92 research outputs found
Growth Mechanism of Self-Catalyzed Group III−V Nanowires
Group III-V nanowires offer the exciting possibility of epitaxial growth on a wide variety of substrates, most importantly silicon. To ensure compatibility with Si technology, catalyst-free growth schemes are of particular relevance, to avoid impurities from the catalysts. While this type of growth is well-documented and some aspects are described, no detailed understanding of the nucleation and the growth mechanism has been developed. By combining a series of growth experiments using metal-organic vapor phase epitaxy, as well as detailed in situ surface imaging and spectroscopy, we gain deeper insight into nucleation and growth of self-seeded III-V nanowires. By this mechanism most work available in literature concerning this field can be described
<雑録>餘剩價値ノ原理
Within the quest for direct band-gap group IV materials, strain engineering in germanium is one promising route. We present a study of the strain distribution in single, suspended germanium nanowires using nanofocused synchrotron radiation. Evaluating the probed Bragg reflection for different illumination positions along the nanowire length results in corresponding strain components as well as the nanowire's tilting and bending. By using these findings we determined the complete strain state with the help of finite element modelling. The resulting information provides us with the possibility of evaluating the validity of the strain investigations following from Raman scattering experiments which are based on the assumption of purely uniaxial strain
Strain-Tuning of the Optical Properties of Semiconductor Nanomaterials by Integration onto Piezoelectric Actuators
The tailoring of the physical properties of semiconductor nanomaterials by
strain has been gaining increasing attention over the last years for a wide
range of applications such as electronics, optoelectronics and photonics. The
ability to introduce deliberate strain fields with controlled magnitude and in
a reversible manner is essential for fundamental studies of novel materials and
may lead to the realization of advanced multi-functional devices. A prominent
approach consists in the integration of active nanomaterials, in thin epitaxial
films or embedded within carrier nanomembranes, onto
Pb(Mg1/3Nb2/3)O3-PbTiO3-based piezoelectric actuators, which convert electrical
signals into mechanical deformation (strain). In this review, we mainly focus
on recent advances in strain-tunable properties of self-assembled InAs quantum
dots embedded in semiconductor nanomembranes and photonic structures.
Additionally, recent works on other nanomaterials like rare-earth and metal-ion
doped thin films, graphene and MoS2 or WSe2 semiconductor two-dimensional
materials are also reviewed. For the sake of completeness, a comprehensive
comparison between different procedures employed throughout the literature to
fabricate such hybrid piezoelectric-semiconductor devices is presented. Very
recently, a novel class of micro-machined piezoelectric actuators have been
demonstrated for a full control of in-plane stress fields in nanomembranes,
which enables producing energy-tunable sources of polarization-entangled
photons in arbitrary quantum dots. Future research directions and prospects are
discussed.Comment: review manuscript, 78 pages, 27 figure
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
Scanning X-ray strain microscopy of inhomogeneously strained Ge micro-bridges
ISSN:0909-0495ISSN:1600-577
Binge and High-Intensity Drinking – Associations with Intravenous Alcohol Self-Administration and Underlying Risk Factors
Some styles of alcohol consumption are riskier than others. How the level and rate of alcohol exposure contribute to the increased risk of alcohol use disorder is unclear, but likely depends on the alcohol concentration time course. We hypothesized that the brain is sensitive to the alcohol concentration rate of change and that people at greater risk would self-administer faster. We developed a novel intravenous alcohol self-administration paradigm to allow participants direct and reproducible control over how quickly their breath alcohol concentration changes. We used drinking intensity and the density of biological family history of alcohol dependence as proxies for risk. Thirty-five alcohol drinking participants aged 21-28 years provided analytical data from a single, intravenous alcohol self-administration session using our computer-assisted alcohol infusion system rate control paradigm. A shorter time to reach 80 mg/dl was associated with increasing multiples of the binge drinking definition (p = 0.004), which was in turn related to higher density of family history of alcoholism (FHD, p = 0.04). Rate-dependent changes in subjective response (intoxication and stimulation) were also associated with FHD (each p = 0.001). Subsequently, given the limited sample size and FHD range, associations between multiples of the binge drinking definition and FHD were replicated and extended in analyses of the Collaborative Study on the Genetics of Alcoholism database. The rate control paradigm models binge and high-intensity drinking in the laboratory and provides a novel way to examine the relationship between the pharmacokinetics and pharmacodynamics of alcohol and potentially the risk for the development of alcohol use disorders
Nanobeam X-ray scattering: probing matter at the nanoscale
A comprehensive overview of the possibilities and potential of X-ray scattering using nanofocused beams for probing matter at the nanoscale, including guidance on the design of nanobeam experiments. The monograph discusses various sources, including free electron lasers, synchrotron radiation and other portable and non-portable X-ray sources. For scientists using synchrotron radiation or students and scientists with a background in X-ray scattering methods in general
Nanobeam X-ray Scattering
International audienceA comprehensive overview of the possibilities and potential of X-ray scattering using nanofocused beams for probing matter at the nanoscale, including guidance on the design of nanobeam experiments. The monograph discusses various sources, including free electron lasers, synchrotron radiation and other portable and non-portable X-ray sources.For scientists using synchrotron radiation or students and scientists with a background in X-ray scattering methods in general
Au-Seeded Growth of Vertical and in-Plane III-V Nanowires on Graphite Substrates.
Graphene is promising as a transparent, flexible, and possibly cost-effective substrate for nanowire-based devices. We have investigated Au-seeded III-V nanowire growth with graphite as a model substrate. The highest yield of undoped vertical nanowires was found for InAs, but we also observed vertical nanowires for the InP, GaP, and GaAs materials. The yield of vertical nanowires for GaP and GaAs was strongly improved by supplying the p-dopant DEZn before nanowire growth but not by supplying H2S or HCl. In-plane GaAs and GaP nanowire growth exhibited an unexpected behavior, where the seed particles seemingly reflected on the side facets of other nanowires. These results pave the way for vertical and in-plane hybrid graphene- nanowire devices
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