Organic molecular films on metal and graphene surfaces studied with leem
Promotion date: 11. January 2012
Promotor: Prof.dr.ir. Bene Poelsema
Assistant promotors: Dr. Raoul van Gastel, Dr. Gregor Hlawacek
A novel approach is investigated to the functionalization of substrates. The aim is to directly image the formation of patterns with Low Energy Electron Microscopy (LEEM), and to expose and quantify the relevant thermodynamic growth parameters. Features that are relevant to the positioning of the self-assembling entities can also be identified through this approach.
Three organic molecules - trimesic acid (TMA) , 4,4'-biphenyldicarboxylic acid (BDA), and para-sexiphenyl (6P), and two substrates, Cu(001) and graphene - are used in this work.
Influence of the surface temperature on growth is studied. Temporal evolution experiments provided information on stability of BDA-domains. A further refinement of the balance between the molecule-substrate interactions on the one hand, and the molecule-molecule interactions on the other hand, was investigated.
Having exposed the role of the substrate, the same experiments were repeated with the 6P molecule. Its structure and dynamics are investigated on graphene. It is found that at low temperature 6P single layer high domains possessed high mobility. Further deposition at low temperatures led to the formation of few layers high domains of 6P.
Last but not the least, influence of the surface temperature on growth is studied. At room and above temperatures needle-like 6P structures formed on graphene. Above a certain temperature no 6P structures were formed on graphene.
What are the advantages of the approach you used in this thesis project?
Using low energy electron microscopy allows one to follow the growth process in real-time with high resolution. Graphene is a popular semi-conducting material of which the characteristics are known only in general terms. Experimental work using vapour deposition can lead to expected as well as to not expected results. Defects and the impact on the performance of devices are interesting. It is still needed to understand the mechanisms underlying these phenomena.
Did you manage to have some nice publications?
In five well-rated magazines my findings appeared: Physical Review Letters B, Nanoletters, Journal of Chemical Physics, IBM Journal of Research and Development, and Surface Science.
I was a speaker on the Materials Research Society Conference, 2008 in San Fransisco, also at the LEEM and PEEM conference, 2009 in Italy and at the big Surface Science & Interfaces conference in Stockholm.
How did you develop personally as a researcher and scientist?
No matter how smart you are, experiments sometimes fail. I value this much more positively now as it is a crucial part of scientific research.
Patience and constant thinking are important when you are down. Besides that we work as a part of the research group not in isolation. Therefore we improve our research and personally develop ourselves by collaborating with the group members, by learning from their experiences and knowledge. We also share responsibilities at different levels, from supervisor, colleagues and technical support members. Having good people to work with always influence you in a positive way.
What, in your opinion, is important for Mesa+ to stay successful in future?
I really liked the Mesa+ Day for broadening my view. Also I enjoyed several speakers from other fields, especially chemical catalyst experts. Sharing the knowledge is very rewarding and an enriching experience.
Most of the time I felt a group member, responsible for my work and that of the group. There is not much time left to start extra activities. I guess the group leader and board should find collaboration possibilities in the first place. PhD’s can find project specific collaboration possibilities on their own initiative.
What are your future plans?
Right now, I am working at ASML as an application engineer, sorting out machine related challenges to optimize customers’ processes. This gives me opportunities of collaborations and consultations inside and outside my company. I like the social way of using my expertises and knowledge to help customers. If you ask me what is this job all about, I would say “always acquiring and conveying knowledge”.