8 research outputs found
Sample characteristics by condition.
<p>Doctors included consultant and staff grade psychiatrists.</p
The Distribution of Confidence Ratings by Profession and Gender.
<p>The Distribution of Confidence Ratings by Profession and Gender.</p
āSuicideā and āNon-suicideā responses by condition.
<p>āSuicideā and āNon-suicideā responses by condition.</p
Confidence ratings by condition and by response.
<p>Confidence ratings by condition and by response.</p
āSuicideā responses for male and female participants by professional group.
<p>āSuicideā responses for male and female participants by professional group.</p
Quantitative Phase-Change Thermodynamics and Metastability of Perovskite-Phase Cesium Lead Iodide
The
perovskite phase of cesium lead iodide (Ī±-CsPbI<sub>3</sub> or
āblackā phase) possesses favorable optoelectronic
properties for photovoltaic applications. However, the stable phase
at room temperature is a nonfunctional āyellowā phase
(Ī“-CsPbI<sub>3</sub>). Black-phase polycrystalline thin films
are synthesized above 330 Ā°C and rapidly quenched to room temperature,
retaining their phase in a metastable state. Using differential scanning
calorimetry, it is shown herein that the metastable state is maintained
in the absence of moisture, up to a temperature of 100 Ā°C, and
a reversible phase-change enthalpy of 14.2 (Ā±0.5) kJ/mol is observed.
The presence of atmospheric moisture hastens the black-to-yellow conversion
kinetics without significantly changing the enthalpy of the transition,
indicating a catalytic effect, rather than a change in equilibrium
due to water adduct formation. These results delineate the conditions
for trapping the desired phase and highlight the significant magnitude
of the entropic stabilization of this phase
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Surface Chemically Switchable Ultraviolet Luminescence from Interfacial Two-Dimensional Electron Gas
We
report intense, narrow line-width, surface chemisorption-activated
and reversible ultraviolet (UV) photoluminescence from radiative recombination
of the two-dimensional electron gas (2DEG) with photoexcited holes
at LaAlO<sub>3</sub>/SrTiO<sub>3</sub>. The switchable luminescence
arises from an electron transfer-driven modification of the electronic
structure via H-chemisorption onto the AlO<sub>2</sub>-terminated
surface of LaAlO<sub>3</sub>, at least 2 nm away from the interface.
The control of the onset of emission and its intensity are functionalities
that go beyond the luminescence of compound semiconductor quantum
wells. Connections between reversible chemisorption, fast electron
transfer, and quantum-well luminescence suggest a new model for surface
chemically reconfigurable solid-state UV optoelectronics and molecular
sensing
BaTiO<sub>3</sub> Thin Films from Atomic Layer Deposition: A Superlattice Approach
A superlattice
approach for the atomic layer deposition of polycrystalline
BaTiO<sub>3</sub> thin films is presented as an example for an effective
route to produce high-quality complex oxide films with excellent thickness
and compositional control. This method effectively mitigates any undesirable
reactions between the different precursors and allows an individual
optimization of the reaction conditions for the BaāO and the
TiāO subcycles. By growth of nanometer thick alternating BaĀ(OH)<sub>2</sub> and TiO<sub>2</sub> layers, the advantages of binary oxide
atomic layer deposition are transferred into the synthesis of ternary
compounds, permitting extremely high control of the cation ratio and
superior uniformity. Whereas the BaĀ(OH)<sub>2</sub> layers are partially
crystalline after the deposition, the TiO<sub>2</sub> layers remain
mostly amorphous. The layers react to polycrystalline, polymorph BaTiO<sub>3</sub> above 500 Ā°C, releasing H<sub>2</sub>O. This solid-state
reaction is accompanied by an abrupt decrease in film thickness. Transmission
electron microscopy and Raman spectroscopy reveal the presence of
hexagonal BaTiO<sub>3</sub> in addition to the perovskite phase in
the annealed films. The microstructure with relatively small grains
of ā¼70 Ć
and different phases is a direct consequence
of the abrupt formation reaction. The electrical properties transition
from the initially highly insulating dielectric semiamorphous superlattice
into a polycrystalline BaTiO<sub>3</sub> thin film with a dielectric
constant of 117 and a dielectric loss of 0.001 at 1 MHz after annealing
at 600 Ā°C in air, which, together with the suppression of ferroelectricity
at room temperature, are very appealing properties for voltage tunable
devices