Invited
Functional nanowire hybrids for device applications; Electronic sensors and plasmonic-enhanced near-infrared detectors using nano-florets

Programmable introduction of heterogeneity at the nanoscale plays a key role in the design of functional building blocks for catalysis, electronic devices, and numerous other applications. Synthetic strategies for attaining well-defined heterogeneity in structure, shape, composition, and modulation of the electronic structure at selected regions of the nano system is therefore highly desired.

Recently we introduced the synthesis of a new class of hybrid nano structures termed `nano-florets` featuring a semiconducting nanowire decorated with a metallic tip. Here, the application of these functional nanowire hybrids for device applications will be discussed.

Standard optical lithography is utilized for connecting the nano-floret nano junctions to macroscopic electrodes resulting in operable devices with the key functional element of the device delivering molecular-level information. In addition, the devices are operable under atmospheric pressure and even at liquids with no need for vacuum while delivering molecular-level electronic information.

For example, introduction of quantum dots results in the mapping of their band structure under ambient conditions. The metallic tip of the hybrid nanostructures show plasmonic absorption extending from the VIS to the NIR and up to the short wave infrared (SWIR) spectral ranges. we present device concept for NIR-SWIR detection using these hybrid nanostructures. Plasmonic gain of three orders of magnitude is obtained with improved time response compared to nanowire-based detector due to the metal-semiconductor Schottky junction. Our results provide a proof-of-concept of large scale self-forming nanogap device platform realized using simple fabrication tools. Such a systems can be used for sensing, as a potential building block for molecular electronics, and as a platform for studying the molecular-level electronic details of complex systems under ambient conditions.

Figure 1. Nano-floret structures (a) obtained for SiGe nanowires reacted with Cu, Ag. (b) Typical dimensions of the Nano-floret components; overall length of 1-100 microns resulting from the SiGe NW used, deposited metal cap is typically 10-100nm in diameter and 50-500 nm long. (c) Opto-electric Nanogap sensor featuring Nano-floret nano systems