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Growth kinetics in transition-metal ceramic compounds

Javier García Molleja

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Where am I?

Postdoctoral researcher at Institut des Matériaux Jean Rouxel (February 2013-February 2014).Director: Pierre-Yves JouanInstitutions:-Centre National de la Recherche Scientifique-Université de Nantes-Chemie et Interdisciplinarité: Synthèse, Analyse,

Modelisation (CEISAM)

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Institutions

Graduate in Physics by Universidad de Córdoba (Spain, July 2001-July2006).Expertise in plasma physics and numerical simulation.

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Institutions

PhD degree by Universidad Nacional de Rosario (Argentina, June 2007-March 2012).Surface treatment of steels using plasmas with carbon or nitrogen. Characterization and irradiation with high energy beams.

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Institutions

Postdoctoral researcher at Instituto de Física de Rosario (Argentina, May 2012-February 2013).Deposition of ternary compounds on cutting blades and adhesion characterization.

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Workplace

Institut des Matériaux Jean Rouxel. Director: Guy Ouvrard.It is an UMR institution (Centre National de la Recherce Scientifique and Université de Nantes).Six different research laboratories, including Plasma et Couches Minces one. Director: Pierre-Yves Tessier.

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Workplace

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So, what is a plasma?

Almost the 90% of visible matter in the universe is under plasma condition (including stars, stardust, nebulae, lightnings and the most part of our atmosphere!).Historically, the plasma has been considered the fourth state of the matter. Gases with high energy (hot gases) may suffer ionization, so this gas is composed by neutral particles, positive ions and electrons.If this system responds to electromagnetic fields, it is called a plasma.

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So, what is a plasma?

We can use plasma for many things, like treatment of surfaces without using high temperatures.To cover delicate things.Cleaning procedures.Lighting devices.Commercial signals with neon.Or they are used as space engines.Yes, I include our new plasma TVs.

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Magnetron… what?

Yes, magnetrons have magnets and we use them to work easily (not always) with plasmas.Magnetrons confines plasma electrons and provoke a lot of ionizations.These positive ions (argon ions, generally) are attracted to the cathode, place where there is a target made of a material of interest (aluminum, chromium, nickel…).The material is sputtered and these particles travel until they reach a substrate, thus they deposit on it.If the plasma contains reactive gases (nitrogen, oxygen…), not only noble ones, is probable a reaction, making a new compound.

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Ok, a sketch of this magnetron sputtering process

This process is stable with different power supplies.We can play with this.Working pressure is very low: less than 100000 times the atmospheric pressure.We need special pumps and avoid the entrance of contaminants.

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Chromium nitride

Film deposition is analyzed under different nitrogen concentrations in our plasma, different working pressure, and different magnetron-substrate distance.Let’s complicate a bit more this stuff: what happens if the power of the discharge is changed?

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Chromium nitride

Different working pressure is relevant under high nitrogen percentages.This huge quantity of nitrogen provokes crystal distortion. Stresses are developed.High power discharge augments the chromium percentage and reduces oxygen and carbon contamination.Possible new surface compounds.It is demonstrated that oxygen is only a surface contaminant.

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Nickel oxide

In this case we only change oxygen percentage in our plasma.We are studying the growth kinetics, so it is interesting to see how crystal structure is changed with thickness.And we ask ourselves if different bias (negative voltage in the substrate to attract some ions) has an important role or not.

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Nickel oxide

Yes, we have structural evolution with thickness, and with bias in some extent.Variation with thickness: substrate imposes internal stresses.Variation with bias: ion bombardment changes preferential orientation until some point is reached. After that, it shall consume everything!

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Nickel oxide

There is an influence of oxygen content, there is a distortion of crystal structure.Indeed, at same bias or at same thickness, oxygen promotes or avoids some orientations, so we can distinguish two discharge regimes.

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Nickel oxide

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Future projects

Synchrotron facility in Campinas (Brazil).X-ray beam with high intensity and good properties.Useful to measure in-situ thin film growth.Understanding of nucleation processes, structural changes with time.

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Future projects

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Future projects

Development of NiO (nickel oxide) with new techniques, like HiPIMS.Understanding of growth kinetics and residual stresses.Application to solar cells: photovoltaic devices.Theoretical study and experimental development of Mott-Hubbard insulators with NiO in order to apply in the field of microelectronics.

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Personal project

Elaboration of papers related to NiO and CrN compounds.Improve the Nantes-Rosario relationship with more collaboration:-Aluminum nitride growth in Campinas-Preliminary work with metamaterials

Find a new job, a permanent position (university, R&D company) if it is possible.