I. Physika1isches lnstitut, Universitiit Stuttgart. W·7rxxl Stuttgart SO, Fed. Rep. of Gennany In oxygen doped germanium we find by phonon spectroscopy with superconducting tunnelling junctions [II (Fig.I) a series of states from 0.18 meV up to 4.08 meV above the ground state (Fig.3). The sequence can be approximated by a free rotation of the interstitial oxygen atom (
Silicon nanowires of various diameters
were irradiated with 100 keV and 300 keV Ar+ ions on a
rotatable and heatable stage. Irradiation at elevated temperatures
above 300 °C retains the geometry of the nanostructure and sputtering
can be gauged accurately. The diameter dependence of the sputtering
shows a maximum if the ion range matches the nanowire diameter, which
is in good agreement with Monte Carlo simulations based on binary
collisions. Nanowires irradiated at room temperature, however, amorphize
and deform plastically. So far, plastic deformation has not been observed
in bulk silicon at such low ion energies. The magnitude and direction
of the deformation is independent of the ion-beam direction and cannot
be explained with mass-transport in a binary collision cascade but
only by collective movement of atoms in the collision cascade with
the given boundary conditions of a high surface to volume ratio.
In
this letter, we demonstrate the formation of unique Ga/GaAs/Si nanowire
heterostructures, which were successfully implemented in nanoscale
light-emitting devices with visible room temperature electroluminescence.
Based on our recent approach for the integration of InAs/Si heterostructures
into Si nanowires by ion implantation and flash lamp annealing, we
developed a routine that has proven to be suitable for the monolithic
integration of GaAs nanocrystallite segments into the core of silicon
nanowires. The formation of a Ga segment adjacent to longer GaAs nanocrystallites
resulted in Schottky-diode-like I/V characteristics with distinct electroluminescence originating from
the GaAs nanocrystallite for the nanowire device operated in the reverse
breakdown regime. The observed electroluminescence was ascribed to
radiative band-to-band recombinations resulting in distinct emission
peaks and a low contribution due to intraband transition, which were
also observed under forward bias. Simulations of the obtained nanowire
heterostructure confirmed the proposed impact ionization process responsible
for hot carrier luminescence. This approach may enable a new route
for on-chip photonic devices used for light emission or detection
purposes.
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