Electronically driven structure changes of Si captured by femtosecond electron diffraction.
The excitation of a high density of carriers in semiconductors can induce an order-to-disorder phase transition due to changes in the potential-energy landscape of the lattice. We report the first direct resolution of the structural details of this phenomenon in freestanding films of polycrystalline and (001)-oriented crystalline Si, using 200-fs electron pulses. At excitation levels greater than approximately 6% of the valence electron density, the crystalline structure of the lattice is lost in <500 fs, a time scale indicative of an electronically driven phase transition. We find that the relaxation process along the modified potential is not inertial but rather involves multiple scattering towards the disordered state.
Harb
Maher
M
Institute for Optical Sciences and Departments of Physics and Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada.
Ernstorfer
Ralph
R
Hebeisen
Christoph T
CT
Sciaini
Germán
G
Peng
Weina
W
Dartigalongue
Thibault
T
Eriksson
Mark A
MA
Lagally
Max G
MG
Kruglik
Sergei G
SG
Miller
R J Dwayne
RJ