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In this work, an analytical model is developed for DM-DG-TMD-FET- based Biosensor including Fringing-field effects. The Analytical model has been developed for two different Device structures, namely Device structure-1 (without a gate above the nano-cavity) and Device structure-2 (with a gate above the nano-cavity) based on modulation of the dielectric constant of biomolecules in the nano-cavity region. The proposed model has been validated against both numerical quantum simulation results with the help of a few fitting parameters and it also agrees with the 2-dimensional numeric simulator SILVACO TCAD used in this work. The presence/absence of biomolecules has been detected by the metric of threshold voltage sensitivity $$S_{Vth}$$ S Vth and drain current $$I_{d}$$ I d for the neutral as well as charged biomolecules. Sensitivities of partially filled nano-cavities arising out of steric hindrance in both the biosensors are compared. Optimization of device dimensions has also been included in this work to enhance the sensitivity of the biosensors. It has been witnessed that the sensitivity of the proposed biosensor is $$\sim$$ ∼ 100% higher in Device structure-1 for neutral biomolecules with dielectric constant $$\kappa$$ κ  = 12, when compared to Device structure-2 for fully filled cavities. Whereas for the charged biomolecules, Device structure-1 shows $$\sim$$ ∼ 50% enhanced sensitivity than Device structure-2 for $$N_{f}=-1\times 10^{-12}$$ N f = - 1 × 10 - 12 $$\text{C}/\text{cm}^2$$ C / cm 2 . Device structure-1 demonstrates $$\sim$$ ∼ 120% higher sensitivity than Device structure-2 with partially filled cavities (i.e. 66% filled cavity). Finally, benchmarking of the proposed biosensor is presented with contemporary, state-of-the-art biosensors and it is highlighted that $$MoS_{2}$$ M o S 2 FET-based biosensor emerges with a superior sensitivity of $$S_{Vth}$$ S Vth  = 0.81 V for $$\kappa = 12$$ κ = 12 .

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Abstract. Instruments with single-molecule level detection capabilities can potentially benefit a wide variety of fields, including medical diagnostics. However, the size, cost, and complexity of such devices have prevented their widespread use outside sophisticated research laboratories. Fiber-only devices have recently been suggested as smaller and simpler alternatives, but thus far, they have lacked the resolution and sensitivity of a full-fledged system, and accurate alignment remains a critical requirement. Here we show that through-space reciprocal optical coupling between a fiber and a microscope objective, combined with wavelength division multiplexing in optical fibers, allows a drastic reduction of the size and complexity of such an instrument while retaining its resolution. We demonstrate a 4×4×18 cm 3 sized fluorescence correlation spectrometer, which requires no alignment, can analyze kinetics at the single-molecule level, and has an optical resolution similar to that of much larger microscope based devices. The sensitivity can also be similar in principle, though in practice it is limited by the large background fluorescence of the commonly available optical fibers. We propose this as a portable and field deployable single molecule device with practical diagnostic applications. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).