Electron Transport in Quantum Dots

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9501438 Westervelt Coupled two and three quantum dots, artificial molecules, including chains and rings of dots will be fabricated on gallium- arsenide/aluminum-gallium-arsenide heterostructures from UCSB. Such structures on semiconductors will enable the PI to compensate for the effect of impurities and defects on the energy of the electrons and the dot to dot coupling. Coulomb blockade and dot capacitance at ultra-low temperatures will be used as spectroscopic tools for electron states in single and couple quantum dots. Additional probes such as localized microwave excitation via miniaturized striplines, and spatially resolved scanning probe measurements currently under development will be used to characterize electron states and transport in single and coupled dots. The objective is to elucidate the nature of electron states in coupled dots and to search for possible collective quantum phenomena. The behavior of electrons inside these structures is of great current interest, both for practical and for fundamental reasons. The controlled motion of single electrons through coupled quantum dots is the basis for new approaches to electronics and computation. %%% This project investigates semiconductor "quantum dot", structures which are so small that they are also referred to as artificial atoms and molecules. Their fabrication is complex and involves collaboration between workers at Harvard and UC Santa Barbara. The behavior of electrons inside these structures is of great current interest, both for practical and for fundamental reasons. The controlled motion of single electrons through coupled quantum dots is the basis for new approaches to electronics and computation. For example, a goal is to develop single electron devices in which each bit is represented by a single electron, whose state may be optically switched. Unlike "real" molecules, the size and cou pling between the quantum dots can be varied by fabrication methods to produce new phenomena not normally found in molecules. Measurements of the Coulomb blockade and dot capacitance at ultra-low temperatures will be used as spectroscopic tools for electron states in single and coupled quantum dots. ***