Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 76: Ultrafast Electron and spin dynamics at interfaces III
O 76.2: Talk
Wednesday, March 14, 2018, 17:45–18:00, MA 005
Time-resolved photoelectron spectroscopy with high-order harmonics: Surface photovoltage shift at SiO2/Si(001) interfaces with nonlinear optical excitations — •Robin Kamrla1,2, Cheng-Tien Chiang1,2, Andreas Trützschler1,2, Michael Huth2, Frank Oliver Schumann2, and Wolf Widdra1,2 — 1Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale), Germany — 2Max Planck Institute of Microstructure Physics, Halle (Saale), Germany
We investigate the fluence and doping dependence of surface photovoltage shifts (SPV) at SiO2/Si(001) interfaces. Charge carriers are excited by 300 fs laser pulses at repetition rates of 0.2 to 0.7 MHz with photon energies of hνpump = 1.2 or 2.4 eV, and subsequently probed by high-order harmonics with hνprobe = 22.6 eV. On SiO2/p -Si(001) we observe a SPV of 250 meV upon excitation with hνpump=1.2 eV towards higher energies, whereas on SiO2/n -Si(001) the SPV reverses its sign and has a smaller magnitude of 140 meV. Upon excitation with hνpump = 2.4 eV a maximum SPV at SiO2/p -Si(001) of 350 meV is observed. Moreover, SPV at SiO2/p -Si(001) shows a nonlinear fluence dependence at hνpump = 1.2 eV, which significantly differs from that of hνpump = 2.4 eV. In this talk the dynamics of SPV as well as its fluence dependence will be discussed.