Letter of Motivation

Letter of Motivation

As a student, who studies Physics, I am curious about various physic phenomena, and always willing to see the newest and the most mysterious phenomenon. This was my motivation to leave Vietnam and Russia to join Erasmus Mundus program Nanoscience & Nanotechnology to learn more about physics, quantum physics, nanoscience and nanotechnology. My curiosity and love for physics lead me to concentrate mainly on mesoscopic physics, quantum coherence transport of electrons, quantum dots and graphene.

In addition to these theoretical knoledges, I also acknowledge the importance of practical skill in using preparation, ranging from top-down, like e-beam lithography, dry etching techniques to bottom-up ones, like self-assembly and characterization techniques, like AFM, NanoSEM, or Raman spectroscopy to equip myself for my future career in nanoscience as a physicist. In the next few paragraphs, I will show you how experienced I am in using some important techniques used in experiments with graphene, and also present briefly about my academic success during the last two years.

Firstly, I have a lot of experiences in using e-beam lithography thanks to my Master thesis, which concerns with long range proximity effect in ferromagnetic materials. For this thesis, I have to work daily with different sputtering, etching systems and especially with e-beam lithography in clean room to prepare samples for measurement at low temperature. Working with this state-of-art equipment is both exciting and challenging. It is exciting, because with this kind of equipment, I can write a structure as small as 50nm, or even smaller. And in nanoscience, all objects have a size in nanoscale.

Therefore, mastering in using this equipment is the most important key to go further in academic career in nanoscience and nanotechnology field. And now, before ending my thesis, I can say that I use my time in the smartest way to learn as much as possible about e-beam lithography, both in how to use it, and what kind of technical problems can happen with it, and more or less how to fix it. But working with e-beam is also challenging, because it is not as simple as writing some letters with pen, as illustrated in any literature about e-beam lithography.

To receive the best resolution and high quality samples in the most economic way in time and money, it requires a lot of knowledge about all parameters, which can contribute into the final result. Therefore, a careful examination of different parameters is highly important. In my work in Leiden with e-beam, I have succeeded to reduce a writing time for my sample from 12 hours to 6 hours by varying a settling time. And this dramatic reduction in writing time has enhanced a lot in my work efficiency. On the other hand, as my sample requires an etching step during preparation, I have some experiences with Argon ion beam etchers.

Compared to e-beam lithography, this machine is less complicated, but sometimes still problematic. And the biggest issue, which I faced with, is a thermal problem created by collision of ions. The heat can be high enough to polymerize my photoresist and make it too hard to remove. After some times to brainstorm, a simple solution was found; it requires liquid Nitrogen to cool down sample. But applying liquid Nitrogen is also tricky; a flux must be high enough to cool down efficiently, but not too high to detach a covered photoresist.

In addition to these practical skills, I have learnt and good background in different fields, Physics, Chemistry. And fortunately, in the last two years, I’ve passed with great successes in these subjects, with best results in Physics. Some of my best results are in Mesoscopic Physics with 8. 5/10 in TuDelft and 16/20 (rank B) in KULeuven, Scanning Probe Microscopy with 16/20 (rank B) Advanced Nano-electronic concept with 15/20, and Statistical Physics with 10/10 in Leiden. Therefore, I have a strong confidence about my strong physic background, to face with tough problems in quantum world, like quantum dots or graphene.

In addition to a strong interest in physics in nanoscale, I even have an ambition to contribute into realizing potentials of graphene in industry. But to fulfill this dream it is crucial to learn, to investigate more and more about properties of this material. And once after reading an article about the effect of zig-zag edge on magnetic properties of graphene (1), I have a dream to combine this discovery with my recent master thesis project in spin triplet supercurrent in ferromagnetic materials. If Prof.

Eschrig is true about a potential of ferromagnetic materials in spintronics as a spin filter (2), I also have an imagination to apply graphene in this role as well. Then, by varying the type of edges, graphene can generate different types of Cooper pair, with zero and non-zero spin. This plan is still quite out of my reach, especially when both two mentioned topics, long-range proximity effect and ferromagnetic properties of graphene, are still in debate, and have a lot of challenges to overcome, but it is really nice project to follow, at least from my point of view.

In the end, after presenting about my practical skills, theoretical knowledge and also my ambition to progress in nanoscience, I hope you also recognize me as a strong candidate with great potential for this position. From my side, to join your group, listen and learn from experts in quatum nanoelectronics is my pride, and my dream. I believe that only in this prestige academic environment, my skills and knowledge will be improved dramatically. Le Quang Toai. References: 1. Y. Wang, et al. , Nano Lett. , 9 (1), pp 220-224, 2009. 2. M. Eschrig, et al. , Physics Today, 1, vol. 64, 2011.