Employing Ion-Beam Sputter Deposited TiO2 Buffer Layers for VO2-Related Devices

Vanadium dioxide (VO2) is considered to bethe mostpromising material for thermochromic smart windows due to its insulator-to-metaltransition causing an abrupt change of transmittance near ambienttemperature. TiO2 buffer layers are expected to have abeneficial impact on the growth and performance of the functionalVO(2) thin film, as they may induce crystallinity at lowergrowth temperatures and act as a barrier layer for ion diffusion fromglass substrates. However, a systematic evaluation of TiO2 buffer layers of different phases and thicknesses to assess potentiallycompeting impacts is still lacking. Here, we grow TiO2 bufferlayers by ion-beam sputter deposition (IBSD) at different substratetemperatures to obtain amorphous TiO2 as well as crystallineTiO(2) in the anatase and rutile phase, respectively. Weinvestigate the buffer layers themselves and shed light on how thesebuffer layers influence the performance of the functional VO2 layer grown on top by combining experimental and theoretical means.We find that the VO2||TiO2 interface is themost crucial part of the multilayer structure with an urgent needfor minimum roughness. The two types of crystalline TiO2 buffers yield similar results in terms of optical performance; however,we find that only rutile buffer layers significantly relieve the growthconditions needed.

Automated summary

Vanadium dioxide (VO2) is the most promising material for thermochromic smart windows due to its insulator-to-metal transition causing an abrupt change of transmittance near ambient temperature. TiO2 buffer layers are beneficial for the growth and performance of VO2 thin film. The growth conditions of VO2||TiO2 interface are crucial, and only rutile buffer layers significantly relieve the growth conditions needed.