people
|Faculty
|Hrvoje Petek
 |
Hrvoje Petek Department of Physics and Astronomy |
Carrier dynamics in solid-state materials
Fundamental electrical, magnetic, and optical properties
of solid-state materials are determined by the dynamical response
of carriers to internal and external fields. The near-equilibrium
properties of carriers in most materials are well understood
from classical studies of transport and optical conductivity.
However, due to strong interactions of carriers among themselves
and with the lattice, studies of nonequlibrium dynamics on
femtosecond time scales (10 - 15 s) are just emerging. In our
group, a particularly versatile and powerful technique, time-resolved
two-photon photoemission (TR-2PP) spectroscopy, has been developed
for studying the carrier excitation and relaxation processes
in solid-state materials. With this technique we are investigating
the quantum mechanical phase and carrier population relaxation
times in metals, and for intrinsic and adsorbate induced surface
states on metals. Of particular interest are the physical
processes that induce e-h pair decoherence, since they impose
limits on time scales for quantum control of carriers through
the optical phase of the excitation light. The manipulation
of the carrier phase with light may lead to applications such
as ultrafast (>10 THz) switching and information processing,
as well as, atomic manipulation of matter, and therefore,
it is of great interest for advanced technologies in the 21st
century.
Ultrafast microscopy
Understanding of the carrier dynamics under quantum confinement
is a key to advancing nanoscale science and technology. Although
with the existing scanning probe techniques we can potentially
study dynamics of individual nanostructures, there is also
a clear need for ultrafast imaging microscopic techniques
in studies of dynamics in complex systems of nanostructures
that could comprise ultrafast electronic or optical device.
Photoemission electron microscopy (PEEM) is a well-developed
surface science technique for imaging nanostructures on metal
and semiconductor surfaces. In combination with femtosecond
pump-probe excitation, we intend to develop time-resolved
PEEM with potentially <1 fs, <20 nm, <100 meV carrier energy
resolution. This technique will be applied to fundamental
studies of carrier dynamics in individual nanostructures and
coupled nanocomposite systems, in order to understand the
fundamental physics of hot carriers in low dimensional systems
and to develop advanced device concepts.
Atomic manipulation with light
Electronic excitation of clean or adsorbate covered metal
surfaces can impulsively turn-on large mechanical forces that
lead to mass transport parallel or perpendicular to the surface.
When such forces are harnessed properly, they can be used
for atomic manipulation or even atomic switching. Although
there are now several examples of atomic manipulation with
STM techniques, much less is known about how equivalent, but
much larger scale manipulation could be accomplished with
light. The recent observation and demonstration of quantum
control of motion of Cs atoms above a Cu(111) surface by our
group provides a proof-of-principle for the atomic manipulation
of surfaces with light. Such studies are being extended to
identify the factors that govern the electronic relaxation
of adsorbates on metal surfaces, which can effectively quench
the nuclear motion.
Selected Publications
"Femtosecond Imaging of Surface Plasmon Dynamics in a Nanostructured Silver Film," A. Kubo, K. Onda, H. Petek, Z. Sun, Y. Jung, and H. K. Kim, Nano Letters, 2005, 5, (6), 1123-1127
"Wet Electrons at the H2O/TiO2(110) Surface," K. Onda, B. Li, J. Zhao, K. Jordan, J. Yang, H. Petek, Science, 2005, 308, 1154-1158
"The birth of a quasi-article in silicon observed in time frequency space," M. Hase, M. Kitajima, A. M. Constantinesch, and H. Petek, Nature, 2003, 426, 51-54
"Surface femtochemistry; observation and quantum control of frustrated desorption of alkali atoms from noble metals," H. Petek and S. Ogawa, Ann. Rev. Phys. Chem., 2002, 53, 507-531
"Surface femtochemistry: Frustrated desorption of alkali atoms from noble metals," H. Petek, H. Nagano, M. J. Weida, and S. Ogawa, J. Phys. Chem. B, 2001, 105, 6767-6779
"Real-time observation of adsorbate atom motion above a metal surface," H. Petek, M. J. Weid, H. Nagano, and S. Ogawa, Science, 2000, 288, 1402-1404
"Femtosecond time-resolved two-photon photoemission studies of electron dynamics in," H. Petek and S. Ogawa, Prog. in Surf. Sci., 1997, 56, 239-310