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Multifunctional and smart solar-blind photodetectors are of great significance for many applications, particularly for communications, optoelectronic circuits, and environmental risk monitoring. In this study, a wire-shaped photoanode of the solar-blind photoelectrochemical (PEC)-type photodetector based on an α-Ga2O3 nanorods/electrolyte solid/liquid heterojunction is realized. In photovoltaic devices, a junction generally comprises two different solid materials to facilitate the separation of photogenerated electron–hole pairs. Similarly, a solid/liquid junction is formed between the semiconductor and the electrolyte in a PEC photodetector. The apparent rectification characteristics of the dark current indicate that the energy bands bend at the α-Ga2O3 nanorods/electrolyte interface. The local electric field in the semiconductor effectively promotes the separation of carriers. The photodetectors exhibit a high light/dark current ratio ( Ilight/ Idark) of 68.7; fast rise and decay response times of 0.1 and 0.06 s, respectively; and a high responsivity of 11.2 mA/W (@230 nm) at zero bias. The wire-shaped photoanode is beneficial for realizing potential omnidirectional solar-blind detection.

In this Letter, we present the experimental observation of trilayer exciton emission in the WSe2/WS2/MoS2 heterostructures by photoluminescence spectroscopy at a low temperature of ∼10 K. It is found that the trilayer exciton has a lower exciton binding energy than that in the WSe2/MoS2 heterobilayer due to the insertion of monolayer WS2, which is manifested by the blueshift of this trilayer exciton peak relative to the bilayer exciton. Through the measurements of the exciton peak position as a function of excitation power, the trilayer excitons exhibited the density-dependent repulsive interaction among them, and the reduction of binding energy ∼8 meV is deduced. Moreover, the trilayer exciton has a longer lifetime than the bilayer exciton, resulting from the reduction of electron–hole wavefunction overlap.

The multifunctional and smart ultraviolet photodetectors are of great significance and necessity for applications in many fields, especially in health and environmental risk monitoring. Hence, a wire-shaped photoelectrochemical type ultraviolet photodetector based on photoanode of TiO2 nanotube arrays (TNAs) fabricated by electrochemical anodization is demonstrated in this work. The TNAs can provide direct pathways for carriers and large internal surface area. The assembled UV detector presented a high photocurrent density of 110 μA cm−2, a high ON/OFF ratio of 467, and a fast rise and decay response time of 13 and 19 ms for the optimal thickness of the photoanode of TNAs. Moreover, the detectors also exhibited visible-blind characteristics and an excellent linear response even under weak irradiation (20–100 μW cm−2). The results are beneficial to realizing omnidirectional and wearable optoelectronic devices.

Realizing a balance between water supply and the evaporation of photothermal evaporators is a valuable means to enhance the solar–thermal evaporation rate, but practical obstacles remain. The interfacial mechanics of a Janus evaporator with an interpenetrating structure are proposed to achieve a dramatic improvement in the solar–thermal evaporation rate. The Janus evaporator is composed of a membrane material of Cu1.96S grown in situ on a foamed copper skeleton (CF@Cu1.96S) and a graphene oxide/sodium alginate aerogel (GA), through an interfacial freeze-drying shape technology. In this unique architecture, the superhydrophilic GA can be stretched into the hydrophobic CF@Cu1.96S interior to build an interpenetrating network architecture (CF@Cu1.96S/GA), thereby adjusting the Laplace pressure and constraining capillarity. Due to the optimized water supply of interfacial mechanics, the CF@Cu1.96S/GA evaporator achieves an evaporation rate of 1.79 kg m−2 h−1 under 1 sun irradiation and exhibits superior salt resistance. This provides a rationale for the reasonable design of the structure of the solar–thermal evaporators.

In-plane propagation of excited light in layered materials boosts the observation of novel phenomena, which differ from out-of-plane propagation. In this work, we perform the Raman study with light propagation parallel to the plane of layered MoS2. The Raman signal is unveiled at least an order of magnitude larger than that perpendicular to the plane when the excitation photon energy at ∼2.81 eV. We attribute this high-yield Raman spectra to the stronger photon–exciton coupling with in-plane propagation of light. Furthermore, we show that the exciton-mediated phonon excitation in the first-order Raman process is dominant with consideration of angular momentum transfer between phonons and photons through the measurements of the circularly polarized Raman spectra. This experimental setup configuration paves a way with high efficiency to investigate the phonon information in layered materials.

Accurate and rapid prediction of dielectric constant (e) for polymer-based dielectrics at various frequencies remains challenging. We construct a dataset of dielectrics with an easily attainable numerical representation scheme. We propose an interval support vector regression with a particle swarm optimization to accelerate the e prediction, discovery, and design of polymer dielectrics at various frequencies (spanning from 100 Hz to 1015 Hz). The key features affecting dielectric constant could be identified, and this is highly valuable to target the discovering of polymer dielectrics as high-throughput screening and tailor the desirable property.

Three-dimensional tubular origami, fabricated by the self-rolling of functional nanomembranes, is of great interest due to its numerous opportunities for applications in photochemical sensing, intelligent actuators, microrobots, electronics, and many others. A continuing opportunity of this area is in the development of strategies for fabricating tubular origami, in solvent-free and low-cost conditions. This paper proposed a semidry release approach, allowing for the sacrificial layer-free, vapor-assisted self-rolling, and recyclable use of substrates, to create microscale tubular origami. Interface engineering designs that involve hydrophilic and hydrophobic material stacks are introduced to realize the semidry release of nanomembranes, which finally self-roll into multifunctional tubular structures. Systematic experimental and theoretical studies demonstrate the controllability of their dimensions. Finally, a bioresorbable microtube with potential for transient implantable devices is demonstrated. Our present work adds to the portfolio of routes for the construction of tubular origami, which can be utilized as functional platforms for fundamental studies and practical applications.

Subnanosecond switching speed from an amorphous state with stable crystal precursors to the crystalline state was recently achieved in amorphous Sc-doped Sb2Te3 (a-SST) phase change materials (PCMs), which is about two orders of magnitude faster than that in the well-studied Ge2Sb2Te5 and Ge1Sb2Te4 PCMs. However, the phase change mechanism and phase stability of a-SST remain unknown. Here, we prepared amorphous Sc0.3Sb2Te3 nanocomposites within a minute amount of face-centered-cubic (FCC) type nanograins embedded in the amorphous matrix. Using in situ high-pressure synchrotron X-ray diffraction, we found that nanograins were frustrated under high pressure and gradually dissolved into the matrix around 11.0 GPa. Beyond 11.0 GPa, the a-SST matrix transformed into a uniform high density metallic like amorphous state with a five orders of magnitude drop in electric resistivity compared to the pristine materials. When further compressed to 23.97 GPa, the high density amorphous (HDA) phase switched into a body-centered-cubic (BCC) high-pressure structure, a different phase from the ambient pressure crystalline structure. Upon decompression back to ambient pressure, a pure amorphous phase was sustained. The present study provides additional insight into the phase change mechanism of amorphous nanocomposites.

In distinction to the generally utilized chemical vapor deposition (CVD) synthesis that leads to multilayer graphene growth by carbon (C) synthesis from nickel (Ni), we proposed a controllable strategy to synthesize graphene on an arbitrary substrate through ion implantation technology, where the layer number of the obtained graphene film is accurately controlled by the corresponding dose of implanted C ions. To be specific, an oxide layer (NiO) was introduced as the barrier to prevent implanted C atom precipitation at the surface but at the interface. Various unusual substrates (such as sapphire, glass, SiO2, and Si), in terms of traditional CVD, have been utilized for growing high-quality graphene. Employing the as-grown graphene/Si, Schottky junction-based photodetectors with high responsivity (63 mA W−1) and high detectivity (∼1.4 × 1010 cm Hz1/2 W−1) at 1550 nm are demonstrated without requiring any post-transfer process, thus avoiding additional contaminations, complexities, and costs during device fabrications. Our works afford a versatile technique for growing graphene on arbitrary substrates, with controllable layer numbers and transfer-free optoelectronic device fabrications, thus accelerating their further practical applications in electro-optical devices.

This paper describes a simple and convenient approach to synthesize large amounts of ZnO nanosheets, which are suitable for producing a key component, i.e., colloidal nanoink, of printed ultraviolet photodetectors. ZnO nanosheets are produced by atomic layer deposition, where a three-dimensional polymer sponge with a large specific surface area is used as the template. Systematic studies including scanning electron microscopy, X-ray diffraction, and transmission electron microscopy reveal that the synthesized ZnO nanosheets have a good crystalline quality and mechanical flexibility. After dispersing ZnO nanosheets in a solvent to form a stable and colloidal nanoink, an ultraviolet photodetector is demonstrated through the printing method. Such a printed ultraviolet photodetector that utilizes ZnO nanosheets as the functional materials exhibits a high responsivity of ∼148 A/W and a response time of 19 s. Our present study may provide a practical method to produce large amounts of functional nanosheets for printing electronics, which paves the way for developing high-performance, low-cost, large-area printed, and flexible electronics.

Topological Hall effect (THE) as one of spin-related effects originates from scalar spin chirality formed by non-coplanar spin structures, being a promising tool for probing the change of electron spin. Single-phase (022) Mn4N films with coplanar spin structures were prepared on unpoled ferroelectric [Pb(Mg1/3Nb2/3)O3]0.67-[PbTiO3]0.33 (PMN-PT) substrates. The transport properties of Mn4N/PMN-PT have been investigated. The decreased magnetization and anomalous resistivity imply that the spin states of Mn4N are influenced by ferroelectric polarization of the substrate. The observation of THE in the Mn4N/PMN-PT heterostructure strongly supports that the spin states of Mn4N are modified. After poling PMN-PT, the enhanced THE peak magnitude verifies that the spin states of Mn4N are tuned by ferroelectric polarization. This study provides a non-magnetic method for manipulation of spin states, which could avoid the external magnetic field perturbations.

A method for preparing a quantum dot (QD)-white light-emitting diode (WLED) is reported. Holes were etched in the SiO2 layer deposited on the sapphire substrate of the flip-chip LED by inductively coupled plasma, and these holes were then filled with QDs. An ultraviolet-curable resin was then spin-coated on top of the QD-containing SiO2 layer, and the resin was cured to act as a protecting layer. The reflective sidewall structure minimized sidelight leakage. The fabrication of the QD-WLED is simple in preparation and compatible with traditional LED processes, which was the minimum size of the WLED chip-scale integrated package. InP/ZnS core-shell QDs were used as the converter in the WLED. A blue light-emitting diode with a flip-chip structure was used as the excitation source. The QD-WLED exhibited color temperatures from 5900 to 6400 K and Commission Internationale De L'Elcairage color coordinates from (0.315, 0.325) to (0.325, 0.317), under drive currents from 100 to 400 mA. The QD-WLED exhibited stabl...

Controllable cracking behaviors are realized in Si with a buried B doped Si0.70Ge0.30 interlayer by tuning the H+ projected ranges using the traditional H implantation technique. When the projected range is shallower (deeper) than the depth of the buried Si0.70Ge0.30 layer, cracking occurs at the interface between the top Si layer (bottom handle Si wafer) and the Si0.70Ge0.30 interlayer, thus resulting in the formation of continuous sharp crack confined at the Si0.70Ge0.30/Si interfaces. For the case that the H-ion projected range is located at the B-doped Si0.70Ge0.30 buried interlayer, continuous cracking is observed along the interlayer, which is similar to the conventional ion-cut method. We attribute these controlled cracking behaviors to the B doped Si0.70Ge0.30 interlayer, which holds a large amount of B impurities and compressive strain, and H ions can be trapped and confined at the interfaces or within the interlayer (depended on projected ranges) to facilitate the formation of cracks.

Various kinds of materials have been developed as transparent conductors for applications in semiconductor optoelectronic devices. However, there is a bottleneck that transparent conductive materials lose their transparency at ultraviolet (UV) wavelengths and could not meet the demands for commercial UV device applications. In this work, textured indium tin oxide (ITO) is grown and its potential to be used at UV wavelengths is explored. It is observed that the pronounced Burstein-Moss effect could widen the optical bandgap of the textured ITO to 4.7 eV. The average transmittance in UVA (315 nm–400 nm) and UVB (280 nm–315 nm) ranges is as high as 94% and 74%, respectively. The excellent optical property of textured ITO is attributed to its unique structural property. The compatibility of textured ITO thin films to the device fabrication is demonstrated on 368-nm nitride-based light emitting diodes, and the enhancement of light output power by 14.8% is observed compared to sputtered ITO.

Tubular germanium (Ge) resistors are demonstrated by rolling-up thin Ge nanomembranes (NMs, 50 nm in thickness) with electrical contacts. The strain distribution of rolled-up Ge microtubes along the radial direction is investigated and predicted by utilizing micro-Raman scattering spectroscopy with two different excitation lasers. Electrical properties are characterized for both unreleased GeNMs and released/rolled-up Ge microtubes. The conductivities of GeNMs significantly decrease after rolling-up into tubular structures, which can be attributed to surface charging states on the conductance, band bending, and piezo-resistance effect. When illuminated with a light source, facilitated by the suppressed dark current of rolled-up Ge tubes, the corresponding signal-to-noise ratio can be dramatically enhanced compared with that of planar GeNMs.

The application of epitaxial yttrium iron garnet (YIG) thin film on high frequency on-chip spiral inductors is investigated. The YIG thin film with the thickness of 3.6 μm was grown on GGG(111) substrate using the liquid phase method, which exhibits relatively high saturation magnetization 4πMs of 1615 Oe close to the bulk value of 1750 Oe and low initial coercivity Hc of 0.5 Oe that minimizes the hysteretic losses. Subsequently, the spiral inductors were directly fabricated on the YIG/GGG(111) substrate. The results show substantial improvement in the optimum operating frequency and self-resonance frequency of the on-chip spiral inductor with the YIG thin film with an increase of 50% up to ∼7.5 GHz and 14.2 GHz, respectively, implying that on-chip spiral inductors with the YIG thin film can be applied to much higher frequency RF circuits.

Epitaxial Ba1−xSrxTiO3 (BST) thin films with different Ba∕Sr ratio (x=0.1–0.9 with an interval of 0.1) have been grown on (001) LaAlO3 substrates using polymer-assisted deposition. Dielectric measurements show that the films have dielectric properties comparable to the BST films grown by the pulsed laser deposition. Systematic changes in the lattice parameters and dielectric behavior with x values have been measured. The highest dielectric constant (∼1010) and tunability (∼69%) at 1MHz and room temperature have been obtained at x=0.3, which is at the phase boundary of tetragonal and cubic structures.

Developments in optoelectronics and spin-optronics based on transition metal dichalcogenide monolayers (MLs) need materials with efficient optical emission and well-defined transition energies. In as-exfoliated MoS2 MLs the photoluminescence (PL) spectra even at low temperature consists typically of broad, overlapping contributions from neutral, charged excitons (trions) and localized states. Here we show that in superacid treated MoS2 MLs the PL intensity increases by up to 60 times at room temperature. The neutral and charged exciton transitions are spectrally well separated in PL and reflectivity at T=4 K, with linewidth for the neutral exciton of 15 meV, but with similar intensities compared to the ones in as-exfoliated MLs at the same temperature. Time resolved experiments uncover picoseconds recombination dynamics analyzed separately for charged and neutral exciton emission. Using the chiral interband selection rules, we demonstrate optically induced valley polarization for both complexes and valley coherence for only the neutral exciton.

We report a technique for epitaxial thin-film growth by combination of selective heteroepitaxial and lateral homoepitaxial growth. (Ba,Sr)TiO3 (BST) thin films were deposited on LaAlO3 having amorphous SiOx masking layers with stripe patterns at 450 °C by pulsed-laser deposition. Postannealing was carried out thereafter for lateral epitaxial growth. The difference in BST nucleation temperatures from the amorphous masking regions and lattice-matched single-crystalline substrates enables selective nucleation. Heteroepitaxial growth takes place in the regions of single-crystalline substrates, whereas lateral homoepitaxial growth evolves from the crystallized BST towards the SiOx masked region during postannealing process.

The temperature-dependent frequency shift of resonant Raman spectra of double-wall carbon nanotubes is investigated in the range of 78–650 K. We show here that different radial breathing mode (RBM) peaks, which are relative to different tube diameters, have a different temperature coefficient of frequency shift, and the larger diameter carbon nanotubes have more RBM frequency downshift with increasing temperature. We attribute the RBM frequency variation to the temperature dependence of the stretching force constant of C–C bond.

Thin films consisting of self-assembled chromophoric superlattices exhibit very large second-order nonlinear responses [χ(2)]. Using such films, a “static” diffraction grating is created by the interference of two coherent infrared beams from a pulsed yttritium–aluminum–garnet laser. This grating is used to switch the second-harmonic and third-harmonic “signal” beams (generated from the fundamental “pump” beam or mixed within the chromophoric superlattice) into different channels (directions). Ultrafast switching response as a function of the time overlap of the pumping beams is demonstrated. It is suggested that such devices can be used to spatially and temporally separate signal trains consisting of pulses having different frequencies and arrival times.

Iodine-doped multiwall carbon nanotubes ~I-MWNTs! were characterized by means of Raman scattering and thermogravimetric analysis. The results show that multiwall carbon nanotubes ~MWNTs! can be effectively doped by iodine and exchange electrons with iodine. Iodine atoms form charged polyiodide chains inside tubes of different inner diameter, which is similar to the iodine-doped single-wall carbon nanotubes ~I-SWNTs!, but can not intercalate into the graphene walls of MWNTs. The Raman scattering behavior of I-MWNTs exhibits some differences from that of I-SWNTs and the low-dimensional conductive hydrocarbon-iodine complex ‘‘peryleneiI 2.92 .’’ © 2002 American Institute of Physics. @DOI: 10.1063/1.1468269#

The second-order susceptibilities in the ZnO films have been studied systemically. In very thin films, we observe an enhancement of second-order susceptibilities, which is larger than that of single-crystal ZnO. It was also observed that the second-order susceptibilities for ZnO films depend on the thickness but not on the film growth technique used (reactive sputtering or plasma-enhanced chemical vapor deposition). We suggest a mechanism to explain the reduction in the second-order susceptibilities of the thicker films.

In this letter, we report the catalytic synthesis of a large amount of straight carbon nanotubes using a transition-metal cobalt–nickel/zeolite catalyst. High-resolution transmission electron microscopy images show that they are well graphitized. Raman spectrum shows its peak at 1349 cm−1 (D band) is much weaker than that at 1582 cm−1 (G band). We believe that straight carbon nanotubes contain much less defects than curved nanotubes and might have potential applications in the future.

High hole concentration was achieved in Mg-doped AlxGa1−xN (x ∼ 0.4) by using indium-surfactant-assisted delta doping method. A maximum carrier concentration of 4.75 × 1018 cm−3 was obtained, which is three times higher than that of the conventionally delta-doped sample. Sheet resistivity as low as 2.46 × 104 Ω/sq was realized, benefiting from the high hole concentration (p). Analysis results show that the Mg incorporation is effectively enhanced, while the compensation ratio and acceptor activation energy (EA) are significantly reduced by using In surfactant. It was also found that the In surfactant may induce stronger valence-band modulation, contributing to the decrease of EA and the increase of p.

Anomalous Hall effect (AHE) in ferrimagnetic Mn4N epitaxial films grown by molecular-beam epitaxy is investigated. The longitudinal conductivity σxx is within the superclean regime, indicating Mn4N is a highly conducting material. We further demonstrate that the AHE signal in 40-nm-thick films is mainly due to the extrinsic contributions based on the analysis fitted by ρAH=a′ρxx0+bρxx2 and σAH∝σxx. Our study not only provide a strategy for further theoretical work on antiperovskite manganese nitrides but also shed promising light on utilizing their extrinsic AHE to fabricate spintronic devices.

We have successfully grown carbon nanotubes on cobalt-implanted silicon with various doses. The morphology of such tubes has been examined by scanning electron microscopy, transmission electron microscopy, and Raman scattering. On contrary to the commonly used transition-metal nanoparticle catalysts, nanometer-sized CoSi2 precipitates produced in the as-implanted substrates are believed to act as nucleation centers for the formation of carbon nanotubes.

We demonstrate charge tuning in strain free GaAs/AlGaAs quantum dots (QDs) grown by droplet epitaxy on a GaAs(111)A substrate. Application of a bias voltage allows the controlled charging of the QDs from $-3|e|$ to $+2|e|$. The resulting changes in QD emission energy and exciton fine-structure are recorded in micro-photoluminescence experiments at T=4K. We uncover the existence of excited valence and conduction states, in addition to the s-shell-like ground state. We record a second series of emission lines about 25meV above the charged exciton emission coming from excited charged excitons. For these excited interband transitions a negative diamagnetic shift of large amplitude is uncovered in longitudinal magnetic fields., Comment: 5 pages, 3 figures

Pure Ni film is the first metal catalyst that can generate graphene with small domains and variable thickness across the film. The lack of control over layer number is attributed to the high carbon solubility of Ni. We designed a combinatorial Ni/Si system, which enables the direct growth of monolayer graphene via chemical vapor deposition method. In this system, Si was introduced as the carbon diffusion barriers to prevent carbon diffusing into Ni film. The designed system fully overcomes the fundamental limitations of Ni and provides a facile and effective strategy to yield homogenous monolayer graphene over large area. The field effect transistors were fabricated and characterized to determine the electrical properties of the synthesized graphene film. Furthermore, this technique can utilize standard equipments available in semiconductor technology.

Wetting transitions were studied with vertically vibrated droplet on various polydimethylsiloxane surfaces with square array of pillars. Our experiments show that the increase of the pillar spacing, at each given frequency, leads to a decrease of the critical amplitude (which is required to achieve a Wenzel to Cassie transition). The physical mechanism of Wenzel-Cassie transition by vibration is presented. Compared with other studies of wetting transition by vibration, we demonstrate that Wenzel-Cassie transition comes up when R(θ)fn2Acr2≈const (where fn is the resonance frequency, Acr is the threshold amplitude, and R(θ) is the initial radius of the droplet).

In contrast to the commonly used chemical vapor deposition growth that leads to multilayer graphene formation by carbon segregation from the Ni bulk, we designed a Ni-Ge binary system to directly grow graphene film on Ni-Ge binary substrate, via chemical vapor deposition with methane and hydrogen gas as precursors. Our system fully overcomes the fundamental limitations of Ni and yields homogenous single layer graphene over large areas. The chemical vapor deposition growth of graphene on Ni-Ge binary substrate shows that self limiting monolayer graphene growth can be obtained on these substrate.

We demonstrate a simple low-cost approach as an alternative to conventional O2 plasma treatment to modify the surface of indium tin oxide (ITO) anodes for use in organic light-emitting diodes. ITO is functionalized with F− ions by electrochemical treatment in dilute hydrofluoric acid. An electrode with a work function of 5.2 eV is achieved following fluorination. Using this electrode, a maximum external quantum efficiency of 26.0% (91 cd/A, 102 lm/W) is obtained, which is 12% higher than that of a device using the O2 plasma-treated ITO. Fluorination also increases the transparency in the near-infrared region.

This paper introduces a simple transfer technique named as rolling-transfer technology to transfer Si nanomembranes to pre-stressed elastomers with nearly 100% transfer efficiency. When transferred onto the elastomeric substrate, wave-like wrinkled Si nanomembranes with uniform periodicity and amplitude are formed. The three dimensional (3-D) strain distribution of the wrinkled Si nanomembranes has been investigated in detail through the micro-Raman mapping using two excited laser wavelengths. The sinusoidal bulking geometry of Si nanomembrane results in a periodical strain alternation along x direction, while a homogenous strain distribution in y direction. The inhomogeneous strain distribution along z direction can be interpreted with the physical model considering the shift of the neutral mechanical plane, which is qualitatively determined by the Von Karman elastic nonlinear plate theory, including the bending effect and the shear forces existing at the Si nanomembrane/elastomeric substrate interface.

Hole transport control and carrier injection improvement have been demonstrated in the InGaN/GaN light-emitting diodes (LEDs) with step-stage multiple-quantum-well (MQW) structure and Si-doped hole-blocking barriers. Single-wavelength emission was obtained under electrical pumping in these LEDs by utilizing hole-blocking effect. The light emission around 450 nm showed a substantial increase compared with the reference sample with single or step-stage indium-content MQWs. The droop behavior and wavelength stability were also improved significantly. These improvements were attributed to the enhanced carrier injection to the active region due to the alleviation of the quantum-confined Stark effect and the effective hole-blocking effect of the Si-doped barriers.

The efficiency of Microcystis aeruginosa plasma inactivation was investigated using dielectric barrier discharge low-temperature plasma. The inactivation efficiency was characterized in terms of optical density. The influence of electrical and physicochemical parameters on M. aeruginosa inactivation was studied to determine the optimal experimental conditions. The influence of active species was studied. The proliferation of the M. aeruginosa cells was significantly decreased under plasma exposure. The morphologic changes in M. aeruginosa were characterized under scanning electron microscopy. These results suggest that the low-temperature plasma technology is a promising method for water pollution control.

The source responsible for V2 (1.398 eV) luminescence in 6H-SiC is recognized as a favorable defect for quantum information processing. However, the origin of V2 luminescence is still controversial. With careful photoluminescence measurements, it is found that V2 line shows clear bound exciton luminescence features. Furthermore, a mechanism based on neutral vanadium donor bound exciton is put forward to explain the origin of V2 luminescence. The results may provide some insights to understanding the nature of the promising qubit candidates in SiC.

GaN-based light emitting diodes (LEDs) with shallow triangular quantum wells (TQW) structure were proposed and investigated. LEDs with shallow TQW demonstrated a lower turn-on voltage and 80% higher lighting efficiency at 20 mA than devices without the shallow QW structure. A more stable emission wavelength and a lower ideality factor were achieved with the proposed structure. X-ray reciprocal space mapping revealed a partial strain relaxation in active region due to the insertion of the TQW structure. The improved performance is ascribed to the weakening of the polarization field in the MQW active region induced by the TQW structure.

We report the anomalous mobility properties of Si-delta-doped GaN with periodically doping profile. Samples with different delta-doping periods or with varied Si source flow were investigated. It is found that for the short delta-doping-period (

Nitrogen-vacancy-induced magnetism in AlN is investigated both theoretically and experimentally. First-principles calculations reveal that magnetic coupling between the vacancy-induced moments varies with the vacancy concentration. A sizable ferromagnetic coupling for nitrogen vacancies is found. Experimentally, the magnetism manipulation is realized accordingly by introducing vacancies through varying the nitrogen atmosphere in AlN whiskers. The vacancy control may be applicable to other III-V nitride semiconductors in tuning their magnetism.

We report that single-walled carbon nanotubes (SWNTs) can be etched into graphene nanoribbons (GNRs) by iron etching, which is confirmed by Raman spectroscopy and transmission electron microscopy. Compared with SWNTs, there are some unique features in Raman spectra of GNRs: symmetric G peak with no splitting, larger Raman intensity of 2D peak than G peak, and lower frequency and narrower full width at half maximum for 2D peak. Similar to radial breathing modes in SWNTs, theoretically predicted radial breathing-like mode of GNRs is also observed: a clear and prominent peak around 223 cm−1 in the low frequency regions. This work paves the way for future studies of nanodevices based on SWNT-GNR heterojunction.

We demonstrated flexible, ultrathin, and transparent sound-emitting devices (SEDs) using silver nanowires (AgNWs). Large area of AgNWs film on substrate was made by dry transfer technique. The sound emission from the AgNWs was measured as a function of power, distance, and frequency. Significant flat and wide frequency responses occurred between 15 and 45 kHz. The sound pressure was in good agreement with theoretical results. This indicates that a thermoacoustic effect exists in AgNWs. The AgNWs-SEDs can be integrated with the liquid crystal display, which shows the potential to be an important component in flexible electronic systems.