Experimental verification of optical modulation with external stress has not been easily available in flexible systems. Here, we intentionally induced extra stress in wide band gap ZnO thin films by a unique prestress-driven deposition processing that utilizes a stretching mode. The stretching mode provides homogeneous but biaxial stresses in the hexagonal wurtzite structure, leading to the extension of the c-axis and the contraction of the a-axis. As a result, the reduction of the optical band gap by ∼150 meV was observed for the strain of ∼4.87%. The band gap narrowing was found to occur from the respective downward and upward shifts of the conduction band minimum and valence band maximum under the applied stress. The experimental evidence of optical modulations was supported by the theoretical calculations using density functional theory. The reduced strong interactions between Zn d and O p orbitals were assumed to be responsible for the band gap narrowing.
There
have been extensive efforts to develop competitive electrocatalysts
using carbon black (CB) supports for high-performance proton-exchange
membrane fuel cells with less usage of Pt. Herein, we propose a very
promising electrocatalyst architecture based on the three-dimensional
Pt/indium tin oxide (ITO)/CB support structure which was enabled by
a nonconventional deposition process ensuring very uniform impregnation
of Pt and ITO nanoparticles into the CB network. The unusual scales
of the Pt (∼1.9 nm) and ITO (∼5.6 nm) nanoparticles
were directly related to unexpectedly better performance of the electrocatalytic
activities. As a highlight, the electrochemical surface area of the
electrocatalyst was maintained very well after the 3000 cycle-accelerated
durability evaluation by demonstrating an excellent retention of ∼74.9%.
Particularly, the CO tolerance exhibited a low value of ∼0.68
V as the absorption current peak, compared to ∼0.79 V for a
commercial Pt/CB catalyst containing twice more Pt.
The requirements of low power consumption and fast operation have necessitated the development of thin film transistors (TFTs) with exploration of new dielectric materials. Here, the unprecedented integration of high‐κ dielectric CaCu3Ti4O12 is reported, yielding significant enhancements in the performance of amorphous InGaZnO TFTs. Using a multilayer structured amorphous Al2O3/CaCu3Ti4O12/Al2O3 dielectric configuration, the performance of the transistors is greatly improved as highlighted with high saturation mobility (>10 cm2 Vs−1), high on/off current ratio (3.8 × 107), low threshold voltage (≈0.51 V), and low subthreshold swing (≈0.45 V decade−1). The balanced performance enhancements are attributed to the lower density of interfacial/bulk trap states and sufficient band offsets.
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