arXiv subjects

Halina Krzyzanowska

Publications and source records attributed to Halina Krzyzanowska.

3 recordsLinked to original sources

arXiv2019

Influence of doping level on Brillouin oscillations in GaAs

Time-domain Brillouin scattering has proved to be an unique tool for determining depth dependent material properties. Here, we show the influence of doping level in GaAs on Brillouin oscillations. Measurements were performed on intrinsic, n-type and p-type GaAs samples. The results show high sensitivity of the amplitude of Brillouin oscillations to the doping concentration. The theoretical calculations are in a good agreement with the experimental data. This work provides an insight into the specific dopant profiling as a function of depth.

cond-mat.mtrl-sci↗

arXiv2019

Energy dependent amplitude of Brillouin oscillations in GaP

Gallium phosphide is an important indirect band gap material with variety of applications in optics ranging from LEDs to applications in GaP/Si based solar cells. We investigated GaP using ultrafast, pump-probe coherent acoustic phonon spectroscopy (time-domain Brillouin scattering). We measured the dependence of the amplitude of the differential reflectivity as modulated by coherent acoustic phonons (CAPs) as a function of laser probe energy and found that the amplitude of the coherent phonon oscillations varies non-monotonically near the direct gap transition at the $Γ$ point. A theoretical model is developed which quantitatively explains the experimental data and shows that one can use coherent phonon spectroscopy to provide detailed information about the electronic structure, the dielectric function and optical transitions in indirect band gap materials. Our calculations show that the modelling of experimental results is extremely sensitive to the wavelength dependent dielectric function and its derivatives.

cond-mat.mtrl-sci↗

arXiv2019

On the interpretation of manifold ultrafast dynamics in supported graphene

Understanding the ultrafast carrier dynamics of graphene on a substrate is a fundamental step in the development of graphene based opto-electronic devices. Here, we present ultrafast pump-probe measurements of supported graphene on quartz for a range of pump fluences that enable us to observe both decreased and enhanced probe transmission regimes on a femtosecond timescale. Unexpectedly, at an intermediate pump fluence, an order of magnitude decrease in the relaxation time constant of the differential transmission is observed. By employing a number of different models to interpret our experimental data, we demonstrate the importance of considering both intra- and inter-band contributions to the dynamical optical conductivity in order to extract a more physical relaxation time constant of hot optical phonons.

cond-mat.mes-hall↗