High-quality crystallinity controlled ALD TiO2 for waveguiding applications

Tapani Alasaarela, Lasse Karvonen, Henri Jussila, Antti Säynätjoki, Soroush Mehravar, Robert A. Norwood, Nasser Peyghambarian, Khanh Kieu, Ilkka Tittonen, Harri Lipsanen

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


We demonstrate a novel atomic layer deposition (ALD) process to make high-quality nanocrystalline titanium dioxide (TiO2) with intermediate Al2O3 layers to limit the crystal size. The process is based on titanium chloride (TiCl4) + 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 TiO2 deposited at 250°C without the intermediate Al2O3 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 TiO2 is an excellent candidate for various optical applications, where good thermal stability and high third-order optical nonlinearity are needed.

Original languageEnglish (US)
Pages (from-to)3980-3983
Number of pages4
JournalOptics letters
Issue number20
StatePublished - Oct 15 2013

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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