Journal
NANO LETTERS
Volume 14, Issue 5, Pages 2394-2400Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nl500042x
Keywords
Vanadium dioxide; thermoreflectance microscopy; Peltier effect; Joule heating; metal-insulator domain wall
Categories
Funding
- US Department of Energy [DE-FG02-11ER46796]
- National Science Foundation [DMR-0820404, DMR-1006541, DMR-1210588]
- Center for Energy Efficient Materials, an Energy Frontier Research Center - U.S. Department of Energy, Office of Basic Energy Sciences [DE-SC0001009]
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [1006541] Funding Source: National Science Foundation
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The metal to insulator transition (MIT) of strongly correlated materials is subject to strong lattice coupling, which brings about the unique one-dimensional alignment of metal insulator (M-I) domains along nanowires or nanobeams. Many studies have investigated the effects of stress on the MIT and hence the phase boundary, but few have directly examined the temperature profile across the metal insulating interface. Here, we use thermoreflectance microscopy to create two-dimensional temperature maps of single-crystalline VO2 nanobeams under external bias in the phase coexisting regime. We directly observe highly localized alternating Peltier heating and cooling as well as Joule heating concentrated at the M I domain boundaries, indicating the significance of the domain walls and band offsets. Utilizing the thermoreflectance technique, we are able to elucidate strain accumulation along the nanobeam and distinguish between two insulating phases of VO2 through detection of the opposite polarity of their respective thermoreflectance coefficients. Microelasticity theory was employed to predict favorable domain wall configurations, confirming the monoclinic phase identification.
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