title: High-quality crystallinity controlled ALD TiO2 for waveguiding applications.
abstract: We demonstrate a novel atomic layer deposition (ALD) process to make high-quality nanocrystalline titanium dioxide (TiO(2)) with intermediate Al(2)O(3) layers to limit the crystal size. The process is based on titanium chloride (TiCl(4))+water and trimethyl aluminum (TMA)+ozone processes at 250°C deposition temperature. The waveguide losses measured using a prism coupling method for 633 and 1551 nm wavelengths are as low as 0.2±0.1 dB/mm with the smallest crystal size, with losses increasing with crystal size. In comparison, plain TiO(2) deposited at 250°C without the intermediate Al(2)O(3) layers shows high scattering losses and is not viable as waveguide material. The third-order optical nonlinearity decreases with smaller crystal size as verified by third-harmonic generation microscopy but still remains high for all samples. Crystallinity controlled ALD-grown TiO(2) is an excellent candidate for various optical applications, where good thermal stability and high third-order optical nonlinearity are needed.
authors: Tapani
authors: T
authors: Alasaarela
authors: Lasse
authors: L
authors: Karvonen
authors: Henri
authors: H
authors: Jussila
authors: Antti
authors: A
authors: Säynätjoki
authors: Soroush
authors: S
authors: Mehravar
authors: Robert A
authors: RA
authors: Norwood
authors: Nasser
authors: N
authors: Peyghambarian
authors: Khanh
authors: K
authors: Kieu
authors: Ilkka
authors: I
authors: Tittonen
authors: Harri
authors: H
authors: Lipsanen