Quantum Dot Low Temperature Measurement and Analysis Thesis

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Metadata	Details
Publication Date	2017-01-01
Journal	Lund University Publications Student Papers (Lund University)
Authors	Vidar Flodgren

Abstract

In this bachelor project, the electron transport within quantum dot transistor devices, whose barriers are electrostatically induced, was measured and analysed. The properties of devices with this particular architecture are not yet fully understood. We successfully synthesised several 150x50x50 nm of these devices, where the potential barrier gates are defined next to the nanowire to form the quantum dot island. These devices were trialled in a low temperature environment by the use of liquid helium and a dip rig in order to study the electron transport through the quantum dot of each device at a temperature of about 4.2 K. These electrostatically induced dots were able to show the Coulomb diamonds produced only within the range of n to n+4 number of electrons. The lever arm αɢ, ΔE between energy levels Eₙ, the self capacitance CΣ and the energy Eᴀᴅᴅ required to add another electron per diamond of each device were also determined. In general, each device showed the artificial atomic shell structure shown directly by the even-odd electron coupling principle determining the energy required to add additional electrons to the island. Due to time constraints, only two devices out of a total of 11 successfully synthesised were used in measurements. Measurements on the first device were used to explore the quantum dot behaviour induced by the potential barriers. The results from the second device showed that a dot could be induced without the barriers, prompting attempts to prove exactly how the second dot had been induced. It was found that the 350 nm distance between source and drain was sufficient to induce quantum dot behaviour.

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