Abstracts Book - IMRC 2018

• SA6-O032
THERMAL HYSTERESIS MEASUREMENT OF THE VO2 EMISSIVITY
AND ITS APPLICATION IN THERMAL RECTIFICATION
Cindy Lorena Gomez Heredia 1 , Jorge Andres Ramirez Rincon 1 , Jose Ordonez Miranda 2 , Oscar
Ares Muzio 1 , Juan José Alvarado Gil 1 , Corinne Champeaux 3 , Frederic Dumas Bouchiat 3 , Younes
Ezzahri 4 , Karl Joulain 4
1 Centro de Investigación y de Estudios Avanzados del IPN - CINVESTAV, Física Aplicada, Mexico.
2 CNRS, Institut Pprime, Institut PPRIME, France. 3 CNRS, IRCER, France. 4 CNRS, Institut Pprime,
Université de Poitiers, France.
Principal and secondary hysteresis loops in the emissivity of VO2 thin films (120
nm and 300nm) grown on sapphire and silicon substrates by a pulsed laser
deposition process are experimentally measured through the thermal-wave
resonant cavity technique. Remarkable variations of about 43% are observed in
the emissivity of both VO2 films, within their insulator-to-metal (heating) and
metal-to-insulator (cooling) transitions. It is shown that: i) The principal
hysteresis width (maximum slope) in the VO2 emissivity of the VO2+silicon
sample is around 3 times higher (lower) than the corresponding ones of the
VO2+sapphire sample. The presence of the substrate (silicon or sapphire)
induces significant differences on the VO2 film microstructures and the resulting
metal-insulator transitions (MITs). A wider principal hysteresis loops with slower
MIT is obtained in VO2 grown on silicon compared, to the film deposited on
sapphire. ii) Secondary hysteresis loops, obtained by interrupting the heating
process of both samples within the MITs, fall within the principal ones, such that
their width and maximum slopes decrease as the temperature of this
interruption reduces. The hysteresis width and the rate of change of the VO2
emissivity in a VO2+substrate sample can therefore be tuned with its secondary
hysteresis loop. iii) VO2 samples can be used to build up a radiative thermal
diode, which is able to operate with a theoretical rectification factor as high as
83%, when the temperature difference of its two terminals is around 17 °C. This
record-breaking rectification constitutes the highest one reported in the
literature, for a relatively small temperature change of the diode terminals.
Keywords: Vanadium dioxide, emissivity, thermal diode
Presenting authors email: cindy.gomez@cinvestav.mx