Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
Synthesis and Characterization of ternary PbS x Se 1-x thin films via Electrochemical Co-deposition
Methods
Fatma Bayrakçeken, Ümit Demir, Tuba Öznülüer*
Department of Chemistry, Arts and Sciences Faculty, Atatürk University, Erzurum 25240, Turkey
Abstract - Thin films of PbS x Se 1-x were electrodeposited on Au (1 1 1) substrates by using a practical electrochemical method, based on
the simultaneous underpotential deposition (UPD) of Pb, S and Se from the same solution containing Pb(CH 3 COO) 2 ,SeO 2 ,Na 2 S and
EDTA at a constant potential. PbS x Se 1-x nanofilms were characterizated by X-ray diffraction (XRD), atomic force microscopy (AFM),
FTIR spectroscopy techniques. AFM, XRD, and FTIR results revelead that ternary lead chalcogenide nanofilms having high crystallinity
were deposited at a kinetically preferred (200) orientation on the Au (111) substrates.
The lead salts (PbS, PbSe and PbTe) and their alloys are
narrow band gap semiconductors which have been studied in
the field of IR detection and thermoelectric devices [1].
More recently, further interest in the different lead-salt alloys
has been created as a result of experiment in high-resolution
spectroscopy and in air pollution measurement using tunable
lead-salt diyote lasers. In addition to infrared detectors and
emitters, narrow gap semiconductors have potential
application in magnetoresistive and Hall effect devices as
well as in thermoelectric devices.
Emphasis is placed on the ternary alloy systems of PbS x Se 1-x ,
Pb 1-x Sn x Se, PbSn 1-x Se and Hg 1-x Cd x Te due to scope for
regulation of their physico-chemical properties through
variation of composition. It is possible to vary such
electrophysical characteristics as type of conductivity
concentration of main current carrier, band gap (E g ) etc.
Individually, both the lead salt compounds PbS and PbSe
have been widely used as radiation dedectors sensitive to
near-infrared wavelengths[2]. Mixed compounds of the form
PbS x Se 1-x, however, offer potentially useful dedectors of
intermediate wavelength, broad band, and perhaps unique
response. Lead chalcogenides films have been prepared by
atomic layer epitaxy (ALE), chemical bath deposition
(CBD), and electrochemical deposition[3]. Demir et al. have
recently reported atom-by-atom electrochemical
codeposition method to prepare PbS[4], ZnS[5] and CdS[6]
thin films on Au(111). In this study, we also have shown that
the highly oriented PbS x Se 1-x thin films have been
successfully prepared by an electrochemical co-deposition
method, which based on the upd or surface-limited reaction
of Pb, Se and S at pH 4.5. The appropriate co-deposition
potentials based on the underpotential deposition (upd)
potentials of Pb, Se and S have been determined by the
cyclic voltammetric studies. The films were grown from an
electrolyte of 2.5 mMPb(CH 3 COO) 2 ,2 mM Na 2 S, 0.3 mM
SeO 2 and EDTA in acetate buffer (pH 4.5) at a potential of
-0.02 V vs. Ag|AgCl (3 M KCl).
The bandgap values of the PbS x Se 1-x films were
determined by absorbance measurement in the wavelength
range 1280-5000 nm using Fourier transform infrared
spectrophotometer. X-ray diffraction patterns were used to
determine the sample quality, crystal structure and lattice
parameter of the films. PbS x Se 1-x thin films were found to be
single crystalline in nature as confirmed by XRD patterns
and have a predominantly rock salt (NaCl) structure
(Figure 1). The morphological investigation of PbS x Se 1-x
films revealed that the film growth follows a 3D nucleation
and growth mechanism. In conclusion, morphology and
structure analyses confirm that high-quality ternary thin
films could be prepared by this UPD-based electrochemical
technique.
Intensity/ a.u.
PbSe xS 1-x (200)
Au(111)
20 25 30 35 40 45 50 55 60
2/deg
Figure 1. XRD patterns of PbSe x S 1-x thin film on Au (111)
electrode after potential controlled deposition at -400 mV, pH 4.5;
(a) 30 minutes and (b) 1 hour.
*Corresponding author: toznuluer@gmail.com
[1]S. Kumar, M. Hussain, P. T. Sharma, M. Husain Journal of
Physics and Chemistry of Solids 64, 367 (2003)
[2]B. A. Riggs J. Electrochem. Soc. 107, 708 (1967).
[3]M. Alanyalioglu., F. Bayrakceken, Ü. Demir, Electrochim. Acta
105, 10588 (2009)
[4]T. Oznuluer, I.Erdogan, I.Sisman and U Demir Chemistry of
Materials 17, 935 (2005)
[5] T. Oznuluer, I.Erdogan, I.Sisman and U Demir Lagmuir 22,
4415 (2006)
[6] İ.Sisman,M.Alanyalioglu and Ü.Demir J.Phys.Chem.C 111,
2670 (2007)
b
a
6th Nanoscience and Nanotechnology Conference, zmir, 2010 269