minimum parameters necessary for grow a thin film with a sol

MACROMEX 2014
MINIMUM PARAMETERS NECESSARY FOR GROW A THIN FILM
WITH A SOL-GEL METHOD
O. Ortiz-Jimenez,1* D. A. Razo-Medina,2 ,M. Trejo-Durán,1 E. Alvarado-Méndez, 2 R. I.
Mata-Chávez 1, Martínez Rosales M.3
1
Departamento de Estudios Multidisciplinarios (DEM), Universidad de Guanajuato, Yuriria, Gto. México.
2
División de Ingenierías, Campus Irapuato-Salamanca (DICIS), Universidad de Guanajuato, Com. Palo
Blanco s/n 36885, Salamanca, Gto. México
3
División de Ciencias Naturales y Exactas, Campus Guanajuato, Universidad de Guanajuato.
Noria alta s/n 36050, Guanajuato, Gto. México.
* [email protected]
Abstract
In this work is presented the result of the conditions for grow a thin film with a sol-gel method and with the aid of
a dip-coater. The conditions are like preparation of sol-gel, temperature, atmosphere, cycles of immersion, drying
of the film, etc., of which here show only the principal variables that is relatively easy to controlled in the section
of methodology. Finally, in the section of results we perform the final thin film and the first studies.
Introduction
In the literature there are different techniques for growing films for example sputtering, pulsed
laser deposition, and more. When compared with others techniques, the sol-gel presents some
advantages such as possibility of depositing in complex-shaped substrates as well as it requires
considerably less equipment and is potentially less expensive [1,2].
This technique is useful for example to make a WO 3 and W-Ti-O thin-film gas sensors [3],
preparation, characterization and gas-sensing property of thin-film of ZnO [4].
Third US-Mexico Meeting “Advances in Polymer Science” and XXVII SPM National Congress
Nuevo Vallarta, December 2014
MACROMEX 2014
Dip coating by sol-gel process is versatile and low-cost techniques strategies to prepare thin
films of particles. In general form, the sol-gel coating consists in dip a substrate in a fluid gel:
solvent evaporation and gravitational draining, more condensation reactions, result in the
deposition of a solid film [5].
Methodology
For this work, many different experiments are performed for creating a thin film over glass
substrate. The project was divided into two stages, the first stage is the sol-gel mixture, different
tests are made to modify parameters of the mixture. The second stage of the film is made with
the dip-coater device.
The chemicals used in the sol-gel were Tetraethyl Orthosilicate (TEOS), Ethanol and Water, at a
ratio of 4:4:1 respectively. The rates were obtained from a previous work [japs2006]. The next
step was to determine the ideal viscosity for the mixture. As we know, there are different factors
that affect the chemical reaction, for example temperature, humidity, mole ratios between
reactants, and others. In order to determine the viscosity of the mixture, it was left to evaporate at
room temperature. After that, we started to make a film and we observed the behavior of the
mixture with the substrate.
a)
b)
Figure 1. a)Mixture after 24 hours of environmental evaporation. b)Film obtain with the previous mixture
Third US-Mexico Meeting “Advances in Polymer Science” and XXVII SPM National Congress
Nuevo Vallarta, December 2014
MACROMEX 2014
With the help of a dip-coater, which was encapsulated in a glass chamber, the immersion of the
substrate was controlled over the mixture. Due the evaporation of the mix, it was necessary to
control it; we saturated the chamber environment with ethanol at 70 ºC.
The next step was to determine the appropriate speed for the dip-coater. The dip coater is like the
one in figure 2. With this variable, we tried with low speed, but in the literature we find that it is
better to use fast speed [2]. The fastest speed the dip coater could offer was 61.14 mm/min, so it
was the fastest speed to work with and it was also the best.
Figure 2. Dip coater mono.
The next step is to determine the appropriate number of cycles of immersion of the substrate in
the mixture. We started with 15 and 30 cycles, but the thickness was not appropriate. We
obtained an acceptable homogeneous film at 100 cycles. With the 100 cycles as a starting point,
the next step was to create a thicker film. This was obtained when we increased the number of
cycles to 150 and 200 cycles.
Once we had the film, the next challenge was the drying process. We found out that the films
needed to remain almost three days in the chamber to be completely dried. With this time, it is
possible to obtain a film that will not break when exposed in environmental conditions, without
having to give any heat treatment.
Third US-Mexico Meeting “Advances in Polymer Science” and XXVII SPM National Congress
Nuevo Vallarta, December 2014
MACROMEX 2014
Results
In the figure 3 we show the evolution of the film when we increase the number of cycles. In
each case we keep the same mixture and speed.
c)
a)
b)
Figure 3. Evolution of the film. a) 30 cycles b) 100 cycles c) 200 cycles
Once we had the film, we took photos of the film with an optical microscope and we found the
existence of a little pore. The reason for the existence of the pores is due to the fact that the
solvent needed to find a way to leave the film.
Once the speed was determined, the next step was to start increasing the number of cycles, such
as is shown in figure 3 with more cycles. The film is more homogeneous and presents less pores
or fractures, but when we increasing the cycles, the time in the chamber increases too.
Conclusions
In this work we focused on the manufacturing process and deposition of sol-gel film on glass
substrate. The films were analyzed using optical microscopy. We determined the minimum
parameters necessary to manufacture good thin films with other components like nanoparticles,
coordinate compounds, among others using the sol-gel method.
Third US-Mexico Meeting “Advances in Polymer Science” and XXVII SPM National Congress
Nuevo Vallarta, December 2014
MACROMEX 2014
Acknowledgements
This work was supported partially by Guanajuato University-DAIP No. 223/2013, 288/ 2013 and
PIFI-2013.
References
[1] C. J. Brinker, G. C. Fryem A. J. Hurd and C. S. Ashley, Thin Solid Films, 201, 97-108 (1991).
[2] M.H. Habibi and M. Khaledi Sardashti (2007), Structure and Morphology of Nanostructured
Zinc Oxide Thin Films Prepared by Dip-vs. Spin-Coating MethodsJ. Iran. Chem. Soc., Vol. 5,
No. 4, December 2008, pp. 603-609.
[3] J. Shieh, H.M. Feng, M.H. Hon, H.Y. Juang (2002), WO 3 and W-Ti-O thin-film gas sensors
prepared by sol-gel dip-coating, Sensors and Actuators B 86 (2002) 75-80
[4] X.L. Cheng, H. Zhao, L.H. Huo, S. Gao, J.G. Zhao (2004), ZnO nanoparticulate thin film:
preparation, characterization and gas-sensing property, Sensors and Actuators B 102 (2004)
248–252.
[5] N. V. Kaneva, C. D. Dushkin (2011). Preparation of nanocrystalline thin films of ZnO by
sol-gel dip coating. Bulgarian Chemical Communications s, Volume 43, Number 2 (pp.
259–263).
Third US-Mexico Meeting “Advances in Polymer Science” and XXVII SPM National Congress
Nuevo Vallarta, December 2014