11 research outputs found
In-plane Anisotropy of Quantum Transport in Artificial Two-dimensional Au Lattices
We
report an experimental observation and direct control of quantum
transport in artificial two-dimensional Au lattices. Combining the
advanced techniques of low-temperature deposition and newly developed
double-probe scanning tunneling spectroscopy, we display a two-dimensional
carrier transport and demonstrate a strong in-plane transport modulation
in the two-dimensional Au lattices. In well-ordered Au lattices, we
observe the carrier transport behavior manifesting as a band-like
feature with an energy gap. Furthermore, controlled structural modification
performed by constructing coupled āstadiumsā enables
a transition of system dynamics in the lattices, which in turn establishes
tunable resonant transport throughout a wide energy range. Our findings
open the possibility of the construction and transport engineering
of artificial lattices by the geometrical arrangement of scatterers
and quantum chaotic dynamics
Defect Suppression in AlN Epilayer Using Hierarchical Growth Units
Growing AlN layers
remains a significant challenge because it is
subject to a large volume fraction of grain boundaries. In this study,
the nature and formation of the AlN growth mechanism is examined by
ab initio simulations and experimental demonstration. The calculated
formation enthalpies of the constituent elements, including the Al/N
atom, AlāN molecule, and AlāN<sub>3</sub> cluster, vary
with growth conditions in N-rich and Al-rich environments. Using the
calculation results as bases, we develop a three-step metalorganic
vapor-phase epitaxy, which involves the periodic growth sequence of
(i) trimethylaluminum (TMAl), (ii) ammonia (NH<sub>3</sub>), and (iii)
TMAl+NH<sub>3</sub> supply, bringing in hierarchical growth units
to improve AlN layer compactness. A series of AlN samples were grown,
and their morphological and luminescent evolutions were evaluated
by atomic force microscopy and cathodoluminescence, respectively.
The proposed technique is advantageous because the boundaries and
defect-related luminescence derived are highly depressed, serving
as a productive platform from which to further optimize the properties
of AlGaN semiconductors
The Effects of Different CoreāShell Structures on the Electrochemical Performances of SiāGe Nanorod Arrays as Anodes for Micro-Lithium Ion Batteries
Connected
and airbag isolated SiāGe nanorod (NR) arrays
in different configurations have been fabricated on wafer scale Si
substrates as anodes in micro-lithium ion batteries (LIBs), and the
impacts of configurations on electrochemical properties of the electrodes
were investigated experimentally and theoretically. It is demonstrated
that the Si inner cores can be effectively protected by the connected
Ge shells and contribute to the enhanced capacity by ā¼68%,
derived from an activation process along with the amorphization of
the crystalline lattice. The first-principles calculations further
verify the smaller forces on the Si layers at the atomic level during
the restricted volume expansion with the covering of Ge layers. This
work provides general guidelines for designing other composites and
coreāshell configurations in electrodes of micro-LIBs to accomplish
higher capacities and longer cycle lives
Additional file 1: of Tuning the Surface Morphologies and Properties of ZnO Films by the Design of Interfacial Layer
Supplementary experimental data for ZnO films grown on MgO (111). Table S1. Detailed growth conditions for ZnO film samples. Figure S1. AFM results. (a)-(e) AFM images of the ZnO film surface morphologies in 5ĆÅŗm; (f)-(j) magnified images of the square areas (marked by dashed black lines) in (a)-(e). Figure S2. SEM results. SEM images for ZnO films with typical particle and ridge surface morphologies. Figure S3. XRD results. XRD plots for MgO (111) substrate and films. Figure S4. PL results. Room temperature PL spectra of ZnO films. (PDF 88ĆĀ kb
Synergetic SERS Enhancement in a Metal-Like/Metal Double-Shell Structure for Sensitive and Stable Application
Because
of either thermal/chemical instability or high optical loss in noble
metal nanostructures, searching for alternative plasmonic materials
is becoming more and more urgent, considering the practical biosensing
applications under various extreme conditions. In this work, titanium
nitride (TiN), a low-loss metal-like material with both excellent
thermal and excellent chemical stabilities, was proposed to composite
with Ag hollow nanosphere (HNS) nanostructures as an effective surface-enhanced
Raman scattering (SERS) substrate to realize both highly sensitive
and highly stable molecular detection. Because of the multiple-mode
local surface plasmon resonance around the spherical composite nanospheres
and the āgap effectā derived from the ultrasmall nanogaps
within the precisely controlled plasmonic arrays, an intensively enhanced
local field was successfully induced on this SERS substrate. Combined
with the unique charge transferring process between Ag and TiN, a
synergistically enhanced SERS sensitivity involving both physical
and chemical mechanisms was achieved. Especially, with the isolation
of TiN, a time-durable Raman detection on these TiNāAg HNS
arrays was accomplished, showing great potential for practical applications
High Stability Induced by the TiN/Ti Interlayer in Three-Dimensional Si/Ge Nanorod Arrays as Anode in Micro Lithium Ion Battery
Three-dimensional (3D) Si/Ge-based
micro/nano batteries are promising
lab-on-chip power supply sources because of the good process compatibility
with integrated circuits and Micro/Nano-Electro-Mechanical System
technologies. In this work, the effective interlayer of TiN/Ti thin
films were introduced to coat around the 3D Si nanorod (NR) arrays
before the amorphous Ge layer deposition as anode in micro/nano lithium
ion batteries, thus the superior cycling stability was realized by
reason for the restriction of Si activation in this unique 3D matchlike
Si/TiN/Ti/Ge NR array electrode. Moreover, the volume expansion properties
after the repeated lithium-ion insertion/extraction were experimentally
investigated to evidence the superior stability of this unique multilayered
Si composite electrode. The demonstration of this wafer-scale, cost-effective,
and Si-compatible fabrication for anodes in Li-ion micro/nano batteries
provides new routes to configurate more efficient 3D energy storage
systems for micro/nano smart semiconductor devices
One-Pot Synthesis of Superfine CoreāShell Cu@metal Nanowires for Highly Tenacious Transparent LED Dimmer
We demonstrate a
one-pot, low-cost, and scalable method for fast synthesis of superfine
and uniform coreāshell Cu nanowires (NWs) coated with optional
metals and/or alloy. Cu NWs in high aspect ratio (>3000) were synthesized
through an oleylamine-mediated solution method, and tunable shell
coating was performed by injecting metal-organic precursors at the
last stage of reaction. Superfine Cu@metal NWs (Ti, Zn, V, Ni, Ag,
NiZn, etc) were achieved in diameter of ā¼30 nm and length of
ā¼50 Ī¼m. Transparent conductive films were obtained by
imprinting method, showing high optoelectronic performance (51 Ī©/sq
at 93% transmittance), high mechanical tenacity over bending, twisting,
stretching, and compressing, and robust antioxidant ability (high
temperature and high humidity). A transparent film dimmer for light-emitting
diode (LED) lighting was fabricated with the stretchable Cu@Ti NWs
network. The LED luminance could be accurately tuned by the deformation
strain of Cu@Ti NWs film
One-Pot Synthesis of Superfine CoreāShell Cu@metal Nanowires for Highly Tenacious Transparent LED Dimmer
We demonstrate a
one-pot, low-cost, and scalable method for fast synthesis of superfine
and uniform coreāshell Cu nanowires (NWs) coated with optional
metals and/or alloy. Cu NWs in high aspect ratio (>3000) were synthesized
through an oleylamine-mediated solution method, and tunable shell
coating was performed by injecting metal-organic precursors at the
last stage of reaction. Superfine Cu@metal NWs (Ti, Zn, V, Ni, Ag,
NiZn, etc) were achieved in diameter of ā¼30 nm and length of
ā¼50 Ī¼m. Transparent conductive films were obtained by
imprinting method, showing high optoelectronic performance (51 Ī©/sq
at 93% transmittance), high mechanical tenacity over bending, twisting,
stretching, and compressing, and robust antioxidant ability (high
temperature and high humidity). A transparent film dimmer for light-emitting
diode (LED) lighting was fabricated with the stretchable Cu@Ti NWs
network. The LED luminance could be accurately tuned by the deformation
strain of Cu@Ti NWs film
Growth Mechanism and Controlled Synthesis of AB-Stacked Bilayer Graphene on CuāNi Alloy Foils
Strongly coupled bilayer graphene (<i>i.e.</i>, AB stacked) grows particularly well on commercial ā90ā10ā CuāNi alloy foil. However, the mechanism of growth of bilayer graphene on CuāNi alloy foils had not been discovered. Carbon isotope labeling (sequential dosing of <sup>12</sup>CH<sub>4</sub> and <sup>13</sup>CH<sub>4</sub>) and Raman spectroscopic mapping were used to study the growth process. It was learned that the mechanism of graphene growth on CuāNi alloy is by precipitation at the surface from carbon dissolved in the bulk of the alloy foil that diffuses to the surface. The growth parameters were varied to investigate their effect on graphene coverage and isotopic composition. It was found that higher temperature, longer exposure time, higher rate of bulk diffusion for <sup>12</sup>C <i>vs</i> <sup>13</sup>C, and slower cooling rate all produced higher graphene coverage on this type of CuāNi alloy foil. The isotopic composition of the graphene layer(s) could also be modified by adjusting the cooling rate. In addition, large-area, AB-stacked bilayer graphene transferrable onto Si/SiO<sub>2</sub> substrates was controllably synthesized
Additional file 1: Figure S1. of Synthesis of ZnO/Si Hierarchical Nanowire Arrays for Photocatalyst Application
High resolution XPS spectra of ZnO/Si nanowire arrays before and after photocatalysis. (a1āa3) Deconvolution of C (1s), O (1s), and Zn (2p) core levels in sample ALD before photocatalysis. (b1āb3) Deconvolution of C (1s), O (1s), and Zn (2p) core levels in sample ALD after photocatalysis. (c1āc3) Deconvolution of C (1s), O (1s), and Zn (2p) core levels in sample MS before photocatalysis. (d1ād3) Deconvolution of C (1s), O (1s), and Zn (2p) core levels in sample MS after photocatalysis. Figure S2. Spectral intensity of different bonds after photocatalysis (I) in contrast to that of before photocatalysis (I0) for sample ALD and sample MS as calculated from the deconvoluted spectra in Figure S1. (i) C-C bond, (ii) C-O-Zn bond, (iii) O-Zn bond, (iv) O-H bond or oxygen vacancies, (v) Zn 2p3/2, and (vi) Zn 2p1/2. (DOC 307Ā kb