Design and synthesis of super-nanostructures is one of the key and prominent topics in nanotechnology. Here we propose a novel methodology for synthesizing complex hierarchical superstructures using sacrificial templates composed of ordered two-dimensional (2D) nanostructures through lattice-directed topotactic transformations. The fabricated superstructures are nested 2D orthogonal Bi(2)S(3) networks composed of nanorods. Further investigation indicates that the lattice matching between the product and sacrificial template is the dominant mechanism for the formation of the superstructures, which agrees well with the simulation results based on an anisotropic nucleation and growth analysis. Our approach may provide a promising way toward a lattice-directed nonlithographic nanofabrication technique for making functional porous nanoarchitectures and electronic devices.
We have reported the synthesis of superstructured nanonetworks of BiOCl and nested nanonetworks of Bi(2)S(3) in a series of lattice-directed topotactic transformations [C. F. Guo et al. J. Am. Chem. Soc. 2011, 138, 8211-8215]. Here we extend the transformations to a much broader system including ordered nanowall networks of BiOCl, BiOBr, Bi(2)O(2)CO(3), β-Bi(2)O(3), and Bi(2)S(3), as well as nested self-similar networks of Bi(2)S(3) and amorphous BiO(x). We suggest even more superstructured networks and nested self-similar networks of bismuth compounds with a lattice parameter of ~2(n/2) × 3.9 Å (n = 0, 1, 2, 3, 4), might also be obtained. The superstructured networks and nested networks are novel architectures that may find applications in electronic devices, sensors, filters, and photocatalysts.
Augmented reality
and visual reality (AR and VR) microdisplays
require micro light emitting diodes (μLEDs) with an ultrasmall
dimension (≤5 μm), high external quantum efficiency (EQE),
and narrow spectral line width. Unfortunately, dry etching which is
the most crucial step for the fabrication of μLEDs in current
approaches introduces severe damages, which seem to become an insurmountable
challenge for achieving ultrasmall μLEDs with high EQE. Furthermore,
it is well-known that μLEDs which require InGaN layers as an
emitting region naturally exhibit significantly broad spectral line
width, which becomes increasingly severe toward long wavelengths such
as green. In this paper, we have reported a combination of our selective
overgrowth approach developed very recently and epitaxial lattice-matched
distributed Bragg reflectors (DBRs) embedded in order to address all
these fundamental issues. As a result, our μLEDs with a diameter
of 3.6 μm and an interpitch of 2 μm exhibit an ultrahigh
EQE of 9% at ∼500 nm. More importantly, the spectral line width
of our μLEDs has been significantly reduced down to 25 nm, the
narrowest value reported so far for III-nitride green μLEDs.
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