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.
Institute for Optical Sciences and Departments of Physics and Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada.
Maher
M
Harb
Ralph
R
Ernstorfer
Christoph T
CT
Hebeisen
Germán
G
Sciaini
Weina
W
Peng
Thibault
T
Dartigalongue
Mark A
MA
Eriksson
Max G
MG
Lagally
Sergei G
SG
Kruglik
R J Dwayne
RJ
Miller