XXIX Panhellenic Conference on Solid State Physics & Materials Science
22-25 September 2013, Athens, Greece
Sol Gel grown compound ZnO:Au Thin Films for
Optoelectronics and Gas Sensing Application
P. KORALLI1,2*, G. MOUSDIS1, M. KOMPITSAS 1, D. E. MANOLAKOS2
1National
Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vasileos Constantinou Avenue, 11635 Athens, GREECE
of Mechanical Engineering, National Technical University of Athens, Iroon Polytechniou 9 Zografos, 15780 Athens, GREECE
2School
3
*www.laser-applications.eu, [email protected], [email protected]
Abstract
Results - Observations
Gold doped zinc oxide thin films were deposited onto microscope
100
 Optical
glass by the sol–gel spin coating technique. The Au concentration was
80
morphological studies on the ZnO and ZnO:Au thin films have been performed
by using Atomic Force Microscopy (AFM). The optical properties of the
Transmission (%)
varied from 0 to 10 w/w% using an 0.03M HAuCl4 ethanolic solution. The
samples structure was studied by X-ray diffraction (XRD). Topographical and
spectrophotometer.
60
 The
40
Furthermore, the sensing properties of the doped films, as a function of the
ZnO:Au 2.5%
ZnO:Au 5%
ZnO:Au 7.5%
ZnO:Au 10%
ZnO (without Au)
0
400
Au concentration were investigated.
increase
of
gold
concentration
improves the average film transmission.
20
prepared thin films were investigated and analysed.
transmission spectra were recorded
in the 300 – 1200 nm range with a UV-Vis
600
800
1000
 Increasing the gold concentration, we
obtained better results for the SPR of Au.
1200
Wavelength (nm)
Films growth – Spin coating technique
Fig 4: Optical transmission spectra of ZnO and ZnO:Au thin films
ZnO:Au, annealed
60
ZnO (100)
55
50
ZnO (101)
45
X-ray Diffractogram:
AuZn3
ZnO (002)
40
 Indication of the (101), (002) and (100)
Intensity
35
 The thin film is mainly amorphous.
30
25
20
15
diffraction peaks of ZnO.
10
5
0
30
32
34
36
38
2 theta (degr.)
Fig 5: XRD pattern of ZnO:Au thin film
 The topography and morphology of the
films studied by AFM.
Fig 1: Thin films growth using the sol gel spin coating technique
 Formation
 The surface shows a “worm – like”
of ZnO and ZnO:Au thin films onto microscope glass
 Zinc acetate dihydrate (Zn(CH3COO)22H2O) dissolved in the
structure.
Fig 6: 2D and 3D AFM images of ZnO thin film .
 The embodiment of Au in the ZnO
mixture of isopropanol and 2-amino-ethanol.
matrix, decreases the diameter of these
 The Au concentration was varied from 0 to 10 w/w% using an
“worm-like” structures relative to undoped
0.03M HAuCl4 ethanolic solution.
ZnO films.
 This “worm-like” surface structure favors
gas sensing, because it increases the active
Fig 7: 2D and 3D AFM images of ZnO:Au thin film .
surface.
1.0
1620 ppm
0.9
Fig 2: ZnO:Au (left) and ZnO thin films on glass substrate prepared by sol – gel spin
coating technique
 ZnO is an n-type semiconductor.
 The insertion of 5%wt. Au in the ZnO solution
responded to acetone gas at concentrations as low as
Film thickness ~ 200 nm
110 ppm/air, at 180 – 200oC operating temperature.
Relative conductivity (dI/Io)
2140 ppm
0.8
815 ppm
0.7
416 ppm
140 ppm
0.6
2540 ppm
200 ppm
0.4
air
air
0.3
air
Acknowledgment
This work is supported by the Greek General Secretariat for Research and
Technology under the MS/AC S&T ERA.Net RUS program, STProjects-212,
FilmSolar.
Fig 3: Profilometer measurement of the thickness of the ZnO:Au thin film
110 ppm
0.5
air
air
air
air
0.2
4000
6000
8000
10000 12000 14000 16000 18000 20000 22000
Time (sec)
Fig 8: Time evolution of ZnO:Au sensor response relative
to acetone concentration.