Angle-Resolved Photoemission from Nanostructures

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Non-Technical Abstract: One of the main goals of nanotechnology is the design of new materials with tailored electronic properties. This project focuses on designing materials with one-dimensional character, such as chains of metal atoms at silicon surfaces. These may be viewed as the ultimate nanowires. The properties of electrons in nanostructures will be determined by photoemission with synchrotron radiation and by two-photon photoemission with lasers. An ambitious attempt will be made to directly determine quantum mechanical behavior of electrons in nanowires from the experiments. The broader impact will be in three areas: 1) Education of graduate students and high school teachers through an efficient way to bring nanoscience to high school students, 2) Fabrication methods for new materials in microelectronics by extension of silicon technology to a few nanometers and providing atomic precision via self-assembly, and 3) International experience for graduate students and postdocs by collaborations with European universities. This will give them an edge in the high-tech job market, where multinational companies play a dominant role. Technical Abstract: This project is focused on atomic chains at semiconductor surfaces. These "ultimate nanowires" provide an ideal testbed for basic one-dimensional phenomena, serve as building blocks for atomic-scale electronic devices, and provide new materials with one-dimensional character. The discovery of a versatile class of atomic chain structures under prior NSF support has created many opportunities for synthesizing one-dimensional structures. Several new directions will be pursued: 1) Doping of atom chains by substitution, as in HiTc compounds. 2) Chains of magnetic atoms, such as rare earths. 3) Empty states and femtosecond hot electron dynamics in atom chains from by two-photon photoemission. 4) Direct measurement of the electron wave function in a one-dimensional nanostructure from the Fourier transform of the photoemission pattern in k-space, using iterative phase retrieval. Broader impact this work can be expected in the following areas: 1) Education of graduate students and high school teachers, an efficient way to bring nanoscience to high school students. 2) Fabrication methods for new materials in microelectronics, extending silicon technology down to the single digit nanometer regime and providing atomic precision via self-assembly. 3) International experience for graduate students and postdocs by collaborations with European universities (Germany, Spain), where the PI has close connections. Such experience provides an edge in the high-tech job market, where multinational companies play a dominant role.