The impact of radiation damage on the device performance of 4H-SiC metal Schottky field effect transistors, which are irradiated at room temperature with 2-MeV electrons, is studied. No performance ...degradation is observed by
1
×
10
15
e
/
cm
2
, while a slight increase of the linear drain current together with a decrease of the threshold voltage are noticed for
1
×
10
16
e
/
cm
2
. The degradation for low electron fluence is mainly attributed to the radiation-induced decrease of the Schottky barrier height at the gate contact. For exposures over
1
×
10
16
e
/
cm
2
, the drain current and transconductance decrease. The maximum transconductance for
1
×
10
17
e
/
cm
2
is only 18% of the value before irradiation. Although no electron capture levels are observed before irradiation, three electron capture levels (
E
1
–
E
3
) are induced after irradiation. The observed increase of the channel resistance is due to the induced lattice defects creating electron traps.
As highly efficient organic sensitizers for dye-sensitized solar cells, a series of novel oligoene dyes which have different lengths of methine units, cyano groups and/or carboxylic groups as the ...electron acceptor units, and amino groups as the electron donor units was designed and synthesized. The bathochromic shift of the absorption spectrum was achieved by expansion of the π-conjugated system by increasing the number of methine units and by introduction of both electron-withdrawing and -accepting groups, which induced charge-transfer-type absorption character. Redox potential of the dyes was also controlled by the substitution of the functional groups. Dye-sensitized solar cells (DSCs) based on the oligoene dyes showed excellent response of incident photon to current conversion efficiency (>80%), leading to good photovoltaic performances up to 6.6% under 1 sun irradiation conditions. Femtosecond transient absorption spectroscopy in the mid-IR region revealed the very fast electron injection from the excited states of the oligoene dyes to the conduction band of TiO2. The molecular design of oligoene dye is reliable for developing novel organic sensitizers for use in dye-sensitized solar cells.
The PHENIX collaboration presents first measurements of low-momentum (0.4<p_{T}<3 GeV/c) direct-photon yields from Au+Au collisions at sqrts_{NN}=39 and 62.4 GeV. For both beam energies the ...direct-photon yields are substantially enhanced with respect to expectations from prompt processes, similar to the yields observed in Au+Au collisions at sqrts_{NN}=200. Analyzing the photon yield as a function of the experimental observable dN_{ch}/dη reveals that the low-momentum (>1 GeV/c) direct-photon yield dN_{γ}^{dir}/dη is a smooth function of dN_{ch}/dη and can be well described as proportional to (dN_{ch}/dη)^{α} with α≈1.25. This scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and the Large Hadron Collider, for centrality selected samples, as well as for different A+A collision systems. At a given beam energy, the scaling also holds for high p_{T} (>5 GeV/c), but when results from different collision energies are compared, an additional sqrts_{NN}-dependent multiplicative factor is needed to describe the integrated-direct-photon yield.
Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements ...from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (
p
T
), elliptic flow, two-particle correlations, nonstatistical fluctuations, and suppression of particle production at high
p
T
. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.
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