Wednesday  |  Conference Center A  |  03:10 PM–03:30 PM

#13412, Tensile Testing of individual Vanadium Dioxide Nanowires

We investigate Vanadium Dioxide (VO2) nanowires (NW), a material which, due to its strain and temperature driven phase changes, is interesting for the implementation of strain and temperature-controlled switches, actuators, and sensors. Although the temperature-driven phase changes of these nanowires have been studied extensively, much less is known about the nature of the strain-driven ones. To overcome this issue, we carry out comprehensive testing of VO2 nanowires for several diameters and lengths.

VO2 NWs are deposited in Silicon (Si) substrates by self-assembly and microfluidic patterning methods, in order to align them in one direction. Then, the Si substrates are broken such that some portion of the aligned NWs remain outside of the substrate,. These aligned nanowires are then strained along the axial NW direction to measure their stress-strain curves using nanomechanical testing. First, the NWs are taken under the optical microscope; then, a tip from an AFM cantilever probe is brought near the NWs by using a nanomanipulator device. UV curing glue is used to weld the tip and the nanowire. After this, the nanowire is strained by pulling the AFM cantilever in the opposite direction. Once testing of one NW is finished, we move to the next NW and repeat the technique. As such, this technique allows to increase the efficiency of nanowire testing. The results are analyzed by measuring the force measured with the cantilever and the images captured by the microscope.

The results show that the nanowires display a plateau in the stress-strain curve upon phase transformation, reminiscent of for example, the transformation of liquid to vapor in water. We quantify this plateau for several nanowires in order to characterize the entropy change associated to this phase transformation. The entropy changes are then used to estimate the potential temperature changes that can be achieved by stretching these nanowires.

Al-Mustasin Hossain   University of Texas at Dallas
Rodrigo Bernal   University of Texas at Dallas