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 “stadiums” 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, Al–N molecule, and Al–N₃ 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 (NH₃), and (iii) TMAl+NH₃ 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 Core–Shell Structures on the Electrochemical Performances of Si–Ge Nanorod Arrays as Anodes for Micro-Lithium Ion Batteries

Connected and airbag isolated Si–Ge 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 ∼68%, 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 core–shell 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 5Οm; (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 88 kb

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

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 “gap effect” 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 TiN–Ag HNS arrays was accomplished, showing great potential for practical applications

One-Pot Synthesis of Superfine Core–Shell 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 core–shell 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 ∼30 nm and length of ∼50 μm. Transparent conductive films were obtained by imprinting method, showing high optoelectronic performance (51 Ω/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 Core–Shell 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 core–shell 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 ∼30 nm and length of ∼50 μm. Transparent conductive films were obtained by imprinting method, showing high optoelectronic performance (51 Ω/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 Cu–Ni Alloy Foils

Strongly coupled bilayer graphene (<i>i.e.</i>, AB stacked) grows particularly well on commercial “90–10” Cu–Ni alloy foil. However, the mechanism of growth of bilayer graphene on Cu–Ni alloy foils had not been discovered. Carbon isotope labeling (sequential dosing of ¹²CH₄ and ¹³CH₄) and Raman spectroscopic mapping were used to study the growth process. It was learned that the mechanism of graphene growth on Cu–Ni 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 ¹²C <i>vs</i> ¹³C, and slower cooling rate all produced higher graphene coverage on this type of Cu–Ni 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/SiO₂ 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. (a1–a3) Deconvolution of C (1s), O (1s), and Zn (2p) core levels in sample ALD before photocatalysis. (b1–b3) Deconvolution of C (1s), O (1s), and Zn (2p) core levels in sample ALD after photocatalysis. (c1–c3) Deconvolution of C (1s), O (1s), and Zn (2p) core levels in sample MS before photocatalysis. (d1–d3) 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 307 kb