58,807 research outputs found
P/N InP homojunction solar cells by LPE and MOCVD techniques
P/N InP homojunction solar cells have been prepared by using both liquid phase epitaxy (LPE) and metallorganic chemical vapor deposition (MOCVD) growth techniques. A heavily doped p-In sub 0.53Ga sub 0.47As contacting layer was incorporated into the cell structure to improve the fill factor and to eliminate surface spiking at the front surface. The best conversion efficiencies (total area) obtained under AM 1 illumination are 14.2 percent for a LPE cell and 15.4 percent for a MOCVD cell
Variability of the NGC 1333 IRAS 4A Outflow: Molecular Hydrogen and Silicon Monoxide Images
The NGC 1333 region was observed in the H2 1-0 S(1) line. The H2 images cover
a 5' x 7' region around IRAS 4. Numerous H2 emission features were detected.
The northeast-southwest bipolar outflow driven by IRAS 4A was studied by
combining the H2 images with SiO maps published previously. The SiO-H2 outflows
are continuous on the southwestern side but show a gap on the northeastern
side. The southwestern outflow lobe curves smoothly, and the position angle
increases with the distance from the driving source. The base and the outer tip
of the northeastern outflow lobe are located at positions opposite to the
corresponding parts of the southwestern lobe. This point-symmetry suggests that
the outflow axis may be drifting or precessing clockwise in the plane of the
sky and that the cause of the axis drift may be intrinsic to the outflow
engine. The axis drift model is supported by the asymmetric lateral intensity
profile of the SiO outflow. The axis drift rate is about 0.011 deg yr-1. The
middle part of the northeastern outflow does not exactly follow the point
symmetry because of the superposition of two different kinds of directional
variability: the axis drift of the driving source and the deflection by a dense
core. The axis drift model provides a good explanation for the large deflection
angle of the northeastern outflow. Other H2 emission features around the IRAS 4
region are discussed briefly. Some of them are newly found outflows, and some
are associated with outflows already known before
Ammonia Imaging of the Disks in the NGC 1333 IRAS 4A Protobinary System
The NGC 1333 IRAS 4A protobinary was observed in the ammonia (2, 2) and (3,
3) lines and in the 1.3 cm continuum with a high resolution (about 1.0 arcsec).
The ammonia maps show two compact sources, one for each protostar, and they are
probably protostellar accretion disks. The disk associated with IRAS 4A2 is
seen nearly edge-on and shows an indication of rotation. The A2 disk is
brighter in the ammonia lines but dimmer in the dust continuum than its sibling
disk, with the ammonia-to-dust flux ratios different by about an order of
magnitude. This difference suggests that the twin disks have surprisingly
dissimilar characters, one gas-rich and the other dusty. The A2 disk may be
unusually active or hot, as indicated by its association with water vapor
masers. The existence of two very dissimilar disks in a binary system suggests
that the formation process of multiple systems has a controlling agent lacking
in the isolated star formation process and that stars belonging to a multiple
system do not necessarily evolve in phase with each other
Dynamics of Vortex Core Switching in Ferromagnetic Nanodisks
Dynamics of magnetic vortex core switching in nanometer-scale permalloy disk,
having a single vortex ground state, was investigated by micromagnetic
modeling. When an in-plane magnetic field pulse with an appropriate strength
and duration is applied to the vortex structure, additional two vortices, i.e.,
a circular- and an anti-vortex, are created near the original vortex core.
Sequentially, the vortex-antivortex pair annihilates. A spin wave is created at
the annihilation point and propagated through the entire element; the relaxed
state for the system is the single vortex state with a switched vortex core.Comment: to appear in Appl. Phys. Let
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