| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1786688 | Current Applied Physics | 2013 | 5 Pages |
This work involves the study of the positive emittance-switching (i.e. emittance that increases with increasing the temperature) of thermochromic VO2 films deposited using reactive pulsed laser deposition (RPLD) on Al substrates. The temperature dependence of the emittance of a 260 nm-thick VO2 film on Al substrate revealed a maximum of the emittance of 0.29 around 68 °C. It is attributed to an increase in the infrared radiation absorption by the VO2 film due to the coexistence of both insulating and metallic phases in the vicinity of the transition temperature of VO2. The emittance tunability between 25 °C and 68 °C is 0.21. Since practical SRD application requires both high emittance at high temperature and large tunability, we demonstrate, by both simulation and fabrication, that these goals can be accomplished to some extent by a top dielectric a-Si:H/SiO2λ/4 stack layer. In fact, the addition of a-Si:H/SiO2λ/4 overlayer results in an increase of the maximum value of the emittance by 114% (from 0.29 to 0.62) as well as an increase of the tunability by 81% (from 0.21 to 0.38). This work reports an important improvement of the positive emittance-switching efficiency of the VO2-based structures and holds promise for a new generation of smart radiator devices (SRDs) for a passive thermal control of spacecrafts.
► Emittance of VO2/Al vs. temperature shows a positive switch with a maximum at 68 °C. ► a-Si:H/SiO2λ/4 overlayer improves the VO2/Al emittance switch vs. temperature. ► The highest emittance at high temperature reported so far for a VO2-based system. ► The largest tunability of the emittance reported so far for a VO2-based system. ► The system holds a strong potential as a passive smart radiator device (SRD).
