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The Nojeh Nanostructure Group investigates the effects inherent to reduced scales and dimensions, such as the strong presence of quantum phenomena, to develop innovative devices and applications. This research group is particularly interested in how electrons and photons behave in nanostructures and interact with each other in them. Often they see unexpected effects that are not only of great scientific interest, but can enable real-life practical applications. They spend a lot of time and effort on a particular kind of nanostructure known as carbon nanotubes. These are very small structures that can be 100 thousand times thinner than a human hair. A grain of floating dust can be hundreds or even thousands of times larger than these structures. Therefore, these structures must be investigated in clean, well-controlled environments such as ultra-high vacuum systems. Nanostructures have unique properties, be it electrical, mechanical, optical or thermal. And one can exploit these properties for a variety of applications.
A nanofabrication clean room is used to prepare a silicon wafer for carbon nanotube growth. A small piece of the wafer, containing growth catalyst, is placed into a chemical vapour deposition system, where a high-temperature process for growing carbon nanotubes takes place. Depending on the different flow rates and the composition of the gases used, the lab can control the growth rate. Heat-up the substrate, break-down the gases and the broken-down gasses can get deposited onto the substrate to form carbon nanotubes.
By focusing a laser beam onto a nanotube forest you can emit electrons. A phenomenon the lab has recently discovered, which they have coined “Heat Trap”, is that nano-forests can trap heat generated by the laser in a way that conventional metals can’t.
The lab is collaborating with physicists to look into how this heat trapping really works at the quantum mechanical level. Quantum mechanics is strongly present in nanostructures and is at the root of much of their surprising behavior. Carbon nanotubes, in particular, are a great vehicle to study quantum phenomena.
Researchers in this lab work both on theory and experiments to explore the phenomenon. Calculating the optical and electrical properties of carbon nanotubes, Saloome Motavas predicts which wavelengths of light can be absorbed better by nanotubes through modelling and simulation, while Parham Yaghoobi experimentally measures how different wavelengths are absorbed and can compare some of the results with Saloome's predictions.
The Heat Trap effect opens the door to a multitude of applications including new types of electronics, imaging systems, even alternative energy generation systems, and is a very good example of the unique properties of nanostructures. They are small but have huge potential.