harvest applications.
*Corresponding author: demettatar@atauni.edu.tr
Figure 1. X-ray diffraction pattern of samples
Figure 1. shows the X-ray difraction (XRD) patterns of the
FTO films. XRD studies were made with a X-ray diffraction
[1] A.V. Moholkar, et. al. Applied Surface Science 255, 9358–9364 (2009).
[2] Z.M. Jarzebski, J.P. Marton, J. Electrochem. Soc. 123, 2 (2000).
[3] S. Colen, Thin Solid Films 77, 127 (1981).
[4] P.S. Patil, et. al. Thin Solid Films 437, 34 (2003).
[5] A. Dima, et. al. Thin Solid Films 427, 427 (2003).
[6] D.S. Lee, et. al. Thin Solid Films 416, 271 (2002).
[7] J. Kane, H.P. Schweizer, J. Electrochem. Soc. 123, 270 (1976).
[8] T.N. Blanton, M. Lelental, Mater. Res. Bull. 29, 537 (1994).
[9] K.Y. Rajpure, et. al. Mater. Chem. Phys. 64, 184 (2000).
[10] P.S. Patil, Mater Chem Phys. 59, 158 (1999).
[11] E. Elangovan, K. Ramamurthi, J. Optoelect. Adv. Mater. 5, 45 (2003).
6th Nanoscience and Nanotechnology Conference, zmir, 2010 372