2,572 research outputs found
Interview with Mark Gilmore
Mark Gilmore talks about local outdoor activities.https://digital.kenyon.edu/lak_interviews/1018/thumbnail.jp
Fabrication of minority-carrier-limited n-Si/insulator/metal diodes
A photoelectrochemical anodization technique has been used to fabricate n-Si/insulator/metal (MIS) diodes with improved electrical properties. MIS structures fabricated with Au have provided the first experimental observation of a solid-state n-Si surface barrier device whose open circuit voltage Voc is controlled by minority-carrier bulk diffusion/recombination processes. For these diodes, variation of the minority-carrier diffusion length and majority-carrier dopant density produced changes in Voc that were in accord with bulk diffusion/recombination theory. Additionally, the variation in Voc in response to changes in the work function of the metal overlayer indicated that these MIS devices were not subject to the Fermi level pinning restrictions observed for n-Si Schottky structures. X-ray photoelectron spectroscopic characterization of the anodically grown insulator indicated 8.2±0.9 Å of a strained SiO2 layer as the interfacial insulator resulting from the photoanodization process
Multi-chord fiber-coupled interferometer with a long coherence length laser
This paper describes a 561 nm laser heterodyne interferometer that provides
time-resolved measurements of line-integrated plasma electron density within
the range of 10^15-10^18 cm^(-2). Such plasmas are produced by railguns on the
Plasma Liner Experiment (PLX), which aims to produce \mu s-, cm-, and
Mbar-scale plasmas through the merging of thirty plasma jets in a spherically
convergent geometry. A long coherence length, 320 mW laser allows for a strong,
sub-fringe phase-shift signal without the need for closely-matched probe and
reference path lengths. Thus only one reference path is required for all eight
probe paths, and an individual probe chord can be altered without altering the
reference or other probe path lengths. Fiber-optic decoupling of the probe
chord optics on the vacuum chamber from the rest of the system allows the probe
paths to be easily altered to focus on different spatial regions of the plasma.
We demonstrate that sub-fringe resolution capability allows the interferometer
to operate down to line-integrated densities of order 10^15 cm^(-2).Comment: submitted to Rev. Sci. Instrum. (2011
The low-mass IMF - deep star counts in the dSph galaxy Ursa Minor
We present a new study of deep star counts in the Local Group dwarf
spheroidal (dSph) in Ursa Minor. Both the luminosity function (LF) and the
colour-magnitude diagram (CMD) of the unevolved stars are compared with the LF
and CMD of the old, metal-poor globular cluster M92. The main sequence
locations and turn-offs are identical within the errors. Since we know from the
brighter evolved stars that the metallicities for these two disparate systems
are the same this implies that they also have equal ages. A direct comparison
of faint LFs is then equivalent to comparison of the low-mass stellar Initial
Mass Functions (IMF). We find that their LFs are identical within the
mass-range covered (~0.35 - 0.8 M_sun). The Ursa Minor dSph has one of the
highest apparent M/L ratios known in the Local Group, and is an extremely low
surface brightness external galaxy. M92 is a typical high surface brightness
globular cluster, with no apparent dark matter. These results lead to the
conclusion that the low-mass stellar IMF in systems that formed at high
redshift is independent of environment. Indeed, it is consistent with the
low-mass IMF in star-forming regions today.Comment: To appear in the proceedings of "Modes of Star Formation and the
Origin of Field Populations", ASP Conf Ser, eds E Grebel & W Brandne
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