257 research outputs found
Local growth of CuInSe2 micro solar cells for concentrator application
A procedure to fabricate CuInSe2 CISe micro absorbers and solar cells for concentrator applications is presented. The micro absorbers are developed from indium precursor islands, which are deposited on a molybdenum coated glass substrate back contact , followed by deposition of copper on top and subsequent selenization as well as selective etching of copper selenides. In order to compare the properties of the locally grown absorbers to those of conventional large area CISe films, we systematically examine the compositional and morphological homogeneity of the micro absorbers and carry out photoluminescence measurements. Preliminary devices for micro concentrator solar cell applications are fabricated by optimizing the copper to indium ratio and the size of the indium precursor islands. The resulting micro solar cells provide a characteristic I V curve under standard illumination conditions 1 su
Growth and shape of indium islands on molybdenum at micro-roughened spots created by femtosecond laser pulses
Indium islands on molybdenum coated glass can be grown in ordered arrays by surface structuring using a femtosecond laser. The effect of varying the molybdenum coated glass substrate temperature and the indium deposition rate on island areal density, volume and geometry is investigated and evaluated in a physical vapor deposition (PVD) process. The joined impact of growth conditions and spacing of the femtosecond laser structured spots on the arrangement and morphology of indium islands is demonstrated. The results yield a deeper understanding of the island growth and its precise adjustment to industrial requirements, which is indispensable for a technological application of such structures at a high throughput, for instance as precursors for the preparation of Cu(In,Ga)Se2 micro concentrator solar cells
Regularly arranged indium islands on glass/molybdenum substrates upon femtosecond laser and physical vapor deposition processing
A bottom-up approach is presented for the production of arrays of indium
islands on a molybdenum layer on glass, which can serve as micro-sized
precursors for indium compounds such as copper-indium-gallium-diselenide used
in photovoltaics. Femtosecond laser ablation of glass and a subsequent
deposition of a molybdenumfilm or direct laser processing of the
molybdenumfilm both allow the preferential nucleation and growth of indium
islands at the predefined locations in a following indium-based physical vapor
deposition(PVD) process. A proper choice of laser and deposition parameters
ensures the controlled growth of indium islands exclusively at the laser
ablated spots. Based on a statistical analysis, these results are compared to
the non-structured molybdenumsurface, leading to randomly grown indium islands
after PVD
Quantum Theory in Accelerated Frames of Reference
The observational basis of quantum theory in accelerated systems is studied.
The extension of Lorentz invariance to accelerated systems via the hypothesis
of locality is discussed and the limitations of this hypothesis are pointed
out. The nonlocal theory of accelerated observers is briefly described.
Moreover, the main observational aspects of Dirac's equation in noninertial
frames of reference are presented. The Galilean invariance of nonrelativistic
quantum mechanics and the mass superselection rule are examined in the light of
the invariance of physical laws under inhomogeneous Lorentz transformations.Comment: 25 pages, no figures, contribution to Springer Lecture Notes in
Physics (Proc. SR 2005, Potsdam, Germany, February 13 - 18, 2005
Lithium atom interferometer using laser diffraction : description and experiments
We have built and operated an atom interferometer of the Mach-Zehnder type.
The atomic wave is a supersonic beam of lithium seeded in argon and the mirrors
and beam-splitters for the atomic wave are based on elastic Bragg diffraction
on laser standing waves at 671 nm. We give here a detailed description of our
experimental setup and of the procedures used to align its components. We then
present experimental signals, exhibiting atomic interference effects with a
very high visibility, up to 84.5 %. We describe a series of experiments testing
the sensitivity of the fringe visibility to the main alignment defects and to
the magnetic field gradient.Comment: 8 avril 200
Spin-gravity coupling and gravity-induced quantum phases
External gravitational fields induce phase factors in the wave functions of
particles. The phases are exact to first order in the background gravitational
field, are manifestly covariant and gauge invariant and provide a useful tool
for the study of spin-gravity coupling and of the optics of particles in
gravitational or inertial fields. We discuss the role that spin-gravity
coupling plays in particular problems.Comment: 18 pages, 1 figur
Quantum systems in weak gravitational fields
Fully covariant wave equations predict the existence of a class of
inertial-gravitational effects that can be tested experimentally. In these
equations inertia and gravity appear as external classical fields, but, by
conforming to general relativity, provide very valuable information on how
Einstein's views carry through in the world of the quantum.Comment: 22 pages. To be published in Proceedings of the 17th Course of the
International School of Cosmology and Gravitation "Advances in the interplay
between quantum and gravity physics" edited by V. De Sabbata and A.
Zheltukhin, Kluwer Academic Publishers, Dordrech
Exoplanet Imaging Data Challenge, phase II: Characterization of exoplanet signals in high-contrast images
Today, there exists a wide variety of algorithms dedicated to high-contrast
imaging, especially for the detection and characterisation of exoplanet
signals. These algorithms are tailored to address the very high contrast
between the exoplanet signal(s), which can be more than two orders of magnitude
fainter than the bright starlight residuals in coronagraphic images. The
starlight residuals are inhomogeneously distributed and follow various
timescales that depend on the observing conditions and on the target star
brightness. Disentangling the exoplanet signals within the starlight residuals
is therefore challenging, and new post-processing algorithms are striving to
achieve more accurate astrophysical results. The Exoplanet Imaging Data
Challenge is a community-wide effort to develop, compare and evaluate
algorithms using a set of benchmark high-contrast imaging datasets. After a
first phase ran in 2020 and focused on the detection capabilities of existing
algorithms, the focus of this ongoing second phase is to compare the
characterisation capabilities of state-of-the-art techniques. The
characterisation of planetary companions is two-fold: the astrometry (estimated
position with respect to the host star) and spectrophotometry (estimated
contrast with respect to the host star, as a function of wavelength). The goal
of this second phase is to offer a platform for the community to benchmark
techniques in a fair, homogeneous and robust way, and to foster collaborations.Comment: Submitted to SPIE Astronomical Telescopes + Instrumentation 2022,
Adaptive Optics Systems VIII, Paper 12185-
Atom Interferometers
Interference with atomic and molecular matter waves is a rich branch of
atomic physics and quantum optics. It started with atom diffraction from
crystal surfaces and the separated oscillatory fields technique used in atomic
clocks. Atom interferometry is now reaching maturity as a powerful art with
many applications in modern science. In this review we first describe the basic
tools for coherent atom optics including diffraction by nanostructures and
laser light, three-grating interferometers, and double wells on AtomChips. Then
we review scientific advances in a broad range of fields that have resulted
from the application of atom interferometers. These are grouped in three
categories: (1) fundamental quantum science, (2) precision metrology and (3)
atomic and molecular physics. Although some experiments with Bose Einstein
condensates are included, the focus of the review is on linear matter wave
optics, i.e. phenomena where each single atom interferes with itself.Comment: submitted to Reviews of Modern Physic
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