Analyse der Luft

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Carrier relaxation in epitaxial graphene photoexcited near the Dirac point

We study the carrier dynamics in epitaxially grown graphene in the range of photon energies from 10 to 250 meV. The experiments complemented by microscopic modeling reveal that the carrier relaxation is significantly slowed down as the photon energy is tuned to values below the optical-phonon frequency; however, owing to the presence of hot carriers, optical-phonon emission is still the predominant relaxation process. For photon energies about twice the value of the Fermi energy, a transition from pump-induced transmission to pump-induced absorption occurs due to the interplay of interband and intraband processes.     

Preparation of P-rich InP surfaces via MOCVD and surface characterization in UHV

For the first time direct contamination-free transfer to UHV was achieved for the P-rich InP(100) surface that is the easiest to prepare and control in the MOCVD environment. To avoid contamination during transfer a commercial MOCVD apparatus was modified to allow for transfer of samples to the 10^-9 mbar UHV range within a very short time (less than 20 s) [1]. Epitaxial InP(100) films were prepared with TBP (tertiarybutylphosphine) and TMIn (trimethylindium) as precursors. In situ reflectance anisotropy spectroscopy (RAS) was carried out in the MOCVD environment. After transfer of the sample to UHV the same RAS spectrum was recovered. Auger-electron spectra (AES) confirmed the P-termination of the surface reconstructions suggested by RAS. Received: 19 October 1998 / Accepted: 21 April 1999 / Published online: 14 July 1999     

Apparate zur Bestimmung der Kohlens?ure

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