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NWScan Report Summary

Project ID: 334762
Funded under: FP7-IDEAS-ERC
Country: Switzerland

Mid-Term Report Summary - NWSCAN (Bottom-up Nanowires as Scanning Multifunctional Sensors)

We have been studying the use of nanowires (NWs) as sensitive scanning sensors, by introducing two new scanning probe techniques.

First, we use an individual as-grown NW to realize the vectorial scanning force microscopy of a patterned surface. By monitoring the NW’s first-order flexural mode doublet, we fully determine the magnitude and direction of the static tip-sample force derivatives in the 2D scanning plane. Our measurements demonstrate the potential of NWs as sensitive scanning vectorial force sensors. The technique is generally applicable and could, for instance, be used to measure magnetic forces with proper functionalization of the NW tip or even in liquid for the study of batteries, water splitting, or fuel cells. Our method may eventually be capable of atomic-scale or even sub-atomic-scale force microscopy with directional sensitivity. In this way, one could imagine the use of vectorial NW-based AFM of tip-sample forces and non-contact friction to reveal, for example, the anisotropy of atomic bonding forces.

Second, we realize a fiber-coupled quantum dot (QD) on a photonic tip. The photonic tip is a conical GaAs NW designed to with an embedded QD designed to efficiently channel light to the core of the optical fiber, to which it is attached. The entire device is then used as a scanning probe. In particular we use the QD at the apex of the NW as an ultra-sensitive electric field sensor, through its Stark shift. Based on theoretical predictions, the sensor could be as sensitive as the best single electron transistors, which have been demonstrated. We have recently demonstrated a working fiber-coupled QD and are now testing its capabilities as a scanning probe.

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