Intrinsic Properties and Future Perspective of HfO2/V2O5/HfO2 Multi-Layer Thin Films via E-Beam Evaporation as a Transparent Heat Mirror

HfO2 and V2O5 as multi-layer thin films are discussed for their potential use as transparent heat mirrors. Multi-layered HfO2/V2O5/HfO2 thin films with a thickness of 100/60/100 nm were prepared via e-beam evaporation on a soda-lime glass substrate. Rutherford backscattering confirmed the multi-layer structure with uniform surface. The as-deposited thin films were annealed at 300 degrees C and 400 degrees C, respectively, for 1 h in air. The transmittance of approximately 90% was obtained for all thin films. Due to the relatively low thickness and non-stoichiometry of HfO2, a band gap of approximately 3.25 eV was determined (instead of the theoretical 5.3-5.7 eV). The as-deposited thin films possessed conductivity of approximately 0.2 ohm(-1)cm(-1) and increased to 1 ohm(-1)cm(-1) and 2 ohm(-1)cm(-1) for thin films annealed at 300 and 400 degrees C, respectively. Due to the unique intrinsic properties of HfO2/V2O5/HfO2 thin films, the results obtained are promising for application as a transparent heat mirror.