Dr. Shannon Hill received his B.S. in physics from Washington University in St. Louis, MO in 1992. While there, he worked in an ultrasonics laboratory assisting in the development of non-destructive, quantitative analysis techniques for in situ evaluation of fatigue in now-commonplace composite materials and in vivo imaging of ischemic damage to the human heart. His Master’s work at Rice University centered on using highly-excited atoms (Rydberg states with principal quantum number n=100 to n=1100) to study ultra-low energy (≤100 µeV) electron-molecule scattering. He was awarded his Ph.D. in 1998 from Rice University for demonstrating a new microlithography technique using a beam of metastable Ar atoms to pattern hydrogen-passivated silicon surfaces and self-assembled monolayers.
During his first postdoctoral position at Rice University he supervised several projects. This included the first direct measurements of lifetime and decay dynamics of extremely long-lived negative ionic species using a Penning ion trap. He also participated in experimental and theoretical studies of the resonant ionization of highly-excited Xe atoms incident on a metal surface and the influence of strong electric fields on the ionization rates of atoms in Rydberg states by both 300 K blackbody radiation and molecular collisions.
Dr. Hill began his career at NIST in 2000 as an NRC Postdoctoral Fellow working with Jabez McClelland in the Electron Physics Group. Here he designed and build a so called “atom-on-demand source” consisting of a magneto-optical trap (MOT) for chromium with a fluorescence-detection efficiency sufficient to rapidly discriminate between zero, one, two, or more atoms in the trap. This allowed active feedback control of the otherwise stochastic loading and loss processes of the MOT to the point where single-atom occupancy could be guaranteed with over 98% probability at all times. Practical implementation of this deterministic atom source was established by extracting single atoms at rates up to 10 Hz with 98% fidelity and by demonstrating single-atom transfer to an overlapping standing-wave dipole trap.
Dr. Hill was also part of the team that first demonstrated a novel source of low-energy ions with a brightness comparable to conventional liquid-metal ion sources by photoionization of the atoms in a MOT. This magneto-optical trap-based ion source (MOTIS) has several potential advantages over traditional sources (typically limited to Ga+) including lower ultimate emittance leading to smaller focal spot size, ability to produce a range of ionic species (including heavy and light noble gases) and a much narrower energy spread (approximately 0.1 eV). Furthermore, by applying the same techniques used to create a deterministic source of atoms, a deterministic ion source could be realized that would allow, for example, precision doping of semiconductor nanostructures.
Since 2004, Dr. Hill's research has focused primarily on issues relating to the commercialization of extreme-ultraviolet (EUV) lithography, which is considered one of the leading technologies for next-generation lithography. This work has included characterization of the saturation behavior of photodiodes when used to measure the short (20 ns to 200 ns) but very high peak intensity (1 kW/cm2 to100 kW/cm2) pulsed output of typical EUV sources. His current efforts are focused on understanding the processes leading to and methods for measuring the degradation of the optics used in EUV lithography systems.
Sensor Science Division
Ultraviolet Radiation Group
2000-present, NIST, Gaithersburg, MD
1999-2000, Rice University, Houston, TX
Ph.D. Physics, Rice University, Houston, TX
M.A. Physcis, Rice University, Houston, TX
B.S. Physics, Washington University, St. Louis, MO