167 research outputs found
Evidence for Kinetic Limitations as a Controlling Factor of Ge Pyramid Formation: a Study of Structural Features of Ge/Si(001) Wetting Layer Formed by Ge Deposition at Room Temperature Followed by Annealing at 600 {\deg}C
The article presents an experimental study of an issue of whether the
formation of arrays of Ge quantum dots on the Si(001) surface is an equilibrium
process or it is kinetically controlled. We deposited Ge on Si(001) at the room
temperature and explored crystallization of the disordered Ge film as a result
of annealing at 600 {\deg}C. The experiment has demonstrated that the
Ge/Si(001) film formed in the conditions of an isolated system consists of the
standard patched wetting layer and large droplike clusters of Ge rather than of
huts or domes which appear when a film is grown in a flux of Ge atoms arriving
on its surface. We conclude that the growth of the pyramids appearing at
temperatures greater than 600 {\deg}C is controlled by kinetics rather than
thermodynamic equilibrium whereas the wetting layer is an equilibrium
structure.Comment: Accepted for publication in Nanoscale Research Letter
Influence of Photoexcitation Depth on Luminescence Spectra of Bulk GaAs Single Crystals and Defect Structure Characterization
The results of investigation of bulk GaAs photoluminescence are presented
taken from near-surface layers of different thicknesses using for excitation
the light with the wavelengths which are close but some greater than the
excitonic absorption resonances (so-called bulk photoexcitation). Only the
excitonic and band-edge luminescence is seen under the interband excitation,
while under the bulk excitation, the spectra are much more informative. The
interband excited spectra of all the samples investigated in the present work
are practically identical, whereas the bulk excited PL spectra are different
for different samples and excitation depths and provide the information on the
deep-level point defect composition of the bulk materials.Comment: Aalborg Summer School on Nonlinear Optics, Aalborg, Denmark, 7-12
August 199
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