5 research outputs found
Crystal Phase Selective Growth in GaAs/InAs Core–Shell Nanowires
We present a novel type of core–shell
nanowires in which
only certain parts of the core are covered by the shell. This is achieved
by the crystal phase selective growth of the InAs shell on zinc blende
GaAs nanowires with controlled wurtzite inclusions. The shell grows
on the zinc blende phase, but its growth is hindered on the wurtzite
crystal phase. Nucleation of InAs occurs exclusively on the zinc blende
GaAs regions. The wurtzite segments are placed inside self-catalyzed
GaAs nanowires by partially consuming and refilling the Ga droplet.
The crystal phase selective growth of InAs on the side facets of the
GaAs nanowires is explained by the local environment of each new In
atom. Because of unbalanced neighbors on the wurtzite side facets,
the growth of a highly lattice mismatched material is hindered. This
happens not only on the wurtzite segments, but also on regions being
characterized by a high density of twins
Mode of Growth of Ultrathin Topological Insulator Bi<sub>2</sub>Te<sub>3</sub> Films on Si (111) Substrates
Layered materials such as graphene, bi-, and multilayer
graphene
as well as various compounds of topological insulators are currently
in the focus of interest due to their extraordinary physical properties
related to Dirac surface states. The ability to grow thin films of
these complex layered materials is the key to explore their fundamental
phenomena giving insights into modern solid-state physics. However,
complex materials composed of layers only weakly bonded via van der
Waals forces offer unmatched challenges for the deposition of thin
epitaxial films. Here, we report on the growth of Bi<sub>2</sub>Te<sub>3</sub> ultrathin films on Si (111) substrates using molecular beam epitaxy. Special emphasis is put
on the nucleation phenomena and growth dynamics studied in detail
by in situ scanning tunnelling microscopy and high-resolution scanning
transmission electron microscopy. The morphology of the Bi<sub>2</sub>Te<sub>3</sub> surface and the structure of the Si(111)/Bi<sub>2</sub>Te<sub>3</sub> interface as well as the formation of threading dislocations
and crystal domains are studied at the atomic level. Our data indicate
that the film is formed via the nucleation of islands, which float
on the substrate; thus, the islands are only weakly bonded to the
substrate and rather mobile. Apparently, these floating islands are
able to arrange themselves by moving in the <i>x</i>–<i>y</i> direction to perfectly coalesce and form a continuous
film. The results present a crucial step toward understanding growth
and defect formation in this class of materials and thus pave the
avenue to a higher control over both their structural and electronic
properties, in order to study the electronic properties of the Dirac
surface states
Molecular Beam Epitaxy Growth of GaAs/InAs Core–Shell Nanowires and Fabrication of InAs Nanotubes
We present results about the growth of GaAs/InAs core–shell
nanowires (NWs) using molecular beam epitaxy. The core is grown via
the Ga droplet-assisted growth mechanism. For a homogeneous growth
of the InAs shell, the As<sub>4</sub> flux and substrate temperature
are critical. The shell growth starts with InAs islands along the
NW core, which increase in time and merge giving finally a continuous
and smooth layer. At the top of the NWs, a small part of the core
is free of InAs indicating a crystal phase selective growth. This
allows a precise measurement of the shell thickness and the fabrication
of InAs nanotubes by selective etching. The strain relaxation in the
shell occurs mainly via the formation of misfit dislocations and saturates
at ∼80%. Additionally, other types of defects are observed,
namely stacking faults transferred from the core or formed in the
shell, and threading dislocations
Amphoteric Nature of Sn in CdS Nanowires
High-quality CdS nanowires with uniform
Sn doping were synthesized
using a Sn-catalyzed chemical vapor deposition method. X-ray diffraction
and transmission electron microscopy demonstrate the single crystalline
wurtzite structure of the CdS/Sn nanowires. Both donor and acceptor
levels, which originate from the amphoteric nature of Sn in II–VI
semiconductors, are identified using low-temperature microphotoluminescence.
This self-compensation effect was cross examined by gate modulation
and temperature-dependent electrical transport measurement. They show
an overall n-type behavior with relatively low carrier concentration
and low carrier mobilities. Moreover, two different donor levels due
to intrinsic and extrinsic doping could be distinguished. They agree
well with both the electrical and optical data
Ranko Marinković in Czech translations
This work deals with the literary production of Croatian author Ranko Marinković and surveys primarily his publications released in Czech language. The biggest part presents two most important translations - the collection of short stories Ruce (The Hands) and the novel Kyklop (The Cyclops)