Abstract
We present here a novel resist formulation with active thiol groups at the surface. The material is UV curable, and can be patterned at the micro- and nanoscale by UV nanoimprint lithography. The resist formulation development, its processing, patterning and surface characterization are presented here. In addition, a possible application, including its use to modify the electrical properties of graphene devices is shown. The cured material is highly transparent, intrinsically hydrophilic and can be made more hydrophilic following a UV-ozone or an O2 plasma activation. We evaluated the hydrophilicity of the polymer for different polymer formulations and curing conditions. In addition, a protocol for patterning of the polymer in the micro and nanoscale by nanoimprinting is given and preliminary etching rates together with the polymer selectivity are measured. The main characteristic and unique advantage of the polymer is that it has thiol functional groups at the surface and in the bulk after curing. These groups allow for direct surface modifications with thiol-based chemistry e.g., thiol-ene reactions. We prove the presence of the thiol groups by Raman spectroscopy and perform a thiol-ene reaction to show the potential of the easy “click chemistry”. This opens the way for very straightforward surface chemistry on nanoimprinted polymer samples. Furthermore, we show how the polymer improves the electrical properties of a graphene field effect transistor, allowing for optimal performance at ambient conditions.
Highlights
Nanoimprinting lithography (NIL) has emerged over the last two decades as a high throughput nanofabrication method and is a consolidated technology [1,2,3]
We prove the presence of the thiol groups by Raman spectroscopy and perform a thiol-ene reaction to show the potential of the easy “click chemistry”
We show how the polymer improves the electrical properties of a graphene field effect transistor, allowing for optimal performance at ambient conditions
Summary
Nanoimprinting lithography (NIL) has emerged over the last two decades as a high throughput nanofabrication method and is a consolidated technology [1,2,3]. In recent years a strong industrially-driven research can be observed, pushing NIL and its applications from purely academic purposes to innovations in data storage, point of care diagnostics, electronic and graphene devices or augmented reality [4,5,6,7,8,9] With this shift, new materials need to be developed with properties that are compatible with mass production: fast curing and imprinting, robustness, reproducibility, and patterning on flexible substrates, both, at the micro and nano scale. A new trend has emerged towards direct patterning of functional materials, where the imprinted structures are directly used as active elements in devices These devices find applications in several different fields, like micro and nanofluidics [11,12], biosensing [13] and DNA analysis [14], optical, nanophotonic [15] and flexible, electrical devices [16]. As a second possible application, we show how the polymer, just placed on top of a graphene device, changes its electrical properties and allows for operation at ambient conditions, without ultra-high vacuum
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