Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
Study on Absorbance of CdS Thin Films from CBD
M. Celalettin Baykul 1 *and Baris Altiokka 2
1
2 Bilecik Vocational School, Bilecik University, Bilecik 11210 Turkey
Abstract-Cadmium sulfide (CdS) thin films have been grown on a glass substrate from aqueous solution by the chemical bath deposition (CBD).
The films are produced at 80±1°C. The band gaps of CdS thin films were found to be between 2,39 and 2,51 eV. The structural
properties and surface morphology of CdS thin films have been studied X-ray diffractometer and Scanning Electron Microscope
(SEM).
CdS is a promising material because of their applications in
optoelectronics, photo catalysts, solar energy conversion, X-
ray detectors, nonlinear optical material and as a window
material for hetero-junction solar cells because it has usually a
high absorption coefficient [1]. The good quality of a thin film
solar cell (CdS/CdTe) strongly depends on the crystalline
quality and compactness of the CdS layers [2]. Although
chemical bath deposition has been used as a technique for
preparing films since 1910, utilization of CBD semiconductors
in photovoltaic devices is much more recent. It started in 1990
with the integration of CdS buffer layers in combination with
sputtered zinc oxide, ZnO, films and led to a new generation
of high efficiency solar cells [3].
In this work, CdS thin films were deposited by CBD on
glass substrates. The substrates are placed in the bath for
different deposition time varying from 10 to 50 min. The
chemical baths were consisting of aqueous solutions with total
volume of 55mL of CdCl 2 (0,004-0,02M), KOH (0,1-0,5M),
NH 4 NO 3 (0,3-1,5M) and CS(NH 2 ) 2 (0,04-0,2M). CdS thin
films have been also produced on the same glass substrate by
adding another CdS layers.
The optical properties of CdS thin films were analyzed using
UV/vis spectrometer.
Absorbance
1,2
1,0
0,8
0,6
0,4
0,2
0,0
450 500
Wavelenght (nm)
550
Figure 1. Optical absorption spectra of CdS thin films (a)
minimal molarities of bath concentration (b) maximal molarities
of bath concentration
Figure 1 shows the optical absorptions spectra of the CdS
thin films that were produced using two different molarities of
solution. Figure 2 shows the optical absorption spectra of the
CdS thin films according to deposition times. Figure 3 shows
the optical absorption spectra of the CdS thin films according
to the added CdS layers.
The structural properties were studied by XRD. The surface
morphologies were performed by Scanning Electron
a
b
Absorbance
1,0
0,9
0,8
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0,0
400 450 500
Wavelenght (nm)
550
Figure 2. Optical absorption spectra for the deposition times (a)
10 minutes (b) 20 minutes (c) 30 minutes (d) 50 minutes
Absorbance
4,0
3,5
3,0
2,5
2,0
1,5
1,0
0,5
0,0
450 470 490 510 530 550
Wavelenght (nm)
Figure 3. Optical absorption spectra (a) main layer (b) for
additional one CdS layer (c) for additional two CdS layer
Microscope. The elemental analysis were performed by
Energy Dispersive X-ray spectroscopy
Conclusion
The Energy band gaps of the CdS thin films are
between 2,39 and 2,51 eV,
CdS thin films have cubic zincblende structures
*Corresponding author: 1Tcbaykul@ogu.edu.tr
[1] Vineet Singh and Pratima Chauhan, Journal of Physics and
Chemistry of Solids 70 (2009) 1074–1079
[2] S. Soundeswaran at all, Materials Letters 58 (2004) 2381– 2385
[3] J. Herrero at all, Thin Solid Films 361-362 (2000) 28-33
a
b
c
d
a
b
c
6th Nanoscience and Nanotechnology Conference, zmir, 2010 277