1,721,012 research outputs found
Optical characterization of Al(X)Ga(1-x)Sb/GaSb epitaxial heterostructures
No full textThe complex refractive index n+ik and the dielectric function e1+ie2 at room temperature
of AlxGa12xSb films with 0<x<0.5, grown by molecular beam epitaxy on a GaSb substrate, were
determined from 0.02 to 6 eV by using the complementary data from fast Fourier transform
far-infrared, dispersive, and ellipsometric spectrometry. The effect of the native oxide was
accounted for and the self-consistency of the optical functions was checked in the framework of the
Kramers–Kronig causality relations. In the restrahlen region the dielectric function was well fitted
by classical Lorentz oscillators; in the transparent region below the fundamental gap E0, the
refractive index was modeled by a Sellmeier dispersion relation, and in the interband region the
dielectric function near the critical points was analyzed through standard line shapes. Interpolating
the fitting parameters or the interband dielectric spectra, it was possible to obtain the optical
functions for any concentration x between 0.0 and 0.5
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
PHOTOREFLECTANCE VERSUS PHOTOLUMINESCENCE IN STRAIN INDUCED QUANTUM WELL WIRES
No full textPhotoreflectance vs photoluminescence measurements of stress-induced quantum wires, obtained by patterning an InGaAs layer pseudomorphic grown on a GaAs well in wire-shaped stressors, are presented and compared. An excellent agreement was found between the experimental results obtained with the two techniques about the lateral confinement of the carriers and evidence is given at room temperature of quantization in two directions by means of photoreflectance
Low temperature thermoreflectance of AlxGa1-xAs/GaAs quantum wells
No full textReflectance (R) and thermoreflectance (TR) of quantum well structures grown by MBE have been investigated at low temperature (30 K) in order to demonstrate the capabilities of TR to study quantum confined systems. Our results show that low temperature TR is a simple and yet very efficient technique which provides large signals (ΔR/R>103), also in the case of reduced-dimensionality systems. We also show that TR can extract spectroscopic information from relatively high background reflectance and that it can be used to study transitions between subbands higher than the fundamental ones. The TR modulation mechanisms are discussed and the TR and R lineshapes are compared. The first-derivative nature of TR allows for a straightforward and reliable comparison between experiment and theory; this feature may have interesting applications in the study of QWs and SLs, where interference effects from the multilayer structure may complicate the analysis of the spectra
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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