Paper Title
GATE-LENGTH SCALING AND LANGMUIR ADSORPTION MODELING OF BACK-GATED GRAPHENE FET GLUCOSE SENSORS

Abstract
This study investigates the gate-length dependence of unmodified back-gated graphene field-effect transistors (GFETs) for glucose sensing applications. Graphene’s high carrier mobility, large surface-to-volume ratio, and biocompatibility make it a promising channel material for biosensors, yet systematic studies on the scaling behavior of GFETs remain limited. In this work, GFET devices with varying gate lengths (from 2 µm to 20 µm) were fabricated on Si/SiO₂ substrates and characterized through electrical measurements under controlled glucose concentrations. Dirac point shifts (ΔV_Dirac) were extracted and analyzed using the Langmuir adsorption model to determine adsorption constants (K) and maximum coverage (θ_max). The results reveal a clear gate-length dependence, with shorter channels exhibiting higher sensitivity due to stronger electrostatic modulation, while longer channels showed higher adsorption constants, reflecting more stable adsorption kinetics. The high R² values (>0.95) confirm the validity of Langmuir adsorption in describing glucose–graphene interactions. These findings highlight the trade-off between sensitivity and stability, suggesting that device miniaturization enhances detection limits, while longer channels favor stability and reproducibility. Overall, this work provides new insights into gate-length scaling in GFET biosensors and establishes a framework for optimizing device architectures for future biomedical sensing applications. Keywords - Graphene FET; Glucose Sensor; Gate-Length Scaling; Langmuir Adsorption; Biosensors; Nanomaterials