| 1. |
- Conache, Gabriela, 1977-, et al.
(författare)
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Nanowire friction with an applied bias
- 2009
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Konferensbidrag (refereegranskat)abstract
- Recently, we have shown how the friction acting on nanowires pushed across a surface by an AFM tip can be determined by measuring the radius of curvature of the bent wire aŸer manipulation. This technique allows us to study the friction properties of an extended mesoscale contact. Our main focus has been to determine whether such contacts behave like macroscopic objects, in which dišerences between the 'true' and 'apparent' contact areas play a key role and friction varies linearly with the applied normal force, or whether they are more like atomic-scale point contacts, wheremore fundamental processes dominate and friction oŸen is independent of the normal force. In this work we show how the friction between InAs nanowires and an insulating silicon nitride layer on a conductive silicon substrate varies when a DC voltage is applied to the AFM tip during manipulation. e tip charges the capacitor formed by the wire and the grounded silicon back contact, giving rise to attractive Coulomb forces and thus increasing the contact pressure between the wire and the silicon nitride. In this way we can vary the normal force on the sliding surfaces using a single wire, with a constant structure and contact geometry. Using nanowires of about 40-50 nm diameter and a few microns in length we have applied tip voltages in the range +12 to -12 V. Simplemodeling indicates that these voltages su›ce to give similar levels of band-lling and depletion to when the same wires are used in working wrap-gate or back-gate devices. A monotonic increase of the sliding friction with the voltage applied on the tip was observed. is implies that the friction increases with the normal force and that this mesoscopic system behaves more like a macroscopic contact, despite the nanometer size of the contact in the direction of motion.
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| 2. |
- Pettersson, Håkan, et al.
(författare)
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Friction measurements on InAs NWs by AFM manipulation
- 2008
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Konferensbidrag (refereegranskat)abstract
- We discuss a new approach to measure the friction force between elastically deformed nanowires and a surface. The wires are bent, using an AFM, into an equilibrium shape determined by elastic restoring forces within the wire and friction between the wire and the surface. From measurements of the radius of curvature of the bent wires, elasticity theory allows the friction force per unit length to be calculated. We have studied friction properties of InAs nanowires deposited on SiO2, silanized SiO2 and Si3N4 substrates. The wires were typically from 0.5 to a few microns long, with diameters varying between 20 and 80 nm. Manipulation is done in a `Retrace Lift' mode, where feedback is turned off for the reverse scan and the tip follows a nominal path. The effective manipulation force during the reverse scan can be changed by varying an offset in the height of the tip over the surface. We will report on interesting static- and sliding friction experiments with nanowires on the different substrates, including how the friction force per unit length varies with the diameter of the wires.
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