8 research outputs found
X-ray Nanodiffraction on a Single SiGe Quantum Dot inside a Functioning Field-Effect Transistor
For advanced electronic, optoelectronic, or mechanical nanoscale devices a detailed understanding of their structural properties and in particular the strain state within their active region is of utmost importance. We demonstrate that X-ray nanodiffraction represents an excellent tool to investigate the internal structure of such devices in a nondestructive way by using a focused synchotron X-ray beam with a diameter of 400 nm. We show results on the strain fields in and around a single SiGe island, which serves as stressor for the Si-channel in a fully functioning Si-metal-oxide semiconductor field-effect transistor
Crystal Phase Selective Growth in GaAs/InAs CoreāShell Nanowires
We present a novel type of coreāshell
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>ā<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 CoreāShell Nanowires and Fabrication of InAs Nanotubes
We present results about the growth of GaAs/InAs coreāshell
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 ā¼80%. Additionally, other types of defects are observed,
namely stacking faults transferred from the core or formed in the
shell, and threading dislocations
Thermal expansion and temperature dependence of Raman modes in epitaxial layers of Ge and Ge1āxSnx
Extreme ultraviolet interference lithography at the Paul Scherrer Institut
Auzelyte V, Dais C, Farquet P, et al. Extreme ultraviolet interference lithography at the Paul Scherrer Institut. JOURNAL OF MICRO-NANOLITHOGRAPHY MEMS AND MOEMS. 2009;8(2):021204.We review the performance and applications of an extreme ultraviolet interference lithography (EUV-IL) system built at the Swiss Light Source of the Paul Scherrer Institut (Villigen, Switzerland). The interferometer uses fully coherent radiation from an undulator source. 1-D (line/space) and 2-D (dot/hole arrays) patterns are obtained with a transmission-diffraction-grating type of interferometer. Features with sizes in the range from one micrometer down to the 10-nm scale can be printed in a variety of resists. The highest resolution of 11-nm half-pitch line/space patterns obtained with this method represents a current record for photon based lithography. Thanks to the excellent performance of the system in terms of pattern resolution, uniformity, size of the patterned area, and the throughput, the system has been used in numerous applications. Here we demonstrate the versatility and effectiveness of this emerging nanolithography method through a review of some of the applications, namely, fabrication of metallic and magnetic nanodevice components, self-assembly of Si/Ge quantum dots, chemical patterning of self-assembled monolayers (SAM), and radiation grafting of polymers. (c) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3116559
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 IIāVI
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 MarinkoviÄ in Czech translations
This work deals with the literary production of Croatian author Ranko MarinkoviÄ 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)