Polarization-sensitive photodetectors based on two-dimensional (2D) materials have shown more attractive application prospects compared to traditional thin-film photodetectors due to their atomic thickness, tunable bandgap, high mobility and strong light–matter interactions. Among them, 2D molybdenum disulfide (MoS2) has drawn numerous attentions in photodetection due to its wide spectral range, remarkable photoresponsivity and fast photo-switching rate. However, the isotropic crystal structure of MoS2 hampers its application in the polarization-sensitive detection, which is highly desired in military and civilian applications. In this paper, we demonstrated an integration of plasmonic nanocavity with monolayer MoS2 to achieve high photoresponsivity and polarization-sensitive photodetector. With the significant enhancement of electromagnetic field provided by the gap-surface-plasmon (GSP), we achieved a significant photoluminescence (PL) enhancement of 24-fold. Relying on the enhanced light absorption by our plasmonic nanocavity, which generally facilitates photo-generation of electron–hole pairs in MoS2, we achieved a high photoresponsivity of 1.88 A/W and degree of linear polarization (DOLP) of 0.8 at the excitation wavelength of 633 nm. Our work provides a feasible and universal solution to realize polarization-sensitive photodetector of MoS2 for high-performance and polarization-sensitive photodetectors.

Micro/nano origami is a fascinating 3D fabrication technology, showing a strong ability to control structural space degrees of freedom, but which are usually only able to achieve single-direction origami and hence its controlling spatial orientation is still limited to a certain extent. Here, the bidirectional origami induced by focused ion beam irradiation is proposed to break through the freedom of structural space control and realize challenging 3D micro/nanofabrication. It is found that the FIB-induced bidirectional deformation mainly relies on both materials and the ion doses, and the deformation degrees can be tuned by ion irradiated doses, which greatly contributes to construct large numbers of diverse 3D structures. Further, the underlying physics of FIB induced origami are discussed by Monte Carlo simulations along with experiments to reveal that the amounts of atoms sputtering determines the initial direction of deformation. This bidirectional origami exhibits unique capabilities in design and fabrication of versatile 3D metasurface devices. With this strategy, a 3D chiral metasurface composed of an array of bidirectional folded split ring resonators is achieved, showing a giant circular dichorism as high as 0.78/0.85 (Experiment/Simulation) in the mid-infrared region. Such powerful bidirectional origami paves high efficiency approach to broaden 3D micro/nano photonics device.

As an indispensable component of optoelectronic system, an on‐chip light source with well‐defined polarization is desirable in optical communication, signal processing and display applications. The emerging atomically thin transition metal dichalcogenides (TMDCs), due to their high quantum yield and robust valley coherence, provide an unprecedented platform to realize the high‐efficient linearly polarized light emission. Although the valley‐related optical selection rules suggest that valley coherence should be possible, extreme conditions such as cryogenic temperatures are required, which is a long‐term challenge for their practical applications. In this paper, the strongly enhanced linearly polarized emission is realized by integrating WS 2 monolayers with a delicate designed plasmonic nanocavity. It is demonstrated that strong plasmon–exciton coupling gives rise to the plasmon–exciton polariton. The polariton valley coherence results in a linear polarization up to 0.32 at room temperature and contributes to 52% of the total linear polarization. Enhancement of linear polarization through polariton valley coherence can be understood as the consequence of the extra relaxation channel introduced by its plasmonic counterpart. The potential of 2D TMDC‐plasmon hybrid structure appears to be high and of significant technological interest, as well as inspires new perspectives on quantum manipulations in 2D solid‐state systems.

Strain engineering, aiming to tune physical properties of semiconductors, provides a promising paradigm for modern micro/nanoelectronics. Two-dimensional materials (2DMs) are the ideal candidates for the next generation of strain engineered devices because of their intrinsic exceptional mechanical flexibility and strength. However, conventional strain modulation methods in 2DMs cannot satisfy the demand of future device applications, because strained structures by these methods lack consistency, reproducibility, and design flexibility. Here, based on the photoresist degeneration induced by electron irradiation, we present a non-contact approach to accurately and directly write the strains with designed patterns from the nanometer to micrometer scale in 2DMs. Profit from controllable manipulation of the electron beam, the developed strategy offers a capability for constructing tensile, compress, or complex strains in MoSe2 monolayers; hence, unique electronic structures for unique physical properties can be designed. Aside from 2DMs, this approach is also appropriate for other types of materials such as Au, α-Si, and Al2O3. Its flexibility and IC-compatibility allow our strain lithography methodology promising in accelerating the potential applications of 2DMs in extensive fields ranging from nanoelectromechanical systems, high-performance sensing, and nontraditional photovoltaics to quantum information science.

Recent studies have shown that diamond field effect transistors (FETs) have great potential in high-power and high-frequency electronics, exhibiting the maximum leakage current of 1.35 A.mm(-1) and the breakdown voltage of 2 kV. However, there is still a lack of preliminary exploration on diamond FETs with a three-dimensional (3D) architecture, which has been evidenced as a promising approach to increase device performance and density for silicon transistors. In this paper, we present a systematic investigation of 3D vertical gate-all-around (GAA) diamond transistors, combined with numerical simulation, device fabrication and characterization of device performance. The p-type conductivity of the diamond channel in a transistor is obtained by Boron-ion implantation. Our numberical simulations address the close correlation of transfer characteristics of the 3D vertical GAA diamond transistors with the ion implanted impurities. In the device fabrication, we introduce the focused ion and electron beam technology for the electrode interconnections in the 3D devices. Finally, we demonstrate that the 3D vertical GAA diamond transistor exhibits the on-off ratio of 2.5 x 10(3), subthreshold swing of 334.3 mV.dec-1, and threshold voltage of 0.64 V. And the temperature dependence of transfer characteristics of the 3D devices indicates that 3D vertical GAA diamond transistors have potential application prospects in extreme envi-ronments such as high temperature.

Bidirectional Origami In article number 2200373, Changzhi Gu, Junjie Li, and co-workers demonstrate bidirectional origami based on focused ion beam (FIB)-induced stress for various of materials, and the Monte Carlo simulations show that the key factor of bidirectional origami relies on the sputtering ratio for materials. Furthermore, a 3D chiral metasurface composed of bidirectional folded split ring resonators is designed and fabricated to realize a giant circular dichorism of 0.78/0.85 (Experiment/Simulation).

Three-dimensional (3D) vertical architecture transistors represent an important technological pursuit, which have distinct advantages in device integration density, operation speed, and power consumption. However, the fabrication processes of such 3D devices are complex, especially in the interconnection of electrodes. In this paper, we present a novel method which combines suspended electrodes and focused ion beam (FIB) technology to greatly simplify the electrodes interconnection in 3D devices. Based on this method, we fabricate 3D vertical core-double shell structure transistors with ZnO channel and Al 2 O 3 gate-oxide both grown by atomic layer deposition. Suspended top electrodes of vertical architecture could be directly connected to planar electrodes by FIB deposited Pt nanowires, which avoid cumbersome steps in the traditional 3D structure fabrication technology. Both single pillar and arrays devices show well behaved transfer characteristics with an I on / I off current ratio greater than 10 6 and a low threshold voltage around 0 V. The ON-current of the 2 × 2 pillars vertical channel transistor was 1.2 μA at the gate voltage of 3 V and drain voltage of 2 V, which can be also improved by increasing the number of pillars. Our method for fabricating vertical architecture transistors can be promising for device applications with high integration density and low power consumption.

In this article, the normally- OFF etching-free p-GaN stripe array gate AlGaN/GaN high-electron-mobility-transistors (PSAG-HEMTs) are designed and experimentally demonstrated through hydrogen plasma treatment. The unique threshold voltage ( ${V}_{TH}$ ) modulation technique based on the PSAG structure is proposed and simulated. Using this method, the ${V}_{TH}$ can be continuously shifted from −0.14 to +1.03 V by just tuning the widths of p-GaN ( ${W}_{p}$ ) and hydrogenated p-GaN (HR-GaN) stripes. To improve breakdown voltage (BV), the PSAG is extended to the drain side based on the 3-D simulation results so that a new electric-field peak is introduced at the edge of the PSAG in the drain side and then the surface electric field is optimized. Besides this, an enhanced conductivity effect is observed and results in a low ON-resistance. The fabricated PSAG-HEMT with $0.75~\mu \text{m}~{W}_{p}$ and 4- $\mu \text{m}$ extension length ( ${L}_{E}$ ) exhibits a positive ${V}_{TH}$ of +0.8 V, a low specific ON-resistance ( ${R}_{\text {ON,sp}}$ ) of 2.73 $\text{m}\Omega \cdot cm^{2}$ , a high BV of 852 V (1449 V) at ${I}_{D} = 1 ~\mu \text{A}$ /mm, and BFOM of 266 MW/cm2 (769 MW/cm2) with substrate grounded (floating), which demonstrate significant improvements over Reference single-gate E-mode and D-mode devices. This work provides a promising architecture for future high voltage normally- OFF p-GaN HEMT devices.

In this paper, a novel laterally coupled p-GaN gate (LCPG) structure have been implemented by the selectively hydrogen plasma treatment to fabricate GaN-on-Si HEMTs with a high breakdown voltage (BV) and a low ON-resistance (R-ON). Due to the coupled effect inside the LCPG, the 2DEG under the gate structure is depleted. The effect of different p-GaN to drain spacing (Lp-D) on device performance is studied.

In this work, p-type polarization-induced doping (PID) recessed-gate p-channel InGaN/GaN/AlGaN heterostructure field-effect transistors (HFETs) are proposed. It is found that the current density of the device can be increased by introducing an InGaN/GaN/AlGaN heterojunction and p-type PID. The simulation results show that the current density can apparently be increased (from 3.42 mA mm−1 to 7.31 mA mm−1) due to the increased hole concentration introduced by the InGaN/GaN/AlGaN heterojunction and the p-type PID. Different threshold voltages can be obtained by adjusting the GaN channel thickness, and normally-off p-channel HFETs with a negative V TH of −1 V were produced when a 6 nm GaN channel thickness was retained. These results may provide some reference information for the design of E-mode high-performance p-channel GaN devices.

As an inherent characteristic of light, polarization plays important roles in information storage, display and even encryption. Metasurfaces, composed of specifically designed subwavelength units in a two-dimensional plane, offer a great convenience for polarization manipulation, yet improving their integrability and broadband fidelity remain significant challenges. Here, based on the combination of various subwavelength cross-nanofins (CNs), a new type of metasurface for multichannel hybrid polarization distribution in near-field is proposed. Sub-wavelength CN units with various waveplate (WP) functionalities, such as frequency-division multiplexing WP, half-WP and quarter-WP are implemented with high efficiency in broadband. High-resolution grayscale image encryption, multi-image storage and rapid polarization detection are demonstrated by encoding the WP pixels into single, double and four channels, respectively. All these applications possess good fidelity in an ultrabroad wavelength band from 1.2 to 1.9 µm, and the high degree of integrability, easy fabrication and multifunction make the CN-shaped WP pixels a promising candidate in optical device miniaturization, quantum applications and imaging technologies.

D-mode and fully recessed E-mode GaN-based MIS-HEMTs using atomic layer deposition (ALD) hafnium oxide (HfO2) as gate dielectric were fabricated on Si substrates. Threshold voltage hysteresis $(\Delta V_{th})$ of the D-mode sample was reduced from 1.11 V to 0.42V after post-gate-annealing (PGA) at the temperature of 400°C in the nitrogen atmosphere for 5 minutes. This phenomenon can be explained by the reduction of interface-state density (from $8.96\times 10^{12}-1.2\times 10^{14}\text{eV}^{-1}\cdot \text{cm}^{-2}$ to $2.6\times 10^{12}-7.6\times 10^{13}\text{eV}^{-1}\cdot \text{cm}^{-2})$. By contrasting the $\Delta V_{th}$ of the D-mode sample and the E-mode sample after PGA, it was found that $\text{AlGaN}/\text{AIN}$ barrier of D-mode sample could limit electron flux to the interface, leading to its threshold voltage hysteresis being smaller than that of the E-mode sample.

Herein, the mechanism of increased gate leakage current observed in SiN x ‐passivated high‐resistivity cap layer high‐electron‐mobility transistors (HRCL‐HEMTs) is investigated. The leakage is found to be correlated with the roughened morphology and deviated surface stoichiometry caused by H‐plasma treatment. An additional step of surface etching before passivation restores GaN surface and gate leakage is reduced by about two orders of magnitude, whereas the other electrical characteristics of p‐GaN HEMTs are preserved.

p-doped gallium nitride (GaN) regrowth by epitaxial lateral overgrowth using a SiO2 mask is studied. A comparison between SiO2 and Al2O3 masked p-GaN by cathodoluminescence spectroscopy and scanning electron microscopy indicates that donor-type impurities are related to the SiO2 mask. A domain peak of 3.25 eV induced by shallow-donor and acceptor transitions and the dark contrast of obtuse triangles have been detected in SiO2 masked p-type GaN. Secondary ion mass spectroscopy is simultaneously employed for the analysis of SiO2 and Al2O3 masked p-GaN and identifies that the source of donor-type impurities is from Si atoms. Furthermore, the experimental results of cross-sectional microstructures at different regrowth times have been investigated. It is found that the donor-type impurities tend to cluster in semi-polar 112¯2 facets before the coalescence at the bottom of adjacent triangular stripes starts. The explanation for the non-uniform distribution of impurities is that semi-polar 112¯2 facets exhibit more dangling bond densities than the (0001) plane, and the SiO2 mask exposed to the vapor phase would likely introduce more impurities before the coalescence of GaN stripes.

Wuliangsuhai Lake, as a typical shallow lake in Hetao irrigation district, is located in Northern China. We took sediment samples in spring, summer, autumn, and winter, respectively. The total arsenic (As), total mercury (Hg) and other parameters (temperature, pH, EC, particle size of sediments and organic matter in sediments) were measured. Based on the temporal variations, seasonal comparisons and factor analysis, the following conclusions were obtained. (1) The seasonal characteristics of Hg and As were: summer > spring > autumn > winter, and spring > summer > autumn > winter. (2) The higher concentration of Hg and As during summer was considered to be caused by the higher organic matter and humus content, which made heavy metals strongly adsorbed and complexed, and changes in the organic matter content would enhance the binding state of the less active organic matter then deposit in sediment. (3) The speciation of mercury and arsenic was also the reason, in summer, the Hg-0 in the atmosphere was oxidized to Hg2+, entering into water through rainwater washing and dry deposition; then, soluble Hg2+ was quickly adsorbed and fixed in sediment, a series of transformations reduces its activity. The As3+ would be oxidized to As5+ which would form precipitated. Therefore, the content of Hg and As, environmental risk and potential ecological risk of mercury in sediments were higher in summer.

The hydrogen plasma treatment of single crystal diamond was carried out by microwave plasma chemical vapor deposition equipment, and the normally-off hydrogen-terminated diamond field-effect transistors (FETs) with different gate lengths were prepared by atomic layer deposition (ALD) which deposited HfO2 as gate oxide. We systematically investigated the influence of hydrogen treatment duration, gate length, channel length and gate oxide material HfO2 on the hydrogen-terminated diamond FETs. Results show that the HfO2 gate oxide allows the fabricated FETs to exhibit a normally-off characteristic, which is advantageous for the practical application of power devices. The drain-source current, threshold voltage, subthreshold swing, and I-on/I-off of the fabricated diamond FETs with gate length of 5 mu m are 11 mA/mm, -2.9 V, 3 mS/mm, and 10(6), respectively. With the increase of the gate length (L-g = 5 mu m, 20 mu m, 50 mu m), the drain current density, threshold voltage, and transconductance of the devices decrease, which is due to the higher channel resistance and inhomogeneity of the hydrogen surface termination.

Recently, β‐Ga2O3 and black phosphorus (BP) have attracted enormous attention as the solar‐blind ultraviolet (UV) and infrared (IR) photosensitive materials for next‐generation optoelectronic devices, respectively, due to their special bandgap and electrical characteristics. Many β‐Ga2O3‐based UV photodetectors and BP‐based IR photodetectors have been investigated separately, but there is no report on the heterojunction and photoelectric devices formed by these two excellent materials. Herein, metalorganic chemical vapor deposition (MOCVD) heteroepitaxial β‐Ga2O3 and BP pn heterojunction for solar‐blind UV and IR dual‐band photodetector is proposed and demonstrated for the first time. The device demonstrates a remarkable photoresponse under UV and IR irradiations with a responsivity of 88.5 and 1.24 mA W−1, respectively, clear pn heterojunction characteristics, as well as an excellent photoswitch periodicity. Moreover, under different irradiation conditions, the photoelectric properties of β‐Ga2O3/BP pn heterojunction, including their photogeneration and photoresponse, are investigated in detail. These results signify that β‐Ga2O3/BP pn heterojunction may find potential applications in future UV/IR dual‐band detection systems.

In this paper, we have proposed a method of O plasma treatment before gate metal deposition to increase the threshold voltage for p-GaN gate HEMTs. The technique of O plasma treatment is an in-situ method. The threshold voltage (Vth) was shifted from 1.27 V to 1.81 V after O plasma treatment, which may be caused by partly oxidation of p-GaN. The other characteristics of devices like drain current, gate breakdown and gate control were not degraded after the surface O plasma treatment. In addition, the devices with O plasma treatment have a better thermal stability.

We investigate the performance of AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) by inserting a fluorinated graphene insulator. It is found that the interface-state density of the sample with fluorinated graphene (5.8 x 10(13)-8.7 x 10(11) eV(-1)-cm(-2)) was lower than that without fluorinated graphene (1.1 x 10(14)-8.1 x 10(12) eV(-1)-cm(-2)) and exhibits better properties, including higher saturation drain current (I-sat), lower on-resistance (R-on), smaller hysteresis of threshold voltage (Delta V-th), and better current collapse suppression. Furthermore, the inserted fluorinated graphene could increase the activation energy of surface leakage current, which is verified by the analysis of leakage current. Our results suggest that the fluorinated graphene insulator can lessen interface-state density at the shallow energy levels by the interface-state density decrement and the activation energy increment.

The spatially continuous control of the physical properties in semiconductor materials is an important strategy in increasing electron-capturing or light-harvesting efficiencies, which is highly desirable for the application of optoelectronic devices including photodetectors, solar cells and biosensors. Unlike the multi-layer growth of chemical composition modulation, local strain offers a convenient way to continuously tune the physical properties of a single semiconductor layer, and open up new possibility for band engineering within the 2D plane. Here, we demonstrate that the gradient refractive index and bandgap can be generated in atomically thin transition metal dichalcogenide flakes due to the effect of thermal strain difference. A highly resolved confocal scanning optical microscopy is used to perform a real-space light-reflection mapping of suspended atomically thin WSe2 flakes at the low temperature of 4.2 K, in which the parabolic light-reflection profiles have been observed on suspended monolayer and bilayer WSe2 flakes. This finding is corroborated by our theoretical model which includes the effect of strain on both the refractive index and bandgap of nanostructures. The inhomogeneous local strain observed here will allow new device functionalities to be integrated within 2D layered materials, such as in-plane photodetectors and photovoltaic devices.