Fabrication and performances of double-sided HfO2 anti-reflection films with ultra-high infrared transmittance

Si is one of the most important infrared optical materials. However, the high refraction index of Si in the infrared regions leads to large reflection losses, so increasing the infrared transmittance is of great significance to practical application. HfO2 film is widely investigated due to the high-k gate dielectric properties. And it also has excellent optical properties to be used as anti-reflection film for Si. In this study, doubled-sided HfO2 films (HfO2/Si/HfO2) were fabricated as anti-reflection coating on Si substrate to further enhance the infrared transmittance (99%). And the transmittance peak can be regulated by adjusting the thickness of HfO2 film. Besides, the deposition temperature had been optimized by using XRD, XPS, SEM, AFM, and optical measurements. The results indicate good crystallinity and flat surface for the samples. Furthermore, HfO2 films show surface hydrophobic properties, which can prevent water in the infrared application. These encouraging results show the HfO2 films have excellent application prospective for the infrared optical systems. [Display omitted] •The ultrahigh infrared transmittance (99% at 6.6 µm) of double-sided HfO2 film was obtained.•Hafnium oxide film (HfO2) can not only reduce reflection of the Si substrate, but also possess good hydrophobicity.•The HfO2 films have been prepared using a reactive DCMS method.