Special optical fibers and fiber capillaries coated with Indium-Tin-Oxide
1. UTB 2012
Vladimír Bobuský, Jan Mrázek, Ondřej Podrazký
Institute of Photonics and Electronics ASCR v.v.i,
Chaberská 57, 182 51 Prague, Czech Republic
Special optical fibers and fiber
capillaries coated with
Indium-Tin-Oxide
3. Goals
UTB 2012
SPIE 2013
• Preparation of ITO thin films from colloidal solution by dip-
coating method
• Characterization of electrical and optical properties and
comparison to other methods
4. Widely used transparent semiconductor
• Electrically conductive
• Optically transparent
Huge applications in markets:
Introduction – Indium-Tin-Oxide (ITO)
SPIE 2013
OLEDTouch panelsFlat panel displays Solar Cells
5. Preparation of ITO thin films
Chemical depositionPhysical deposition
Advantage & Drawbacks Phys Chem Colloids
Well tailored thickness
Application inside cavities
Large deposition area
Quick preparation
• Magnetron sputtering • Chemical approaches
• Deposition of colloids
SPIE 2013
7. Deposition
• Proportionality of ITO film thickness and the withdrawing speed
SPIE 2013
0 50 100 150 200
200
250
300
350
400
450
500
550
Thickness(nm)
Withdrawing speed (mm⋅min
-1
)
• The withdrawing speed is the most flexible parameter
9. SPIE 2013
• Temporal variation of the resistivity
• Investigation of factors responsible for the changing resistivity
Electrical properties – Temporal stability
10. UTB 2012
SPIE 2013
• Resistivity relative changes due to concentration of water in
atmosphere
4 6 8 10 12 14 16 18
100
200
300
400
500
600
Relativechangesoftheresistivity(%)
Partial pressure of water (kPa)
• Porosity of prepared ITO films
Electrical properties – Humidity interferences
11. UTB 2012
SPIE 2013
• High porosity showed by AFM and SEM
Morfology of prepared films
• Imprinted nanoparticles shape
AFM scan of ITO film
SEM of ITO film
12. UTB 2012
SPIE 2013
• Calculated Refractive index
• Value of the refractive index is lower than the value 2,0
400 500 600 700 800
1.4575
1.4580
1.4585
1.4590
1.4595
1.4600
Refractiveindex
Wavelength (nm)
n( λ)=A+
B
λ2
+
C
λ4
Optical properties – Spectral ellipsometry
Cauchy’s dispersion relations
3,4
[3] Vacuum, paper 1191, (1994), 45 (12)
[4] Japanese Journal of Applied Physics, (2009), 48
n –refractive index
A, B, C, - fitted constants
λ -wavelength
n = 1,457 for λ = 632 nm
13. Planar substrate
UTB 2012
SPIE 2013
• Refractive index of layer n = 1,46
• High porosity of ITO layer 54% pores in coated films
Theory of effective media:
14. Electrical properties – Optical fibers
UTB 2012
SPIE 2013
0 30 60 90 120 150 180
0
5
10
15
20
25
Resistance(MΩ)
Length (mm)
• Preparation method of ITO films alike on planar substrates
• The optical fiber with diameters lower than 250μm and
inhomogenous ITO layers
• High resistance of ITO films coated on the fibers
15. Optical properties – Optical fibers
UTB 2012
SPIE 2013
-30 -20 -10 0 10 20 30
0.0
0.2
0.4
0.6
0.8
1.0 ITO coating
PCS fiber
Normalizedoutputpower
Angle of incidence (deg)
Angular distribution of output power – numerical aperture (NA)
• The calculated value of numerical aperture for PCS fiber
• Refractive index of ITO cladding
NA=√ncore
2
−ncladding
2
NA = 0,1078
16. UTB 2012
SPIE 2013
Summary
High resistivity
Planar substrate 0,11 Ω*mm
Optical fiber 150 MΩ*mm
Colloidal solution ITO
High adsorption properties
Large surface area
High porosity 54%
Refractive index n = 1,457
17. UTB 2012
SPIE 2013
General Conclusions
Colloidal solution ITO
• ITO thin films prepared on planar substrates and optical fibers by
dip-coating
• Easy and quick preparation of films with determined thickness
• Strong dependence of the resistivity on the humidity
• Preparation inside of capillaries and on the optical fibers
• Homogeneity of ITO layers
• Suitable for sensors
18. UTB 2012
SPIE 2013
Thank you for your attention
Acknowledgement:
The research was supported by the Grant Agency of the Czech
Republic, project No. 102/10/2139
I thank to my collegues Petra Lebrušková and Zdeňěk Jarchovský for
their help with AFM and SEM analysis.
19. Characterization of ITO films
UTB 2012
SPIE 2013
Multimeter
TD2000
Profilometer
Tercor Alfa
Ellipsometery
Sentech 850SE spectral ellipsometer
RTA
AFM
SEM
Lyra 3 Tescan
First of all, I would like to initiate you into the field of ITO films
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Charakterizace vrstev – Porovnání
As you already know
The ITO film are usually prepared by the sophisticated methods…
Colloidal solution of ITO nanoparticles dispersed in isopropanol was used to prepare thin films.
As we expected
Resistivity monotonously decrease
Relative changes of resistivity was mainly influenced by concentration of water in atmosphere
Increasing concentration of water cause the increasing resistivity
AFM and SEM show the high porosity of the prepared films
Water is absorbed inside pores of ITO films and affects the conductivity
The nanoparticles shape is imprinted to the layer
Pro 632 nm – udává se.
Preparation of ITO film on the planar substrates are highly reproducible
The ITO layers are homogenous
This theory has a logical implication that the final refractive index is a linear combination of both refractive indexes of solid ITO and air, depending on molar fraction of particular phase in substance
x –molar fraction of particular phase
Upravit obrázek – air 1,0
ito – 2.0
ITO films on optical fibers were prepared alike on planar substrates
No homogenous ITO layers were coated on the fiber with diameters lower than 250μm – sufrace tension – inappropriate adhesion
The value of numerical aperture for PCS fiber and refractive index of ITO cladding were calculated
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Strong dependence of the resistivity of prepared ITO films on the humidity was observed
The resistivity of prepared optical fiber and planar substrate were below 0,15 MΩ*m and 0,00011 Ω*m
Refractive index of prepared films was 1,458
Strong dependence of the resistivity of prepared ITO films on the humidity was observed
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Vyjmenovat pozitiva
Schůdnost
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Charakterizace vrstev – Porovnání
