Self-organized nanostructured anodic oxides for display applications
Electrochemical technologies have a high potential for display applications because of their cheapness and simplicity, easiness to scaling to large substrates and lowtemperature nature. However, in major display technologies the oxide films should be deposited on transparent conductive substrate,...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
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irk-123456789-1183902017-05-31T03:07:04Z Self-organized nanostructured anodic oxides for display applications Jaguiro, P. Stsiapanau, A. Hubarevich, A. Mukha, Y. Smirnov, A. Electrochemical technologies have a high potential for display applications because of their cheapness and simplicity, easiness to scaling to large substrates and lowtemperature nature. However, in major display technologies the oxide films should be deposited on transparent conductive substrate, usually ITO on glass. For dielectric substrates like glasses, a special technology of current control is applied to anodizing metal films, which changes the oxide porous structure in a final stage and prevents formation of metal islands. To transform the residual metal nanowires into oxide, a special fading process similar to anoding bonding can be done. Usually, high reactivity electrolytes are used in the anodizing process, which destroys ITO layers. We have analyzed chemical properties of ITO in various anodizing electrolytes and found some suitable reagents and compositions. A lot of functional layers can be created by anodizing. For example, different filters may be formed by filling the pores by ink jet printing. Porous oxides can have low refractive indexes – lower than any bulk material, and can be used as effective antireflective coatings. A titanium oxide cover film forms “self-cleaning” surface due to its semiconductor photonics properties and oxygen production. 2010 Article Self-organized nanostructured anodic oxides for display applications / P. Jaguiro, A. Stsiapanau, A. Hubarevich, Y. Mukha and A. Smirnov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2010. — Т. 13, № 3. — С. 305-308. — Бібліогр.: 15 назв. — англ. 1560-8034 PACS 81.05.Rm, 82.45.Yz, 82.47.Tp http://dspace.nbuv.gov.ua/handle/123456789/118390 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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Electrochemical technologies have a high potential for display applications
because of their cheapness and simplicity, easiness to scaling to large substrates and lowtemperature
nature. However, in major display technologies the oxide films should be
deposited on transparent conductive substrate, usually ITO on glass. For dielectric
substrates like glasses, a special technology of current control is applied to anodizing
metal films, which changes the oxide porous structure in a final stage and prevents
formation of metal islands. To transform the residual metal nanowires into oxide, a
special fading process similar to anoding bonding can be done. Usually, high reactivity
electrolytes are used in the anodizing process, which destroys ITO layers. We have
analyzed chemical properties of ITO in various anodizing electrolytes and found some
suitable reagents and compositions. A lot of functional layers can be created by
anodizing. For example, different filters may be formed by filling the pores by ink jet
printing. Porous oxides can have low refractive indexes – lower than any bulk material,
and can be used as effective antireflective coatings. A titanium oxide cover film forms
“self-cleaning” surface due to its semiconductor photonics properties and oxygen
production. |
| format |
Article |
| author |
Jaguiro, P. Stsiapanau, A. Hubarevich, A. Mukha, Y. Smirnov, A. |
| spellingShingle |
Jaguiro, P. Stsiapanau, A. Hubarevich, A. Mukha, Y. Smirnov, A. Self-organized nanostructured anodic oxides for display applications Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Jaguiro, P. Stsiapanau, A. Hubarevich, A. Mukha, Y. Smirnov, A. |
| author_sort |
Jaguiro, P. |
| title |
Self-organized nanostructured anodic oxides for display applications |
| title_short |
Self-organized nanostructured anodic oxides for display applications |
| title_full |
Self-organized nanostructured anodic oxides for display applications |
| title_fullStr |
Self-organized nanostructured anodic oxides for display applications |
| title_full_unstemmed |
Self-organized nanostructured anodic oxides for display applications |
| title_sort |
self-organized nanostructured anodic oxides for display applications |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| publishDate |
2010 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/118390 |
| citation_txt |
Self-organized nanostructured anodic oxides for display applications / P. Jaguiro, A. Stsiapanau, A. Hubarevich, Y. Mukha and A. Smirnov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2010. — Т. 13, № 3. — С. 305-308. — Бібліогр.: 15 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
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| first_indexed |
2025-07-08T13:53:25Z |
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2025-07-08T13:53:25Z |
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| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 3. P. 305-308.
PACS 81.05.Rm, 82.45.Yz, 82.47.Tp
Self-organized nanostructured anodic oxides for display applications
P. Jaguiro, A. Stsiapanau, A. Hubarevich, Y. Mukha and A. Smirnov
Belarusian State University of Informatics and Radioelectronics,
Laboratory of Information Displays,
6, P. Brovki str., 220013 Minsk, Belarus
Abstract. Electrochemical technologies have a high potential for display applications
because of their cheapness and simplicity, easiness to scaling to large substrates and low-
temperature nature. However, in major display technologies the oxide films should be
deposited on transparent conductive substrate, usually ITO on glass. For dielectric
substrates like glasses, a special technology of current control is applied to anodizing
metal films, which changes the oxide porous structure in a final stage and prevents
formation of metal islands. To transform the residual metal nanowires into oxide, a
special fading process similar to anoding bonding can be done. Usually, high reactivity
electrolytes are used in the anodizing process, which destroys ITO layers. We have
analyzed chemical properties of ITO in various anodizing electrolytes and found some
suitable reagents and compositions. A lot of functional layers can be created by
anodizing. For example, different filters may be formed by filling the pores by ink jet
printing. Porous oxides can have low refractive indexes – lower than any bulk material,
and can be used as effective antireflective coatings. A titanium oxide cover film forms
“self-cleaning” surface due to its semiconductor photonics properties and oxygen
production.
Keywords: transparent and functional layers, displays, photonics, electrochemical
anodizing.
Manuscript received 18.12.09; accepted for publication 08.07.10; published online 30.09.10.
1. Introduction
Electrochemical technologies have a high potential for
displays and photonics applications because of its
cheapness and simplicity, easiness to scaling to large
substrates and low-temperature nature [1]. However,
electrochemical processes at higher temperatures when
glass substrates remain solid but get some ionic
conductivity can provide a drastically wide range of
possible applications.
Both displays and photonic devices operate
with transparent substrates and layers, therefore, from
the practical point of view, anodizing technologies for
Al, Ti and W foils and thin films can be interesting. The
anodic oxides of metals are widely used in displays and
photonics for vertical alignment of liquid crystals [2],
polarizers [3], optical filters [4], self-cleaning glasses
[5], sensors [6], photolysis and electrochromic devices
based on valve metal oxide layers [7], fading created
oxide layers and carrying out anodizing processes over
transparent conductive films is a point of intense interest
for researchers and engineers.
Some anodic nanoporous oxides like TiO2 and
WO3 possess semiconductor properties that can be
effectively used in displays and photovoltaic
applications. However, processes of their formation and
especially through anodizing over ITO layers are not
sufficiently investigated and clear up to date. A primary
goal of this work is to investigate foil to glass anodic
bonding technology, because anodic bonding is well
known [8] to provide excellent adhesion and vacuum
sealing quality. However, to bond bulk metal, the glass
with correspondent thermal expansion should be used.
For Al correspondent glasses are absent at all, for Ti and
W correspondent glasses get ionic conductivity only at
rather high temperatures. But for the metal foils due to
their high elasticity, it is possible to use metal-glass
systems with a significant difference in thermal
expansion [9]. Particularly, it is possible to use sodium
glasses and aluminum foil [10]. Note that for Ti and W
foils special surface treatment is needed. The process of
foil to glass anodic bonding is illustrated in Fig. 1. For
aluminum foil and sodium glass, the bonding process
takes about 10 minutes at 270-300 °C and ~5 mA/cm2
© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
305
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 3. P. 305-308.
current density provided with the negative 1200-1600 V
bias at high voltage electrode. It is necessary to polish
foil for the best adhesion. However, polishing is not
enough to achieve well organized honeycomb structure
of anodic oxide (Fig. 2).
Thermal annealing of the foil is more important
for the best pore organizing.
© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
Fig. 1. Scheme of anodic bonding.
Fig. 2. Anodized polished Al foil.
Fig. 3. Nanosponge structure of WO3.
2. Through anodizing the metal films on insulator
substrates
When anodizing foil, it appears that a lot of metal
islands remains at the interface between isolated
substrate and anodic oxide. The reason is local
differences in the foil thickness and anodizing current. If
islands are created, the anodizing process is stopped at
the moment, because of current interruption. Special
technology of current control is applied to anodizing
metal films on insulator substrates, which changes the
oxide porous structure in the final stage and prevents
formation of metal islands. An additional factor that
lowers transparency of the film is presence of many
vertical metal nanowires in anodic oxides [11]. It is very
good for polarizes, but bad for transparency. To
transform the nanowires into oxide, a special fading
process similar to anoding bonding can be done [12]. It
is possible to create a lot of functional layers by filling
the pores, for example, by ink jet printing [13]. Note that
porous oxides can possess low refractive indexes – lower
than those of any bulk materials, and can be used as
effective antireflective coatings. Titanium oxide cover
film forms “self-cleaning” surface due to its
semiconductor photonics properties and oxygen
production.
Heated metal plate
Foil
Glass
High voltage electrode
3. Through anodizing the metal films on transparent
conductive substrates
For display technologies and photonics, the oxide films
should be deposited on transparent conductive substrate,
usually ITO on glass. However, high reactivity
electrolytes are used in the anodizing process, which
destroys ITO layers. We have analyzed chemical
properties of ITO in different anodizing electrolytes and
found some suitable reagents and compositions.
Mechanisms of ITO passivation have been discussed in
details. Current voltage characteristics of anodic ITO
dissolution have been presented and analyzed.
Overheating and gas evolution as destroying factors
have been under consideration, too.
In Fig. 3, nanosponge structure of WO3
anodized in ITO compatible electrolyte is presented.
4. Porous alumina template masking
It is possible to achieve many useful structures by
anodizing the bi-layer structures, where top porous
anodic oxide is used as a template for anodizing or
etching the bottom layer. For example, titania columnar
structure [1] and ultra-black silicon can be formed [14].
Masking makes easier the pore nucleation process in the
bottom layer, therefore more regular porous structures in
less aggressive electrolytes can be formed in the bottom
layer.
306
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 3. P. 305-308.
5. Transparent conductive aluminum nanomesh
It is possible to form a transparent conductive aluminum
nanomesh on glass substrate from thin aluminum layer
by simple anodizing process. The anodizing parameters
are changed in the final stage of the process [15], which
allows to open transparent windows and leave a
nanomesh from aluminum residues (see Fig. 4).
© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
SEM photo of the aluminum nanomesh after
selective etching the Al2O3 skeleton is presented in
Fig. 5.
In the nanomesh, transparent and conductive
functions are separated in space, but this feature doesn’t
come out due to a sub-wavelength size of the nanomesh
pitch. It allows overcoming some fundamental
limitations that are specific to ITO and ultra-thin metal
films, where conduction electrons operate as electric
charge carriers and light absorbers simultaneously.
In Fig. 6, geometrical structure of the nanomesh
and correspondent theoretical results (resistance and
transmittance for different pitch values) are presented.
Fig. 4. Structure of the transparent conductive nanomesh.
Fig. 5. SEM photo of the aluminum nanomesh.
Fig. 6. Geometrical structure and correspondent theoretical
calculations for the nanomesh.
6. Conclusion
Electrochemistry based technologies to fabricate
transparent porous anodic alumina layers and aluminum
nanomesh, which can work as alignment layers, color
filters, light absorbers and transparent conductive films
have been proposed. These technologies are simple,
cheap, low-temperature and scalable to large substrates
and roll-to-roll techniques.
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© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
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