Master assignments

Fluorine doped tin oxide microprocessing

With global energy consumption rising and reserves of conventional energy sources such as coal and oil diminishing, we will inevitably have to switch more and more to renewable energy sources. The sun is an energy source with great potential in this respect: the global energy consumption is almost negligible compared to the amount of solar energy that irradiates the land masses on earth. However the sun is not always shining, while there is always energy consumption. Before solar energy can replace most of the fossil fuels, a way has to be found to store the energy harvested from the sun on a large scale. A promising option for this is storing the energy in a chemical bond: the solar energy can be used to electrolyze water to produce hydrogen and oxygen. They can be converted back to water to produce the electricity when needed.

Solar energy absorption and hydrogen production can be combined in a single microstructured device. However not all absorbing materials are stable in these conditions, so they need a protective coating. This coating must permit light and electrons to pass through it. Also it cannot be a very expensive material.

Fluorine doped tin oxide (FTO) satisfies all of these requirements. However applying it as a thin film on microstructures, and partially removing it to obtain a specific pattern has been reported but is not trivial.

Assignment

Several methods for applying FTO have been reported in the literature [1], including sputtering and dip coating. Reproducing these results will be part of the assignment. Also it has to be tested if these methods are suitable for applying the film on microstructures. The results can be compared to layers that have been applied commercially by chemical vapor deposition. Sputtering is done inside the cleanroom in the Nanolab, and to use the equipment the student will have to familiarize himself/herself with the cleanroom procedures.

This is also necessary for the partial removal of the material, which will be done by reactive ion etching. The method is experimental and has been shown to work, but the parameters have to be optimized.

The resulting films have to be characterized for electrical and optical performance, and tested for chemical passivation performance.

A background in material science and/or micro/nanofabrication is preferred.

Contact

If you are interested in this assignment please contact Pieter Westerik, who is doing a PhD research in the MCS group: p.j.westerik

References

[1] T. Jäger, B. Bissig, M. D̂beli, A.N. Tiwari, and Y.E. Romanyuk. Thin films of SnO2:F by reactive magnetron sputtering with rapid thermal post-annealing. Thin Solid Films, 553(0):21-25, 2014. ISSN 0040-6090. http://dx.doi.org/10.1016/j.tsf.2013.12.038.