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
1 , Ümit Demir 1 and Tuba Öznülüer 1 *
1 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 nanof ilms 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 highresolution
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 mMNa 2 S, 0.3 mM SeO 2 and
EDTA in acetate buffer (pH 4.5) at a potential of -0.02 vs.
Ag|AgCl (3M NaCl).
The bandgap values of the PbSxSe 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 highquality
ternary thin films could be prepared by this UPDbased
electrochemical technique.
PbSexS1-x (200)
ity / Au(111)
s
n
te
In
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] 111,
2670 (2007)
b
a
6th Nanoscience and Nanotechnology Conference, zmir, 2010 289