Photolithographically Patterned TiO<sub>2</sub> Films for Electrolyte-Gated Transistors

Valitova, Irina; Kumar, Prajwal; Meng, Xiang; Soavi, Francesca; Santato, Clara; Cicoira, Fabio

doi:10.1021/acsami.6b01922

Cited by 15 publications

(17 citation statements)

References 55 publications

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“…18,19 In particular, the interface between an IL and a porous, nanostructured, or nanocomposite electrode, either at its upper interface with open structure or in the bulk of the porous matrix, is the physical region with the strongest impact on the operation and performance of several state-of-the-art highly miniaturized microelectronic devices. This is likely the case of novel electrolyte-gated field effect transistors, 20,21 or electrolytic supercapacitors, 22−24 but could also be relevant for systems integrating ILs and nanocomposite electrodes based on (bio)polymers for the nascent field of stretchable electronics. 25,26 The incorporation of ILs into a porous solid matrix (usually composed by silica or carbon) resulted in ILs with improved mechanical integrity and ionic conductivity 27−29 because of the interactions between the walls of solid interface and the confined ILs.…”

Section: ■ Introductionmentioning

confidence: 99%

Solid-Like Ordering of Imidazolium-Based Ionic Liquids at Rough Nanostructured Oxidized Silicon Surfaces

2019

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The investigation of ionic liquids (ILs) confined in a solid porous matrix is of particular interest considering that these substances are increasingly used as electrolyte in devices employing nanostructured nanoporous materials for the electrodes. Furthermore, the confinement of the ILs into a porous matrix would allow overcoming the difficulties of its packaging, leakage and portability. In order to support applications, a deeper understanding of the interaction of ILs with the nanoporous solid material and its increased interface is required. In this work, we report on the modification of morphological and mechanical properties of the imidazolium-based [Bmim][NTf2] ionic liquid upon surface confinement on a cluster-assembled nanostructured rough oxidized silicon (ns-SiOx) surface. An atomic force microscopy investigation revealed that upon the interaction with the ns-SiOx film, [Bmim][NTf2] locally rearranges into ordered, layered, stiff and poorly conducting solid-like domains, coexisting with, and embedded into, the liquid IL film. The observed interfacial layering of [Bmim][NTf2] deposited on ns-SiOx suggests that the behavior of the IL-electrode interface in photoelectrochemical devices employing nanostructured nanoporous materials can be far more complex than expected under the hypothesis of an IL-based electrolyte in the stable liquid phase. The observed effects reported in this work could in principle take place also inside the bulk nanoporous matrix, where they could be further amplified by the extreme spatial confinement.

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Section: ■ Introductionmentioning

confidence: 99%

Solid-Like Ordering of Imidazolium-Based Ionic Liquids at Rough Nanostructured Oxidized Silicon Surfaces

2019

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“…Titanium dioxide (TiO 2 ) has attracted tremendous attention because of its unique photocatalytic, photovoltaic, electronic, and optoelectronic properties. [ 1–4 ] The fabrication techniques of TiO 2 arrays and patterns on substrates are important in the large‐area formation of integrated electronics, [ 5 ] memories, [ 6 ] solar cells, [ 7 ] photocatalysis, [ 8 ] sensors, [ 9,10 ] etc. Approaches for TiO 2 thin films including sputtering, [ 11 ] sol–gel, [ 12 ] and chemical vapor deposition [ 13 ] could be used to fabricate TiO 2 patterns on inorganic substrates with the help of photoresist.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of TiO₂ Micropatterns on Flexible Substrates by Vacuum‐Ultraviolet Photochemical Treatments

Soliman

et al. 2020

Adv Materials Inter

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solar cells, [7] photocatalysis, [8] sensors, [9,10] etc. Approaches for TiO 2 thin films including sputtering, [11] sol-gel, [12] and chemical vapor deposition [13] could be used to fabricate TiO 2 patterns on inorganic substrates with the help of photoresist. These methods were conducted in severe reaction conditions, for example, high temperature, and they were usually not applicable to polymer substrates. For flexible devices fabrication, new patterning methods, which can be processed in milder conditions and are adaptable to flexible polymer substrates, are increasingly required. [14] For example, liquid phase deposition (LPD) was proposed as a useful approach for preparing TiO 2 thin films and micropatterns in mild conditions. In this method, the reaction occurred in a liquid solution at room temperature. A soluble titanium precursor was hydrolyzed to form titanium complex ions and condensed to form TiO 2 precipitation. [15,16] Polymer substrates or silicon substrates covered with self-assembled monolayer (SAM) were patterned by UV photolithography to generate affinity patterns; thus, the TiO 2 precipitation on less-affinity regions could be selectively removed to form patterns. Based on this method, TiO 2 micropatterns were successfully fabricated on polymer substrates [17] as well as silicon substrates. [18] However, this method suffered from poor precision because the lift-off process could not precisely remove the TiO 2 on the less-affinity regions.Photolithographic patterning techniques, which can also be conducted in mild conditions, provide new possibilities for the formation of TiO 2 patterns. Vacuum ultraviolet (VUV, 172 nm, Xe 2 excimer lamp) light is strongly absorbed by O 2 , which forms active oxygen species such as ozone and atomic oxygen. [19][20][21][22][23][24][25] VUV light and the active oxygen species (VUV/ (O)) could directly dissociate titanium alkoxide precursors to form amorphous TiO 2 thin films. [19,20] However, such titanium alkoxide precursors are not suitable for operation under an ambient atmosphere because they react with water molecules and the resulting hydrolyzed products are insoluble in common solvents. For micropatterning, choosing a precursor with stable ligands is a key issue related to whether the precursor gels can be clearly removed from the undesired regions.Titanium dioxide (TiO 2 ) micropatterns have received great attention for application in photocatalysis, electronics, and optoelectronics. Formation of such micropatterns on polymer substrates is of importance in flexible device fabrication. Vacuum ultraviolet (VUV) oxidative treatment applied on metalorganic precursor gel films serves as a strategy to fabricate metal oxide films on heat-sensitive substrates such as polymers. Here, 172 nm VUV oxidative treatment through a photomask is used to directly convert the titanium metalorganic precursor films into TiO 2 patterns without further heat annealing. In comparison to the commonly used alkoxide-based precursors, titanium acetylacetonate proves to be an appropri...

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“…Controllable formation of TiO 2 micropatterns is of importance in the design and creation of TiO 2 -based devices. − Several methods were proposed to produce TiO 2 micropatterns including site-selective deposition, , photolithography, and μCP . TiO 2 microarrays were reported to be fabricated on F-doping SnO 2 substrates by a standard μCP process, in which PDMS stamps helped transfer the titania precursor tetrabutyl titanate [TBT, (CH 3 (CH 2 ) 3 O) 4 Ti] as the ink onto the substrates, and further thermal oxidation (>450 °C) resulted in TiO 2 patterns with features larger than 100 μm .…”

Section: Introductionmentioning

confidence: 99%

Microstructured SiO_x/COP Stamps for Patterning TiO₂ on Polymer Substrates via Microcontact Printing

Utsunomiya

Ichii

et al. 2020

Langmuir

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Microcontact printing (μCP) techniques have sparked a surge of interests in microfabrication since they help produce arrays on a wide range of target substrates in a facile and efficient manner. Polydimethylsiloxane (PDMS), as a wellestablished material for stamps, has constraints resulting from its hydrophobicity and softness, and the replication of PDMS stamps usually requires rigid masters or processes using a photoresist. Herein, a novel μCP stamp based on cyclo-olefin polymer (COP) is produced through vacuum ultraviolet (VUV) lithography. 2,4,6,8-Tetramethylcyclotetrasiloxane is selectively deposited at the affinity-patterns on the COP surface, and these patterned siloxane films are converted into SiO x meanwhile protecting the COP beneath them from the VUV photoetching. By this means, a patterned relief is fabricated on the COP plates, resulting in a hydrophilic SiO x /COP μCP stamp with punch heights of ∼180 nm. The novelty arises from the simplicity of the master-and photoresist-free microstructuring, and the higher stiffness of SiO x /COP stamps prevents the deformation during pressing. Finally, an example μCP is given to transfer titania precursor gel and produce TiO 2 micropatterns on flexible polymer substrates. The SiO x /COP stamps and the μCP of TiO 2 provide simple and cost-effective patterning techniques, which should contribute to the future design and creation of flexible devices.

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Photolithographically Patterned TiO₂ Films for Electrolyte-Gated Transistors

Cited by 15 publications

References 55 publications

Solid-Like Ordering of Imidazolium-Based Ionic Liquids at Rough Nanostructured Oxidized Silicon Surfaces

Solid-Like Ordering of Imidazolium-Based Ionic Liquids at Rough Nanostructured Oxidized Silicon Surfaces

Fabrication of TiO₂ Micropatterns on Flexible Substrates by Vacuum‐Ultraviolet Photochemical Treatments

Microstructured SiO_x/COP Stamps for Patterning TiO₂ on Polymer Substrates via Microcontact Printing

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Photolithographically Patterned TiO2 Films for Electrolyte-Gated Transistors

Cited by 15 publications

References 55 publications

Solid-Like Ordering of Imidazolium-Based Ionic Liquids at Rough Nanostructured Oxidized Silicon Surfaces

Solid-Like Ordering of Imidazolium-Based Ionic Liquids at Rough Nanostructured Oxidized Silicon Surfaces

Fabrication of TiO2 Micropatterns on Flexible Substrates by Vacuum‐Ultraviolet Photochemical Treatments

Microstructured SiOx/COP Stamps for Patterning TiO2 on Polymer Substrates via Microcontact Printing

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Product

Resources

About

Photolithographically Patterned TiO₂ Films for Electrolyte-Gated Transistors

Fabrication of TiO₂ Micropatterns on Flexible Substrates by Vacuum‐Ultraviolet Photochemical Treatments

Microstructured SiO_x/COP Stamps for Patterning TiO₂ on Polymer Substrates via Microcontact Printing