Simultaneous realization of infrared-light switching and high visible-light transmittance in extremely thin VO2 films grown on ZnO-nanorods buffered glasses

The authors demonstrate a significant effect of ZnO-nanorod buffer layers on the growth of extremely thin VO2 films. Highly c-axis oriented ZnO-nanorods were grown on glasses with sputtered ZnO-seed layers by using the chemical bath deposition method. Introducing an organic compound, (CN2)(6)N-4 (hexamethylenetetramine), together with a Zn source, Zn(NO3)(2), achieved highly c-axis oriented ZnO-nanorods with an average diameter of around 150nm. Due to such a superior template, b-axis oriented VO2 films were grown on the ZnO-nanorod buffered glasses even with the film thickness lower than several tens of nanometers. The thinnest VO2 film emerged in insulator-metal transition, achieving high visible-light transmittance and clear infrared-light switching, which are characterized by luminous transmittance (T-lum) of 56% even at metallic state and solar modulation ability (Delta T-sol) of 6.0%. The results obtained in this study propose a way to achieve practical smart windows that enable not only infrared-light switching but also maintaining high visible-light transmittance without any optical design.