Tuning the pH Response of Monolayer Hexagonal Boron Nitride/Graphene Field-Effect Transistors
Research Square (Research Square)(2023)
摘要
Abstract Scaling the fabrication of 2D devices for pH sensing will have implications in materials and life sciences. Monolayer hexagonal boron nitride has recently reached commercial wafer-scale transferability on monolayer graphene and is hypothesized to preserve graphene quality, reducing device-to-device variation, while simultaneously screening charge density at the liquid-solid interface resulting in attenuation of pH sensitivity of the graphene transducer. The pH-dependencies of field-effect transistors derived from monolayer hexagonal boron nitride/graphene were compared to monolayer graphene on four-inch SiO2/p-type Si wafers. Photoresistless fabrication of the two-dimensional devices relied on shadow masking for metallization, and the sensing areas were defined using microcentrifuge tube masking and reactive ion etching to produce quasi-pure sensing areas. Microcentrifuge tubes sealed the devices and were opened for experimentation where the liquid-gated Dirac voltages were studied as a function of pH in 10 mM phosphate solutions. The sensitivity of the shift in the Dirac voltage versus pH of hexagonal boron nitride/graphene devices (-40 mV/pH) was smaller than bare graphene (-47 mV/pH) with greatest attenuation in the acidic regime. Moreover, triplicating this experiment revealed smaller standard deviations for the hexagonal boron nitride/graphene transistors. Then, electron beam and atomic layer deposition of AlxOy nanofilms were employed before encapsulation to study the tunability of the pH response of hexagonal boron nitride/graphene and revealed thickness-dependent enhancement, with the greatest sensitivity on 8.6 nm AlxOy/hBN/graphene/SiO2 (-100 mV/pH). Then, reversion of the pH response upon dissolving the AlxOy was characterized. In this work, nanoscale dielectrics enabled tuning of the electrical response of graphene-based pH sensors.
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关键词
monolayer hexagonal boron nitride/graphene,field-effect
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