1. THE EFFECT OF SPIN COATING RATE ON MICROSTRUCTURES OF CUPROUS OXIDE THIN FILM PREPARED BY SOL-GEL TECHNIQUE
DEWI SURIYANI BT CHE HALIN
School of Material Engineering
Perlis University of Malaysia
MALAYSIA
A PhD Student Physics Program Faculty of Science and Technology National University of Malaysia MALAYSIA

2. OUTLINE INTRODUCTION EXPERIMENTAL RESULT AND DISCUSSIONS CONCLUSIONS
ACKNOWLEDGEMENT

3. INTRODUCTION Copper forms two well known oxides; (1) Cu2O (2) CuO
Cu2O - an interesting p-type semiconductor.
- direct energy gap of eV.
- promising material in solar energy applications.
- nontoxic and low cost to produce.
- cubic structure with a lattice parameter of Å.

4. Cu2O leads to become a promising material in solar energy applications.
Various methods were used to prepared Cu2O thin films;
Sputtering
Thermal oxidation
Electrodeposition
Vacuum evaporation
Sol-gel process

5. Sol-gel spin coating requires considerably;
Less equipment
Low cost production
Simple
Effective way of
making thin films with varying
its thickness by just controlling parameters.

6. EXPERIMENTAL Copper (II) acetate Isopropyl alcohol Mixed continuously
Add small amount of glucopone
Stirring using magnetic bar for 24 hours
Filtered using 0.45 μm filter
Spin coating
Annealing (350 ˚C)
Cuprous oxide films
Diethanolamine (DEA)
Dried in oven
Repeated for 2 layers of coating
5% H2 95% N2

7. CHARACTERIZATION Microstructure of films X-ray diffractometer
Scanning electron
microscopy
Morphology of films
Ultraviolet-visible
spectroscopy
Optical properties
X-ray photoelectron
spectrometer
Chemical state of films

8. X-RAY DIFFRACTOMETER
a crystalline cubic Cu2O film with two peaks, (111) and (200).
mineral cuprite,Cu2O (JCPDs card no ).

9. SCANNING ELECTRON MICROSCOPYb c
2000 rpm, 61 nm
4000 rpm, 49 nm
6000 rpm, 40 nm
All films exhibit a smooth continuous film.
The films were in orderly form consisting fine grains of rounded shape.

10. The average thickness of the films measured using the scanning electron microscopy are 108 nm, 64 nm and 62 nm for spinning rates of 2000, 4000 and 6000 rpm, respectively.
The lower the spinning rate, the thicker the film.

11. X-RAY PHOTOELECTRON SPECTROMETER
Binding energy (eV)
Intensity (cps)
C KLL
Cu 2p
O KLL
O 1s
Cu LMN
C 1s
Cu 3s
Cu 3p
Cu 2p1/2 = eV

12. The survey scan shows the presence of copper, oxygen and a small carbon peaks.
The Cu 2p1/2 peak binding energy of 932.4eV shows excellent agreement with the value of eV quoted in the literature.
No other phases detected by XPS which is in good agreement with the GAXRD pattern.

13. ULTRAVIOLET-VISIBLE SPECTROSCOPY
High absorbance
Low spinning rate
Thickest film
High spinning rate
Thinnest film
Low absorbance

14. The optical band gap increased with spinning rate.
Table 1. The relationship between optical properties, spin rate and grain size of cuprous oxide films prepared by sol-gel technique.
Spinning rate
(r.p.m)
Grain size
(nm)
Thickness
Optical band gap
(eV)
2000 61
108
2.08
4000 52 64
2.16
6000 45 58
2.20
The optical band gap increased with spinning rate.
The increasing in grain size of film with decreasing of spinning rate will also contribute to the reduction in optical transparency through optical scattering.

15. CONCLUSIONS
Cuprous oxide films have successfully been deposited on indium tin oxide (ITO) substrates by a sol-gel spin coating technique using copper (II) acetate.
The lower spin rate was able to produce a thicker film compared to the film obtained at higher spin rate.
The thickest film (108 nm) with high absorbance is potentially suitable for a photoelectrochemical solar cell application.

16. ACKNOWLEDGEMENT
The authors gratefully acknowledge the financial support by MOSTI, through Science Fund grant No SF0211.
Perlis University of Malaysia (UniMAP) for the PhD scholarship (Feb 2006-August 2009)

17. THANK YOU FOR YOUR ATTENTION