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Paul Rusu (promotion date: 25 October 2007)

Charged transfer and dipole formation at metal-organic interfaces

Promotion date: 25 October 2007

Basically my thesis is about metal-organic interfaces. The work is motivated by recent developments in molecular electronics, where organic semiconductors constitute active layers in various electronic devices such as thin film transistors, solar cells or light-emitting diodes.

We all know that electric charges travel well through a metal, that’s why the traditional contacts are made of metals. However, in such devices, the transport across the interfaces formed between metal electrodes and organic materials determines the device performance.

The charges need to overcome an energy barrier when transported from the metal contacts to the organic layers, so it is important to study and model the formation of such barriers at metal-organic interfaces. That was the main objective of the work.

Why is an organic material so important?

Such devices made from organic materials present very nice features. For instance, in a light-emitting diode the electrons and holes that are injected through the metal contacts drift through the molecular layers. They recombine and emitting light. Depending on the type of the organic material, light can be emitted in all colours of the spectrum. Therefore full colour displays can be made using this technique. Such displays can be flexible; they are cheaper and have low power consumption.

What was your specific contribution in this kind of research?

We do theoretical work. We sort of characterized several types of organic molecules adsorbed on several metal surfaces. The characterization is important for the experimental work that is to follow. Because of such theoretical studies people will know what to expect. A drawback in this kind of work is that you cannot perform calculations on very large molecules; the resources of computer power are limited for that. But very useful output can be extracted.

Did you enjoy your work?

Oh yes, very much. I came from a different field altogether, so it presented a challenge as well.

Where are you from?

I am from Romania.

Why did you apply for a PhD position at Twente University?

I was interested in the subject. I checked the internet and read abstracts. Then I looked for possible vacancies. I sent my CV, applied, was interviewed and accepted.

Did you experience any setbacks?

On the whole I was quite happy. Some things took a bit longer than I would have wished, but I suppose that’s normal. I guess it would have been good to have started writing a bit earlier, because we had lots of results. Some I haven’t included in my thesis, but we’ll publish these results later. Writing takes a lot of time. I had some publications in Physical Review and the Journal of Physical Chemistry.

What are your plans?

I am thinking about this. I still have a contract with the group for a postdoc afterwards for one year. After that I might try somewhere in industry in a research company to see the other side of research. I got used to the Netherlands and I would like to stay here. But I haven’t thought about it too much.

What do you like about the Netherlands?

The people are open and on the whole friendly, and nearly everybody speaks English.

I am not so concerned about the weather. In Romania the summers are very hot. I prefer the kind of weather we have here, but not when having a holiday. You might end up with two weeks in the rain. Since the Netherlands is not so large, you can easily go to another country and sniff a different culture.

For the summary of the thesis, click here