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(a) Tilted image of the fabricated biristor taken from a scanning electron microscope (SEM). (b) Measured I-V characteristics of the biristor. The electrical state abruptly transited from a high resistance state to a low resistance state via impact ionization. (c) Schematic of the proposed biosensor with immobilized biomolecules on the surface of the SiNW. (d) Energy band diagram of the biristor. The charged biomolecules on the SiNW alter the potential of the floating-body according to the charge polarity.
Flow of fabrication process from (a) to (d) for the biristor, and (e) cross-sectional SEM images of the SiNW with different isotropic etching times. The suspended SiNW on a bulk Si substrate is fabricated by the one-step etching route known as the Bosch process. For the formation of the n+-p-n+ junctions, the center of the p-type SiNW is passivated by PR during the implantation of n-type dopants.
(a) Effects of charge on VT rig shift. The electrical characteristics of the biristor are significantly changed by both negative and positive charged polymers. (b) Each peak point, which is accurately obtained from the derivative of I with respect to V, is defined as VT rig .
(a) Measured I-V characteristics of the biristor with bio-experiments. SBP-AIa with 25 μg/ml (86.7 nM) is first immobilized; then, anti-AI at 10 μg/ml (66.8 nM) is specifically bound with AIa. After anti-AI binding, VT rig increases from 3.5 V to 5.5 V due to the negative charge polarity. The slope in the inset stands for the detection sensitivity of the proposed device. (b) Summarized experimental results of specific and non-specific bindings. The concentration of anti-rabbit IgG is also 10 μg/ml (66.8 nM). Notable shift of VT rig is only observed in the case of a specific antigen-antibody reaction. The error bar is the standard deviation of 12 devices.
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