MoS2-Based Photodetectors Powered by Asymmetric Contact Structure with Large Work Function Difference

Self-powered devices are widely used in the detection and sensing fields.Asymmetric metal contacts provide an effective way to obtain self-powered devices.Finding two stable metallic electrode materials with large work function differences is the key to obtain highly efficient asymmetric metal contacts structures.However,common metal electrode materials have similar and high work functions,making it difficult to form an asymmetric contacts structure with a large work function difference.Herein,Mo2C crystals with low work function(3.8 eV) was obtained by chemical vapor deposition(CVD) method.The large work function difference between Mo2C and Au allowed us to synthesize an efficient Mo2C/MoS2/Au photodetector with asymmetric metal contact structure,which enables light detection without external electric power.We believe that this novel device provides a new direcfor the design of miniature self-powered photodetectors.These results also highlight the great potential of ultrathin Mo2C prepared by CVD in heterojunction device applications.

Study of structure-property relationship of semiconductor nanomaterials by off-axis electron holography

As the scaling down of semiconductor devices, it would be necessary to discover the structure-property relationship of semiconductor nanomaterials at nanometer scale. In this review, the quantitative characterization technique off-axis electron holography is introduced in details, followed by its applications in various semiconductor nanomaterials including group IV, compound and two-dimensional semiconductor nanostructures in static states as well as under various stimuli. The advantages and disadvantages of off-axis electron holography in material analysis are discussed, the challenges facing in-situ electron holographic study of semiconductor devices at working conditions are presented, and all the possible influencing factors need to be considered to achieve the final goal of fulfilling quantitative characterization of the structure-property relationship of semiconductor devices at their working conditions.

Flexible and highly-sensitive pressure sensor based on controllably oxidized MXene

Conductive Ti_(3)C_(2)T_(x)MXenes have been widely investigated for the construction of flexible and highly-sensitive pressure sensors.Although the inevitable oxidation of solution-processed MXene has been recognized,the effect of the irreversible oxidation of MXene on its electrical conductivity and sensing properties is yet to be understood.Herein,we construct a highly-sensitive and degradable piezoresistive pressure sensor by coating Ti_(3)C_(2)T_(x)MXene flakes with different degrees of in situ oxidation onto paper substrates using the dipping-drying method.In situ oxidation can tune the intrinsic resistance and expand the interlayer distance of MXene nanosheets.The partially oxidized MXene-based piezoresistive pressure sensor exhibits a high sensitivity of 28.43 kPa^(-1),which is greater than those of pristine MXene,over-oxidized MXene,and state-of-the-art paper-based pressure sensors.Additionally,these sensors exhibit a short response time of 98.3 ms,good durability over 5000 measurement cycles,and a low force detection limit of 0.8 Pa.Moreover,MXene-based sensing elements are easily degraded and environmentally friendly.The MXene-based pressure sensor shows promise for practical applications in tracking body movements,sports coaching,remote health monitoring,and human–computer interactions.

Maximizing the ion accessibility and high mechanical strength in nanoscale ion channel MXene electrodes for high-capacity zinc-ion energy storage

Two-dimensional transition-metal carbides(MXenes)have superhydrophilic surfaces and superior metal conductivity,making them competitive in the field of electrochemical energy storage.However,MXenes with layered structures are easily stackable,which reduces the ion accessibility and transport paths,thus limiting their electrochemical performance.To fully exploit the advantages of MXenes in electrochemical energy storage,this study reports the etching of large-sized MXene into nanosheets with nanoscale ion channels via a chemical oxidation method.While the resulting ion-channel MXene electrodes retain the excellent mechanical strength and electrical conductivity of large-sized MXene nanosheets,they can effectively shorten the ion transport distance and improve the overall electrochemical activity.The fabricated self-healing MXene-based zinc-ion microcapacitor exhibits a high areal specific capacitance(532.8 mF cm^(-2))at the current density of 2mA cm^(-2),a low self-discharge rate(4.4 mV h^(-1)),and high energy density of 145.1μWh cm^(-2)at the power density of 2800μW cm^(-2).The proposed nanoscale ion channel structure provides an alternative strategy for constructing high-performance electrochemical energy storage electrodes,and has great application prospects in the fields of electrochemical energy storage and flexible electronics.

3D Porous MXene Aerogel through Gas Foaming for Multifunctional PressureSensor

The development of smart wearable electronic devices puts forward higher requirements for future flexible electronics. The design of highly sensitive and high-performance flexible pressure sensors plays an important role in promoting the development of flexible electronic devices. Recently, MXenes with excellent properties have shown great potential in the field of flexible electronics. However, the easy-stacking inclination of nanomaterials limits the development of their excellent properties and the performance improvement of related pressure sensors. Traditional methods for constructing 3D porous structures have the disadvantages of complexity, long period, and difficulty of scalability. Here, the gas foaming strategy is adopted to rapidly construct 3D porous MXene aerogels. Combining the excellent surface properties of MXenes with the porous structure of aerogel, the prepared MXene aerogels are successfully used in high-performance multifunctional flexible pressure sensors with high sensitivity (306 kPa^(-1)), wide detection range (2.3 Pa to 87.3 kPa), fast response time (35 ms), and ultrastability (>20,000 cycles), as well as self-healing, waterproof, cold-resistant, and heat-resistant capabilities. MXene aerogel pressure sensors show great potential in harsh environment detection, behavior monitoring, equipment recovery, pressure array identification, remote monitoring, and human-computer interaction applications.

Study of the growth mechanism of a self‑assembled and ordered multi‑dimensional heterojunction at atomic resolution

Multi-dimensional heterojunction materials have attracted much attention due to their intriguing properties,such as high efciency,wide band gap regulation,low dimensional limitation,versatility and scalability.To further improve the performance of materials,researchers have combined materials with various dimensions using a wide variety of techniques.However,research on growth mechanism of such composite materials is still lacking.In this paper,the growth mechanism of multidimensional heterojunction composite material is studied using quasi-two-dimensional(quasi-2D)antimonene and quasione-dimensional(quasi-1D)antimony sulfde as examples.These are synthesized by a simple thermal injection method.It is observed that the consequent nanorods are oriented along six-fold symmetric directions on the nanoplate,forming ordered quasi-1D/quasi-2D heterostructures.Comprehensive transmission electron microscopy(TEM)characterizations confrm the chemical information and reveal orientational relationship between Sb2S3 nanorods and the Sb nanoplate as substrate.Further density functional theory calculations indicate that interfacial binding energy is the primary deciding factor for the self-assembly of ordered structures.These details may fll the gaps in the research on multi-dimensional composite materials with ordered structures,and promote their future versatile applications.