Nanocomposites by hybrid process coupling PECVD and chemistry in solution

Marie-Paule Besland, Antoine Goullet, Agnès Granier, Mireille Richard-Plouet, PhD Students :  Sarah Hekking |2023-2026], Simon Chouteau [2020-2023], Julien Chevet [2021-2024] 

PhDs : Maria Mitronika (2020)

The synergy between the Soft Chemistry and PECVD skills (link to the Thin Film PECVD sub-topic) has made it possible to develop and optimise an innovative hybrid process: consisting of injecting a colloidal solution into a low-pressure plasma. The use of low pressure plasma allows, compared to the approaches developed at atmospheric pressure, a better control and modulation of the energy transfer to the active species (radicals and ions) of the plasma. On the other hand, our specificity consists in using colloidal solutions of nanoparticles, NPs, (link to the sub-theme Chemical deposition of transition metal oxides in Thin Films) prepared in the laboratory, stable in selected organic solvents, to produce nanocomposite thin films (NCs) formed of NPs dispersed in a matrix.
These materials with tunable optical index and dielectric constant are good candidates for the development of optical and electrical Integrated Passive Devices.

Keywords :           Physics of low-pressure plasma, PECVD process and coupling with chemistry in solution, Plasmas diagnostics, Plasma-Surface interactions
Collaborations     LAPLACE (Toulouse), Université de Montréal (Canada), CEITEC (République tchèque)
Expertises            PECVD, Chemistry in solution,  Ellipsometry

To go further 
Nanocomposite by hybrid process       Effect of plasma treatment on TiO₂ NPs             Local electrical measurements

 Our objective was to optimize the hybrid process coupling PECVD and pulsed injection of colloidal solutions in order to synthesize NCs nanocomposite thin films of TiO₂ nanoparticles in a SiO₂ matrix, noted TiO₂@matrix SiO₂, with tunable optical and dielectric properties (thesis M. Mitronika, collaboration UdeM and LAPLACE). The plasma used is an ICP (inductively coupled plasma) radio-frequency plasma created at low pressure. Our approach includes the injection of the solvent alone, of the solution with the nanoparticles (NPs) (i) without plasma, (ii) in an oxygen plasma, (iii) in an O₂/hexamethyldisiloxane plasma (HMDSO), with implementation of plasma diagnostics (OES) and spectroscopic ellipsometry in situ and resolved in time to study the effect of the pulsed injection of the solution on the plasma and the growth of the nanocomposite thin layer.

A parametric study enabled a first level of understanding and therefore control of the process to be acquired. The pulsed injection sequence of the colloidal solution was optimised to ensure the stability of the plasma and control the quantity of NPs injected. The feasibility of the hybrid process is demonstrated with the injection of a colloidal solution of 5 nm TiO₂ crystallised NPs and the dispersion of the NPs in a dense SiO₂ matrix. The structural characterisations have highlighted the homogeneity of the films, in a wide range of TiO₂ content from 1 to 58 vol% deduced from the ellipsometric analysis, which provides information on the optical properties of the NCs (Maria Mitronika et al., 2020).

This original work is part of the continuation of studies on the TiO₂-SiO₂ nanostructured films prepared by PECVD and their characterisation from the optical (Ondracka et al., 2017), structural (Ondračka et al., 2020) points of view, as well as from the local electrical point of view by AFM(M. Mitronika et al., 2020b). The development of the hybrid process also required preliminary studies in order to highlight possible structural modifications of the TiO₂ NPs induced by the plasma treatment. The latter in fact induces a mineralisation of the nanoparticles by oxidation of the shell formed by the solvent molecules adsorbed on their surface (M. Mitronika et al., 2020a).

Schematic description of the hybrid process coupling PECVD and injection of lab-made colloidal solutions and the associated characterization tools.

*Mitronika, Maria, Profili, J., Goullet, A., Gautier, N., Stephant, N., Stafford, L., Granier, A., Richard-Plouet, M., 2020. TiO2-SiO2 Nanocomposite thin films deposited by Direct Liquid Injection of colloidal solution in an O2/HMDSO low-pressure plasma. J. Phys. Appl. Phys. https://doi.org/10.1088/1361-6463/abc84d

*Mitronika, M., Profili, J., Goullet, A., Stafford, L., Granier, A., Richard-Plouet, M., 2020a. Modification of the optical properties and nano-crystallinity of anatase TiO2nanoparticles thin film using low pressure O2 plasma treatment. Thin Solid Films 709, 138212. https://doi.org/10.1016/j.tsf.2020.138212

*Mitronika, M., Villeneuve-Faure, C., Massol, F., Boudou, L., Ravisy, W., Besland, M.P., Goullet, A., Richard-Plouet, M., 2020b. TiO2-SiO2 mixed oxide deposited by low pressure PECVD: Insights on optical and nanoscale electrical properties. Appl. Surf. Sci. 148510. https://doi.org/10.1016/j.apsusc.2020.148510

*Ondracka, P., Holec, D., Necas, D., Kedronova, E., Elisabeth, S., Goullet, A., Zajickova, L., 2017. Optical properties of TixSi1-xO2 solid solutions. Phys. Rev. B 95, 195163. https://doi.org/10.1103/PhysRevB.95.195163

*Ondračka, P., Nečas, D., Carette, M., Elisabeth, S., Holec, D., Granier, A., Goullet, A., Zajíčková, L., Richard-Plouet, M., 2020. Unravelling local environments in mixed TiO2–SiO2 thin films by XPS and ab initio calculations. Appl. Surf. Sci. 510, 145056. https://doi.org/10.1016/j.apsusc.2019.145056