Atomic layer deposition of SnTiOx for photonics applications

Groep: CoCooN

Promotor:Stéphane Clemmen, Christophe Detavernier

Begeleiding: Jolien Dendooven, Artur Hermans, Michiel Van Daele

Inlichtingen: tel. 09/264.43.42 of contacteer rechtstreeks een betrokken persoon (de contact-gegevens opvragen door op de naam te klikken)

Crystalline materials lacking inversion symmetry can exhibit second-order nonlinear optical response. Second-order nonlinear optical effects are at the heart of many applications such as coherent light generation in optical parametric oscillators and light modulation in electro-optic modulators. An important challenge, however, is the integration of these applications on nanophotonic chips in a way that is compatible with the standard CMOS processing technology in microelectronics. Since the 2 most prominent photonic platforms (silicon and silicon nitride) lack second-order nonlinearity, thin films overlays of suitable materials are a desirable way to introduce this lacking property. This can be achieved via atomic layer deposition (ALD): a low-temperature thin-film deposition method that provides thickness precision at the sub-nanometer level and yields highly uniform layers over a large variety of substrates. This master thesis project aims to explore tin titanate (SnTiOx) thin films grown by ALD as candidate for the introduction of second-order nonlinear optical response in silicon-based nanophotonic platforms.

This master thesis project is primarily experimental. A first goal will be the synthesis of amorphous tin titanate thin films by ALD. This will require optimization of the deposition conditions based on thickness and composition characterizations of the deposited layers by spectroscopic ellipsometry, X-ray reflectivity, X-ray fluorescence and X-ray photoelectron spectroscopy. Secondly, the ALD-grown thin films need to be crystallized by heating the samples in a controlled atmosphere. To speed up screening of the annealing conditions, the temperature treatments will be performed in a dedicated setup that is positioned in an instrument for X-ray diffraction measurements. This will allow monitoring the diffraction pattern during heating of the sample. Thirdly, the second-order nonlinear optical response of the crystalline tin titanate layers will be studied as a function of the composition and crystallinity via SHG (second harmonic generation) experiments. If a material with a large enough second order nonlinearity is found, it will be deposited onto existing silicon nitride waveguides so that its electro-optic effect can be studied. As such, this master thesis project will result in extensive know-how and hands-on experience with thin film deposition and characterization methods as well as with optical material characterization and integration.