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In this article, the authors show that geometric asymmetry in the layout of tunnel diodes yields asymmetry in the current-voltage ͑I-V͒ relationships associated with these diodes. Asymmetry improves diode performance. This effect is demonstrated for polysilicon-SiO 2-Ti/ Au and for Ni-NiO-Ni tunneling structures. For a polysilicon-SiO 2-Ti/ Au asymmetric tunneling diode ͑ATD͒, sensitivity and I-V curvature improvements of 71% and 350% are achieved, respectively. For a Ni-NiO-Ni asymmetric diode, sensitivity and I-V curvature improvements of 15% and 39% are observed. The authors further demonstrate that this asymmetry enhances the microwave radiation detection sensitivity of these diodes at 900 MHz. Superior rectifying performance of a Ni ATD is observed due to smaller band-edge offsets in this material compared to that of a polysilicon ATD. The resulting structure can be further optimized using plasmonic field enhancement.

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A carbohydrate-based biosensor was prepared by functionalization of the surface of an etched fiber Bragg grating with a glucopyranosyl-siloxane conjugate. Functionalization of the surface with the conjugate resulted in a Bragg grating shift of 24 pm. This shift in the refractive index is consistent with a theoretical shift calculated assuming monolayer coverage of the glucose conjugate on the sensor. The resulting functionalized fiber was shown to interact selectively with concanavalin A (Con A), a glucose binding protein (lectin). Exposure of the glucose-functionalized fiber to peanut agglutinin, a galactosebinding lectin, did not result in a change of the refractive index corresponding to a binding event.

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