7 research outputs found
1919 in dynamic East Asia: March First and May Fourth as a starting point for revolution
Al<sub>2</sub>O<sub>3</sub> Passivation Effect in HfO<sub>2</sub>·Al<sub>2</sub>O<sub>3</sub> Laminate Structures Grown on InP Substrates
The
passivation effect of an Al<sub>2</sub>O<sub>3</sub> layer on the
electrical properties was investigated in HfO<sub>2</sub>âAl<sub>2</sub>O<sub>3</sub> laminate structures grown on indium phosphide
(InP) substrate by atomic-layer deposition. The chemical state obtained
using high-resolution X-ray photoelectron spectroscopy showed that
interfacial reactions were dependent on the presence of the Al<sub>2</sub>O<sub>3</sub> passivation layer and its sequence in the HfO<sub>2</sub>âAl<sub>2</sub>O<sub>3</sub> laminate structures. Because
of the interfacial reaction, the Al<sub>2</sub>O<sub>3</sub>/HfO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> structure showed the best electrical
characteristics. The top Al<sub>2</sub>O<sub>3</sub> layer suppressed
the interdiffusion of oxidizing species into the HfO<sub>2</sub> films,
whereas the bottom Al<sub>2</sub>O<sub>3</sub> layer blocked the outdiffusion
of In and P atoms. As a result, the formation of InâO bonds
was more effectively suppressed in the Al<sub>2</sub>O<sub>3</sub>/HfO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub>/InP structure than that
in the HfO<sub>2</sub>-on-InP system. Moreover, conductance data revealed
that the Al<sub>2</sub>O<sub>3</sub> layer on InP reduces the midgap
traps to 2.6 Ă 10<sup>12</sup> eV<sup>â1</sup> cm<sup>â2</sup> (compared to that of HfO<sub>2</sub>/InP, that is,
5.4 Ă 10<sup>12</sup> eV<sup>â1</sup> cm<sup>â2</sup>). The suppression of gap states caused by the outdiffusion of In
atoms significantly controls the degradation of capacitors caused
by leakage current through the stacked oxide layers
Perovskite Nanocrystals Protected by Hermetically Sealing for Highly Bright and Stable DeepâBlue LightâEmitting Diodes
Abstract Metalâhalide perovskite nanocrystals (NCs) have emerged as suitable lightâemitting materials for lightâemitting diodes (LEDs) and other practical applications. However, LEDs with perovskite NCs undergo environmentâinduced and ionâmigrationâinduced structural degradation during operation; therefore, novel NC design concepts, such as hermetic sealing of the perovskite NCs, are required. Thus far, viable synthetic conditions to form a robust and hermetic semiconducting shell on perovskite NCs have been rarely reported for LED applications because of the difficulties in the delicate engineering of encapsulation techniques. Herein, a highly bright and durable deepâblue perovskite LED (PeLED) formed by hermetically sealing perovskite NCs with epitaxial ZnS shells is reported. This shell protects the perovskite NCs from the environment, facilitates charge injection/transport, and effectively suppresses interparticle ion migration during the LED operation, resulting in exceptional brightness (2916Â cd mâ2) at 451Â nm and a high external quantum efficiency of 1.32%. Furthermore, even in the unencapsulated state, the LED shows a long operational lifetime (T50) of 1192 s (â20Â min) in the air. These results demonstrate that the epitaxial and hermetic encapsulation of perovskite NCs is a powerful strategy for fabricating highâperformance deepâblueâemitting PeLEDs
Structural and Electrical Properties of EOT HfO<sub>2</sub> (<1 nm) Grown on InAs by Atomic Layer Deposition and Its Thermal Stability
We report on changes in the structural,
interfacial, and electrical characteristics of sub-1 nm equivalent
oxide thickness (EOT) HfO<sub>2</sub> grown on InAs by atomic layer
deposition. When the HfO<sub>2</sub> film was deposited on an InAs
substrate at a temperature of 300 °C, the HfO<sub>2</sub> was
in an amorphous phase with an sharp interface, an EOT of 0.9 nm, and
low preexisting interfacial defect states. During post deposition
annealing (PDA) at 600 °C, the HfO<sub>2</sub> was transformed
from an amorphous to a single crystalline orthorhombic phase, which
minimizes the interfacial lattice mismatch below 0.8%. Accordingly,
the HfO<sub>2</sub> dielectric after the PDA had a dielectric constant
of âŒ24 because of the permittivity of the well-ordered orthorhombic
HfO<sub>2</sub> structure. Moreover, border traps were reduced by
half than the as-grown sample due to a reduction in bulk defects in
HfO<sub>2</sub> dielectric during the PDA. However, in terms of other
electrical properties, the characteristics of the PDA-treated sample
were degraded compared to the as-grown sample, with EOT values of
1.0 nm and larger interfacial defect states (D<sub>it</sub>) above
1 Ă 10<sup>14</sup> cm<sup>â2</sup> eV<sup>â1</sup>. X-ray photoelectron spectroscopy data indicated that the diffusion
of In atoms from the InAs substrate into the HfO<sub>2</sub> dielectric
during the PDA at 600 °C resulted in the development of substantial
midgap states