Microstructure, optical properties, and optical resonators of Hf_1-xTi_xO_2 amorphous thin films

Abstract

We report Hf 1-x Ti x O 2 (0< = x< = 1) thin films (HTO) as index tunable and highly transparent materials for ultraviolet to near infrared integrated photonic devices. By varying the Ti concentration, reactive cosputtered HTO thin films on thermal oxidized SiO 2 on Si substrates show continuously tunable optical band gaps from 3.9 eV to larger than 5 eV. The film refractive index monotonically increases with Ti concentration, varying from 1.8 to 2.4 in the visible to near infrared wavelength range. Micro-disk amorphous HfO 2 resonators on SiO 2 /Si substrates are fabricated using sputtering and lift-off method. A loaded quality factor of ~15800 at around 1580 nm wavelength is achieved in HfO 2 disk resonators with diameters of 100 μm. The propagation loss of the HfO 2 ridge waveguide is estimated to be 2.5 cm −1. The wide optical transparency range, variable index of refraction, low temperature, CMOS-compatible fabrication capability, and high optical transparency make amorphous HTO thin films promising candicates for integrated photonic applications.

Influence of Substrates on Structure Development and Concentration of Residual Impurities in Hafnium–Titanium-Oxide Films Grown by Atomic Layer Deposition

“…This work focused on Hf x Ti 1– x O y films because of potential applications ranging from different electronic devices − to optical and scintillator materials. As in a number of cases, ALD has been used for the deposition of Hf x Ti 1– x O y films; ,,, these films as well as the ALD methods usable for the deposition of those are of significant practical interest.…”

“…The intention was to better understand how general could be the result that the contamination of films with precursor ligands tends to be lower in the crystalline films than that in the amorphous films obtained on different substrates at the same ALD process parameters. This work focused on Hf x Ti 1−x O y films because of potential applications ranging from different electronic devices 9−13 to optical 14 and scintillator 15 materials. As in a number of cases, ALD has been used for the deposition of Hf x Ti 1−x O y films; 9,10,12,13 these films as well as the ALD methods usable for the deposition of those are of significant practical interest.…”