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Delayed auger recombination in silicon measured by time-resolved X-ray scattering
Jo, Wonhyuk,Landahl, Eric C.,Kim, Seongheun,Lee, Dong Ryeol,Lee, Sooheyong ELSEVIER 2018 CURRENT APPLIED PHYSICS Vol.18 No.11
<P>We report a new method of measuring the non-radiative recombination rate in bulk Silicon. Synchrotron time-resolved x-ray scattering (TRXS) combines femtometer spatial sensitivity with nanosecond time resolution to record the temporal evolution of a crystal lattice following intense ultrafast laser excitation. Modeling this data requires an Auger recombination time that is considerably slower than previous measurements, which were made at lower laser intensifies while probing only a relatively shallow surface depth. We attribute this difference to an enhanced Coulomb interaction that has been predicted to occur in bulk materials with high densities of photoexcited charge carriers.</P>
Delayed auger recombination in silicon measured by time-resolved X-ray scattering
조원혁,Eric C. Landahl,김성흔,이동렬,이수형 한국물리학회 2018 Current Applied Physics Vol.18 No.11
We report a new method of measuring the non-radiative recombination rate in bulk Silicon. Synchrotron timeresolved x-ray scattering (TRXS) combines femtometer spatial sensitivity with nanosecond time resolution to record the temporal evolution of a crystal lattice following intense ultrafast laser excitation. Modeling this data requires an Auger recombination time that is considerably slower than previous measurements, which were made at lower laser intensities while probing only a relatively shallow surface depth. We attribute this difference to an enhanced Coulomb interaction that has been predicted to occur in bulk materials with high densities of photoexcited charge carriers.
Jo, Wonhyuk,Lee, Sooheyong,Eom, Intae,Landahl, Eric C American Institute of Physics 2014 Review of scientific instruments Vol.85 No.12
<P>The ability to synchronize a femtosecond laser to x-ray pulses is crucial for performing ultrafast time-resolved x-ray scattering experiments at synchrotrons. Conventionally, the task has been achieved by locking a harmonic frequency of the laser oscillator to the storage ring master radio-frequency (RF). However, when the frequency mismatch between the two sources cannot be compensated by small adjustments to the laser cavity length, synchronization to a harmonic frequency requires modifying the optical components of the laser system. We demonstrate a novel synchronization scheme, which is a flexible alternative for synchronizing these two sources operating at arbitrarily different frequencies. First, we find the greatest common divisor (GCD) of the two frequencies that is still within the limited tuning range of the laser cavity length. The GCD is generated by dividing down from the storage ring RF, and is separately multiplied up to provide a feedback signal for synchronizing the laser cavity. Unique to our scheme, the GCD also serves as a harmonic RF source for the laser amplifier such that only laser oscillator pulses at fixed integer multiples of the storage ring RF are selected for amplification and delivery to experiments. Our method is implemented at the Photon Test Facility beamline of Pohang Light Source where timing-jitter less than 4 ps (r.m.s.) is measured using a new shot-to-shot method.</P>