Fabrication of High-Performance Ultrathin In₂O₃ Film Field-Effect Transistors and Biosensors Using Chemical Lift-Off Lithography

Abstract

We demonstrate straightforward fabrication of highly sensitive biosensor arrays based on field-effect transistors, using an efficient high-throughput, large-area patterning process. Chemical lift-off lithography is used to construct field-effect transistor arrays with high spatial precision suitable for the fabrication of both micrometer- and nanometer-scale devices. Sol-gel processing is used to deposit ultrathin (∼4 nm) In2O3 films as semiconducting channel layers. The aqueous sol-gel process produces uniform In2O3 coatings with thicknesses of a few nanometers over large areas through simple spin-coating, and only low-temperature thermal annealing of the coatings is required. The ultrathin In2O3 enables construction of highly sensitive and selective biosensors through immobilization of specific aptamers to the channel surface; the ability to detect subnanomolar concentrations of dopamine is demonstrated.

Aptamer Recognition of Multiplexed Small-Molecule-Functionalized Substrates

“…Cross-reactivity of the dopamine aptamer for norepinephrine, for which L- DOPS is the precursor, has been previously reported and is presumably due to aptamer recognition largely involving the catechol moiety present in these highly similar targets. 35,38,48,49 Minimal relative fluorescence was observed for the L -5-HTP pre-functionalized thiol, similar to the specificity of this dopamine aptamer for tethered dopamine vs. L -tryptophan (Figures 3, 4). …”

“…the dopamine aptamer investigated here). 35,36,48,49 These difficulties have been attributed to the complexity in targeting molecules with low molecular mass and rotatable bonds. 59,60 Recent advances in solution-phase SELEX methods that obviate tethering targets have enabled identification of aptamers that recognize small-molecule, low-epitope targets.…”

Quasi-Two-Dimensional Metal Oxide Semiconductors Based Ultrasensitive Potentiometric Biosensors

“…[40][41][42][43][44][45] Previously, aqueous metal oxide precursor solutions [46][47][48][49][50][51][52] were used successfully to fabricate high-quality oxide semiconductors with field-effect mobility as high as 36.31 cm 2 V -1 s -1 , 46 to fabricate conformal bioelectronics for wearable health-monitoring platforms, 53 and for sub-nanomolar neurotransmitter detection. 54 Yet, to date, there have been limited systematic studies of oxide semiconductor-based Bio-FETs that addressed the fundamental factors of how the devices' parameters affect their sensitivity or any, detailed electrical characterization to estimate the lowest detectable charge.…”

Low-Impurity High-Performance Solution-Processed Metal Oxide Semiconductors via a Facile Redox Reaction

“…Low thermal budget processes provide external energy such as ultraviolet irradiation, [8][9] microwave annealing, 10 infrared exposure, 11 and high-pressure annealing to reduce the thermal budget. [12][13][14] In the new chemical approaches, ligands and counter ions are carefully designed to reduce the activation energy and lower the thermal budget, as in alkoxide systems, 15 combustible processes, 8,[16][17] and aqueous routes [18][19][20][21] . Among these methods, the carbon-free aqueous route can form high-quality films at low temperatures with minimal environmental impact.…”