jinzhitong

A supercapacitor comprising tungsten disulfide and polyaniline is assembled, exhibiting excellent electrochemical properties in high frequencies. In particular, high areal capacitance, low resistance, and short relaxation time are recorded at 120 Hz, the conventional alternating current (AC) frequency, underscoring the potential of the device for AC line filtering applications.

Abstract

Transition metal dichalcogenides are considered promising constituents in energy storage devices due to their large surface areas, 2D sheet structures, and occurrence of efficient redox reactions at their surfaces. Supercapacitors comprising WS₂-polyaniline (PANI) composite electrodes which exhibit excellent electrochemical properties, particularly effective high frequency response, are constructed. The highly porous WS₂-PANI device facilitate rapid ion transport and surface access, aiding rapid reversible redox reactions contributing to the high frequency pseudocapacitive profile of the device. The symmetric WS₂-PANI supercapacitor displays significantly higher capacitance of 180 µF cm⁻² at a frequency of 120 Hz. This study points to potential application of WS₂ composites in high frequency applications such as alternating current line filtering, and may open new avenues for employing the material in energy storage applications.

Advanced Electronic Materials, Volume 7, Issue 5, May 2021.

This work reports a PdSe₂-based gate-controlled rectifier diode realized simply by creating the lateral heterojunction using as-exfoliated PdSe₂ flake composed of different thickness regions. Interestingly, by tailoring the heterojunction architecture with a certain combination of the thicknesses, a unique gate-controlled rectification can be observed where the rectifying direction can be tuned by the applied gate bias.

Abstract

The thickness-dependent band structure of 2D materials has enabled the construction of in-plane lateral heterojunction within the same material platform. Simply forming regions of the same 2D material with different thicknesses induces the band offsets in energy bands at the interface to complete the heterojunction. Especially, pentagonal palladium diselenide (PdSe₂) can create various combinations of different band gaps due to its widely tunable band gap ranging from 0 to ≈1.3 eV. Here, a PdSe₂-based gate-controlled rectifier diode realized simply by creating the lateral heterojunction using as-exfoliated PdSe₂ flake composed of different thickness regions are reported. Interestingly, by tailoring the heterojunction architecture with a certain combination of the thicknesses, a unique gate-controlled rectification can be observed where the rectifying direction can be tuned by the applied gate bias. The different gate modulation levels in the thin and thick regions leads to the different band bending, respectively. Therefore, adjusting the heterojunction barrier height by the gate bias makes it possible to modulate the direction of dominant current. The demonstration of the reversible rectifying direction paves the way for the realization of essential component in the tunable logic gate.

Inch-scale, uniform monolayer MoSe₂ films are obtained within 5 min using a spin-coating based, NaCl-assisted chemical vapor deposition method. As-grown monolayer MoSe₂ films exhibit large grains, high crystal quality, and good electronic transport properties. The method is also applicable to obtain monolayer MoS₂, WS₂, and WSe₂ Films.

Abstract

The large-scale growth of semiconducting thin films on insulating substrates enables batch fabrication of atomically thin electronic and optoelectronic devices and circuits without film transfer. Here an efficient method to achieve rapid growth of large-area monolayer MoSe₂ films based on spin coating of Mo precursor and assisted by NaCl is reported. Uniform monolayer MoSe₂ films up to a few inches in size are obtained within a short growth time of 5 min. The as-grown monolayer MoSe₂ films are of high quality with large grain size (up to 120 µm). Arrays of field-effect transistors are fabricated from the MoSe₂ films through a photolithographic process; the devices exhibit high carrier mobility of ≈27.6 cm² V^–1 s^–1 and on/off ratios of ≈10⁵. The findings provide insight into the batch production of uniform thin transition metal dichalcogenide films and promote their large-scale applications.

Recent advances in obtaining large-area 2D transition metal chalcogenides by various methods are first highlighted, with their advantages and disadvantages evaluated. Then, strategies for the control of important factors in material growth are discussed. Applications of the materials in electronics, optoelectronics, spintronics, etc., are also introduced. Finally, ideas and prospects for the future developments of wafer-scale 2D transition metal chalcogenides are provided.

Abstract

2D transition metal chalcogenides (TMCs) have attracted tremendous interest from both the scientific and technological communities due to their variety of properties and superior tunability through layer number, composition, and interface engineering. Wafer-scale production of 2D TMCs is critical to the industrial applications of these materials. Extensive efforts have been bestowed to the large-area growth of 2D TMCs through various approaches. In this review, recent advances in obtaining large-area 2D TMCs by different methods such as chemical vapor deposition (CVD), metal–organic CVD, and physical vapor deposition are first highlighted and their advantages and disadvantages are also evaluated. Then, strategies for the control of the grains, morphology, layer number, and phase to achieve controllable and uniform thicknesses and large crystal domains for 2D TMCs are discussed. Applications of large-area 2D TMCs in electronics, optoelectronics, spintronics, etc., are also introduced. Finally, ideas and prospects for the future developments of wafer-scale 2D TMCs are provided.

Magneto-LC resonance experiments and density functional calculations demonstrate light-mediated room temperature ferromagnetism in V-WS₂ monolayers. This phenomenon is attributed to the presence of excess holes in the conduction and valence bands, as well as carriers trapped in the magnetic doping states, which mediates the magnetization of the V-WS₂ monolayer. These findings potentially establish a new subfield named photo-spintronics.

Abstract

Atomically thin transition metal dichalcogenide (TMD) semiconductors hold enormous potential for modern optoelectronic devices and quantum computing applications. By inducing long-range ferromagnetism (FM) in these semiconductors through the introduction of small amounts of a magnetic dopant, it is possible to extend their potential in spintronics. Here, light-mediated, room temperature (RT) FM, in V-doped WS₂ (V-WS₂) monolayers is demonstrated. The authors probe this effect using the principle of magnetic LC resonance, which employs a soft ferromagnetic Co-based microwire coil driven near its resonance in the radio frequency regime, where it is highly sensitive to changes in magnetic flux. They use this to measure the magnetic permeability of the V-WS₂ monolayer subject to light illumination. Notably, the magnetic permeability of the monolayer is found to depend on the laser intensity, thus confirming light control of RT magnetism in this material. Guided by density functional theory calculations, they attribute this phenomenon to the presence of excess holes in the conduction and valence bands, as well as carriers trapped in the magnetic doping states, which mediates the magnetization of the V-WS₂ monolayer. These findings provide a unique route to exploit light-controlled ferromagnetism at RT and potentially establish a new subfield named photo-spintronics.

The authors demonstrate air-stable, inkjet-printed n-type molybdenum disulfide (MoS₂) and p-type indacenodithiophene-co-benzothiadiazole (IDT-BT) field-effect transistors (FETs) with a mobility >0.1 cm² V⁻¹ s⁻¹ and an I _on/I _off ratio of ≈ 10³. The integrated FETs enable inkjet-printed logic inverters operating at low voltage with a voltage gain |A _v| ≈ 4 and microsecond switching times. This represents a fundamental step towards enabling low-cost printed and stable integrated circuits.

Abstract

Air-stable semiconducting inks suitable for complementary logic are key to create low-power printed integrated circuits (ICs). High-performance printable electronic inks with 2D materials have the potential to enable the next generation of high performance low-cost printed digital electronics. Here, the authors demonstrate air-stable, low voltage (<5 V) operation of inkjet-printed n-type molybdenum disulfide (MoS₂), and p-type indacenodithiophene-co-benzothiadiazole (IDT-BT) field-effect transistors (FETs), estimating an average switching time of τ_MoS2 ≈ 4.1 μs for the MoS₂ FETs. They achieve this by engineering high-quality MoS₂ and air-stable IDT-BT inks suitable for inkjet-printing complementary pairs of n-type MoS₂ and p-type IDT-BT FETs. They then integrate MoS₂ and IDT-BT FETs to realize inkjet-printed complementary logic inverters with a voltage gain |A _v| ≈ 4 when in resistive load configuration and |A _v| ≈ 1.4 in complementary configuration. These results represent a key enabling step towards ubiquitous long-term stable, low-cost printed digital ICs.

Semiconductor alloys are usually associated with spatial compositional fluctuations which affect a material's in-plane transport properties. This alloy disorder is observed in a ternary Mo_0.3W_0.7Se₂ monolayer, showing a non-monotonous temperature dependence of the luminescence Stokes shift, S-shape; a feature not evident in its binary counterparts. Experiments and simulations suggest an exponential energy shape for the density of localized states.

Abstract

Alloying semiconductors is often used to tune the material properties desired for device applications. The price for this tunability is the extra disorder caused by alloying. In order to reveal the features of the disorder potential in alloys of atomically thin transition-metal dichalcogenides (TMDs) such as Mo _x W_1−x Se₂, the exciton photoluminescence is measured in a broad temperature range between 10 and 200 K. In contrast to the binary materials MoSe₂ and WSe₂, the ternary system demonstrates non-monotonous temperature dependences of the luminescence Stokes shift and of the luminescence linewidth. Such behavior is a strong indication of a disorder potential that creates localized states for excitons and affects the exciton dynamics responsible for the observed non-monotonous temperature dependences. A comparison between the experimental data and the results obtained by Monte Carlo computer simulations provides information on the energy scale of the disorder potential and also on the shape of the density of localized states created by disorder. Statistical spatial fluctuations in the distribution of the chemically different material constituents are revealed to cause the disorder potential responsible for the observed effects. A deeper understanding of the disorder-induced effects is vital for prospective TMD alloy-based devices.

Nature Electronics, Published online: 17 May 2021; doi:10.1038/s41928-021-00573-1

Heterophase grain boundaries in memristors based on pentagonal palladium diselenide can guide the formation of conductive filaments during resistive switching, leading to devices with uniform switching properties, low set voltages, long retention times and programmable multilevel resistance states.

Nature Electronics, Published online: 10 May 2021; doi:10.1038/s41928-021-00569-x

Disorder in the charge carrier transport of graphene-based field-effect transistors can be used to construct physically unclonable functions that are secure and can withstand advanced computational attacks.

Author(s): Xiang-Pei Liu, Xing-Can Yao, Youjin Deng, Xiao-Qiong Wang, Yu-Xuan Wang, Chun-Jiong Huang, Xiaopeng Li, Yu-Ao Chen, and Jian-Wei Pan

Vortices play a leading role in many fascinating quantum phenomena. Here we generate a large number of vortices by thermally quenching a fermionic superfluid of Li6 atoms in an oblate optical trap and study their annihilation dynamics and spatial distribution. Over a wide interaction range from the ...

[Phys. Rev. Lett. 126, 185302] Published Thu May 06, 2021

Nature Nanotechnology, Published online: 06 May 2021; doi:10.1038/s41565-021-00887-3

Graphene promises long-distance transfer of spin information with concomitant high charge carrier mobility. Proximity coupling of bilayer graphene with the 2D interlayer antiferromagnetic CrSBr now enables active generation of spin currents in graphene both electrically and thermally.

Nature Materials, Published online: 10 May 2021; doi:10.1038/s41563-021-01001-7

Centimetre-scale growth of few-layer black phosphorous with high crystalline quality and homogeneity is realized by pulsed laser deposition.

Nature Chemistry, Published online: 10 May 2021; doi:10.1038/s41557-021-00678-2

Open-shell nanographenes are promising for quantum technologies, but their magnetic stability has remained limited by weak exchange coupling. Now, two large rhombus-shaped nanographenes with zigzag peripheries, one with 48 carbon atoms and the other with 70, have been synthesized on gold and copper surfaces. The 70-carbon compound exhibits a large magnetic exchange coupling exceeding 100 meV.

Nature, Published online: 12 May 2021; doi:10.1038/s41586-021-03472-9

Electric contacts of semimetallic bismuth on monolayer semiconductors are shown to suppress metal-induced gap states and thus have very low contact resistance and a zero Schottky barrier height.

Nature Materials, Published online: 06 May 2021; doi:10.1038/s41563-021-00979-4

The optically detected magnetic resonance of a single defect in hexagonal boron nitride is reported.