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Abstract:
There is a recent interest in nanoscale materials, in particular,
nanotubes based not only on carbon. In this study, photoemission spectra
of single MoS2 nanotubes deposited on a Si surface were recorded in
order to explain their electronic structure. The photoelectrons were
excited by a femtosecond laser oscillator resulting in two-photon
photoemission. A spectromicroscopic technique based on imaging
time-of-flight detection was used to record the spatially resolved
photoelectron spectra. Self-consistent electronic structure calculations
for MoS2 slabs using the full potential linear augmented plane wave
method are used to explain the peculiarities of the observed spectra. It
turns out that the MoS2 nanotubes are semiconducting with a band gap of
about 1 eV. The two-photon transitions proceed through intermediate
states in a region with high density of states; this gives rise to a
high photoemission intensity. (c) 2006 American Institute of Physics.