Interfacial Distance Research Articles

Vacancy Assisted Bilayer Graphene Contact for Monolayer Graphene Channel Devices

Contact engineering of monolayer graphene channel FETs has been a fundamental limiting factor hindering its intrinsic benefits for applications such as THz electronics, quantum sensing, quantum computing/communication devices, etc. This experimental work presents a unique technique to achieve record low contact resistance using carbon vacancy-assisted bilayer graphene contact. The bilayer graphene contact with engineered carbon vacancies lowered the metal-graphene interfacial distance and enhanced the atomic orbital overlap, eventually lowering the contact resistance. The interfacial properties and orbital interactions are investigated using density functional theory and non equilibrium Green’s function based transport computations. The reduction in contact resistance is then experimentally validated using unique Kelvin probe structures with monolayer and bilayer contacts. The captured contact resistance is as low as ~36 Ω.μm, which is a record low contact resistance value reported to date.

Coaxial Graphene/MXene Microfibers with Interfacial Buffer-Based Lightweight Distance Sensors Assisting Lossless Grasping of Fragile and Deformable Objects.

Lossless and efficient robotic grasping is becoming increasingly important with the widespread application of intelligent robotics in warehouse transportation, human healthcare, and domestic services. However, current sensors for feedback of grasping behavior are greatly restricted by high manufacturing cost, large volume and mass, complex circuit, and signal crosstalk. To solve these problems, here, we prepare lightweight distance sensor-based reduced graphene oxide (rGO)/MXene-rGO coaxial microfibers with interface buffer to assist lossless grasping of a robotic manipulator. The as-fabricated distance microsensor exhibits a high sensitivity of 91.2 m-1 in the distance range of 50-300 μm, a fast response time of 116 ms, a high resolution of 5 μm, and good stability in 500 cycles. Furthermore, the high-performance and lightweight microsensor is installed on the robotic manipulator to reflect the grasp state by the displacement imposed on the sensor. By establishing the correlation between the microsensing signal and the grasp state, the safe, non-destructive, and effective grasp and release of the target can be achieved. The lightweight and high-powered distance sensor displays great application prospects in intelligent fetching, medical surgery, multi-spindle automatic machines, and cultural relics excavation.

Computational Analysis of Metal Contact on Bi2O2Se with Se Surface Vacancies

AbstractIn this work, a theoretical study on the electronic properties of the metal/Bi2O2Se interface is presented through the density functional theory calculation. Particularly, the effects of Cr, Pd, Pt, Au, and Bi on monolayer, bilayer, and trilayer Bi2O2Se are explored. Naturally created Se vacancies on the Bi2O2Se surface are also considered by constructing two interface structures: the metal/Bi2O2Se with the Se vacancies remaining or filled with metals. For the metal/monolayer Bi2O2Se, it is observed that the Bi2O2Se layer is fully metallized since Bi2O2Se strongly interacts with the metal. Meanwhile, for the metal/bilayer and trilayer Bi2O2Se, the Bi2O2Se layers remain semiconducting except for the layer right next to metal. Among the considered metals, regardless of whether the Se vacancies are filled with metal or not, the semiconducting layers in bilayer and trilayer Bi2O2Se form Ohmic contact with Bi. It is also found that filling the Se vacancies with the metals heavier than Se increases the interface distance between metal and Bi2O2Se, and hence results in the weak Fermi level pinning effect.

Role of Chalcogen Defect Introducing Metal-Induced Gap States and Its Implications for Metal-TMDs' Interface Chemistry.

The contact resistance of the transition metal dichalcogenide (TMD) devices is not comparable to that of their silicon counterparts, probably due to a lack of clarity in their interface chemistry. Looking beyond the conventional Schottky-Mott rule, the metal chalcogen orbital overlaps, tunnel barrier, and metal-induced gap states (MIGSs) are crucial factors determining different metals' contact properties with TMDs. Exploring their properties helps TMDs' contact resistance engineering, driven mainly by their orbital overlaps and perturbing parameters. This work presents the interface chemistry of TMDs (MoS2, MoSe2, WS2, and WSe2) with different metals (Au, Cr, Ni, and Pd) in detail using density functional theory computations. Additionally, the work discusses the role of the chalcogen vacancy and interstitial defects in the metal-TMD interactions and corresponding MIGS features. The investigations reveal that Au does not show any significant MIGS due to its weak interactions with all the TMDs. However, other investigated metals have a strong affinity with TMDs, making significant MIGS contributions. All the metals offer n-type doping characteristics to TMDs due to valence charge transfer from the metals toward TMDs. The chalcogen vacancy boosts the orbital overlaps of the TMDs with all the metals. The vacancy reduces metal-TMD interfacial distance, which can be a promising technique to reduce the tunnel barrier and contact resistance. The MIGS and defect-induced gap states (DIGSs) reflect the possibility of Fermi-level pinning in the TMDs' contacts with Cr, Ni, and Pd. Besides, the work discloses that the chalcogen vacancy converts an n-type Pd-TMD interface into p-type due to reverse charge transfer after the vacancy. Chalcogen interstitial impurity also helps with contact resistance engineering for some metal-TMD systems by reducing the bond distance of the metal TMDs. Our study highlights the possibility of defect-assisted and MIGS-based contact engineering at the metal-TMD interfaces.

Mechanism and optimum pressure for sliding-mode nanogenerator

Abstract Triboelectric nanogenerator has extensive applicability because of its capability of harvesting mechanical energy and flexible working modes. To research the optimum pressure and improve the recovered energy of the sliding-mode triboelectric nanogenerator, a contact model of the Al/PTFE tribo-pair is studied by ab initio calculation and finite element simulation. The F-atom of PTFE is proved to be the electron accepter and the charges transferred can be predicted by Bader charge analysis. The mathematical relation between interfacial distance, charges transferred and contact pressure can be fitted. By Gauss’s law, the electric field is simulated and the regeneration energy of the sliding-mode triboelectric nanogenerator can be evaluated by the total electric energy and friction loss. Finally, an optimum pressure can be set to the upper or lower limit of working pressure corresponding to larger recovered energy. And less friction coefficient and larger contact area are also effective methods for recovering energy.

A link to connect the friction properties calculated under constant load and constant interface distance models

A link to connect the friction properties calculated under constant load and constant interface distance models

Layer-dependent dielectric modulation in WS2/GaN heterostructures

Controlling over the electronic structure of two-dimensional (2D) semiconductors is crucial to unlock their full potential in the applications in future nanodevices. Here, we demonstrate a layer-dependent dielectric modulation of electronic structures in multilayer ${\mathrm{WS}}_{2}/\mathrm{GaN}$ heterostructures. The results investigated by means of in situ scanning tunneling microscopy/spectroscopy and photoluminescence spectroscopy show that the fluctuations of the dielectric environment induced by local corrugation of the GaN surface dramatically tune the band structure of monolayer ${\mathrm{WS}}_{2}$ with a large downshift of the valence band maximum by about 1.12 eV. Under the shielding effect of the first-layer ${\mathrm{WS}}_{2}$, the dielectric environment shows a weak modulation effect on the second-layer, and even has negligible influence on the third- and fourth-layer ${\mathrm{WS}}_{2}$. The relationship between dielectric environment and interfacial distance is further simulated through first-principles calculations. The electrostatic potential energy, differential charge densities, and charge transfer of the ${\mathrm{WS}}_{2}/\mathrm{GaN}$ heterostructure under different interfacial distances reveal that the differences of charge redistributions between the ${\mathrm{WS}}_{2}/\mathrm{GaN}$ interface and ${\mathrm{WS}}_{2}$ interlayer are responsible for the layer-dependent dielectric modulation. This work offers some references for the design and fabrication of novel 2D optoelectronic devices.

3D Minimum Channel Width Distribution in a Ni-Base Superalloy

The strength of a Ni-base superalloy depends strongly on its microstructure consisting of cuboidal {gamma }^{^{prime}} precipitates surrounded by narrow channels of gamma matrix. According to the theory of Orowan, a moving dislocation has to crimp through the minimal inter-precipitate spacing to admit the plastic deformation. We present a novel approach to evaluate the matrix channel width distribution of a matrix/{gamma }^{^{prime}} microstructure in binary representation. Our method relies on precise determination of the matrix/precipitate interfaces and requires no additional user input. For each matrix channel between two neighboring precipitates, we identify the minimal interface to interface distance vector with its length being the channel width. The performance of this method is demonstrated on the example of the commercial alloy CSMX-4. We show that, in contrast to conventional line sectioning approaches, the approach consistently handles experimental 2D micrographs and 3D phase-field simulation data. The identified distance vectors correlate to the underlying crystal symmetry independent of the image orientation. The obtained channel width distributions compare well between the 2D and 3D data. This is in terms of similar median and sigma of a log-normal distribution. The presented method overcomes limitations of the conventional line slicing approaches and provides a versatile tool for automated microstructure characterization.

Electronic transport in copper–graphene composites

We investigate electronic transport properties of copper–graphene (Cu–G) composites using a density-functional theory (DFT) framework. Conduction in composites is studied by varying the interfacial distance of copper/graphene/copper (Cu/G/Cu) interface models. Electronic conductivity of the models computed using the Kubo–Greenwood formula shows that the conductivity increases with decreasing Cu–G distance and saturates below a threshold Cu–G distance. The DFT-based Bader charge analysis indicates increasing charge transfer between Cu atoms at the interfacial layers and the graphene with decreasing Cu–G distance. The electronic density of states reveals increasing contributions from both copper and carbon atoms near the Fermi level with decreasing Cu–G interfacial distance. By computing the space-projected conductivity of the Cu/G/Cu models, we show that the graphene forms a bridge to the electronic conduction at small Cu–G distances, thereby enhancing the conductivity.

Tunable Schottky barrier of WSi2N4/graphene heterostructure via interface distance and external electric field

Improving the electric transport of field-effect transistors based on heterostructure (HTS) is a stern challenge by the reduction of the interfacial barrier. Herein, the electronic properties of WSi2N4/graphene HTS with different interface distance or external electric field are researched in detail using the first-principles approach. The result shows that a stable vdW HTS can be produced between WSi2N4 and graphene. In the interface, the tunable range of Schottky barrier height by external electric field exceeds that by interface distance, although both of two prominent approaches can modulate the energy band structures of WSi2N4/graphene HTSs. The transformation of Schottky contact from p-type to n-type, eventually into Ohmic contact can appear under external electric field. Predictably, the positive external electric field strength of 0.55 V·Å−1 can generate the largest carrier concentration 2.73 × 1013 cm−2 of graphene in the HTS. Verifiably, the redistribution of interface charge density determines the Schottky barrier height and contact type in the HTS. These findings present the potential of WSi2N4/graphene HTS as high sensitive Schottky field-effect transistors.

Atomic-structure and charge redistribution modified by intrinsic strain in α-fe/TMN (TM=Ti/Zr/Hf/V/Nb/Ta) interfaces

Metal/ceramics interfaces, ubiquitous in functional materials, alloys, and coatings/films systems, provide excellent mechanical and chemical properties, mainly originating from atomic structures and charge distribution at the hetero-interfaces. In the present work, the α-Fe/TMN (TM = Ti/Zr/Hf/V/Nb/Ta) interfaces were chosen as the typical metal/ceramic candidates to explore the atomic structures and electronic properties at such types of heterostructures. After full optimization, the relaxed models kept the stacking sequence OT (on top) of FeN, producing a slight difference in interfacial distance ( Δz ). Furthermore, a significant charge transfer emerged in interfacial Fe and N atoms, indicative of the stronger bond strength across the interfaces obtained from the analysis of planar-averaged charge density difference, PDOS, charge density and difference, partial charge density and ELF . Moreover, the increasing gain of interfacial N1 atoms and enhanced overlap of Fe and TM1 atoms could account for the higher adhesion strength of Fe/TMN. Finally, the amount of charge transfer for interfacial Fe1 was tiny compared to that of inner Fe4 atoms based on the Bader charge analysis, indicative of insignificant variation of interfacial ionicity. However, the magnetic moment (in μ B ) of interfacial Fe1 changed significantly compared to Fe4 atoms, indicating the charge redistribution, which enhanced the hybridization of N1- p and TM1- d states. One can conclude that the enhanced interfacial bonding strength could be ascribed to the strengthened hybridization of interfacial Fe1- d and N1- p covalence. These findings are relevant for a better comprehension of these specific configurations and improving technological modification of such kind of metal/ceramic system. • The relaxed interfacial models kept the stacking sequence of Fe–N (on top) OT. • The significant charge transfer results in the stronger bond strength across the interfaces. • The enhanced overlap of interfacial atoms account for the higher adhesion strength. • The magnetic moment of interfacial Fe1 changed significantly in comparison to that of Fe4 atoms.

Method for Detecting Electrical Interface in Sea Area Based on Active Electric Field

To obtain the direction and distance of the electrical interface in the sea, the active electric field of the electric dipole and two three-component electric field intensity sensors are used to detect them. First, the structure design of the active electric field detection device is given, and then a method for active electric field detection of the electrical interface in the sea area is proposed, that is, the effect of the electrical interface on the active electric field is equivalent to the effect of the mirror electric dipole, locating the position of the mirror dipole can be done by measuring the change of the field strength, and then the interface parameters can be determined according to the symmetrical relationship between the position of the mirror dipole and the source dipole. Both simulation analysis and laboratory test results show that the interface detection method is feasible. The related research provides new ideas for target detection in the sea.

Electronic Structures of Graphene/MoS<sub>2</sub> Heterostructure: Effects of Stacking Orientation, Element Substitution, and Interlayer Distance

Effects of stacking orientation, element substitution, and interlayer distance on electronic structures of graphene/MoS2 heterostructures were investigated using first-principles calculations. The results predicted that the stacking orientation does not take a crucial role in changing the electronic structures in contrast to element substitution, which converts the system from semiconductor to metallic. A bandgap opening originating in a Dirac band of graphene is found to be governed by the interface distance between graphene and MoS2 layers.

Enhancing fiber-matrix interface in carbon fiber/poly ether ether ketone (CF/PEEK) composites by carbon nanotube reinforcement of crystalline PEEK sizing

Crystalline poly ether ether ketone (PEEK) is an emergent effective sizing agent for carbon fiber (CF) for use in CF/PEEK composites. Soluble PEEK with the ability to recover crystallinity via simple acidification was synthesized and grafted on carbon nanotube for the first time to enhance the effectiveness and thermomechanical integrity of the based sizing, to achieve a higher level of chemical resistance and interfacial enhancement. CNT-filled, acidified-CNT-filled, and PEEK-grafted-CNT-filled sizing compounds were synthesized and coated on to CF. Proton nuclear magnetic resonance (1H NMR) and Fourier-transform infrared (FTIR) spectroscopy were used to analyze the products of chemical synthesis, whereas X-ray photoelectron spectroscopy (XPS) was used to assess the grafting reaction. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to assess the morphology of the unsized and sized CF, and a microbond test was used to evaluate the interfacial shear strength (IFSS) of the sizing. As a result, the CF/PEEK composites achieved the highest ever reported IFSS, with values of 101.4 MPa and 103.4 MPa in the acidified-CNT and PEEK-grafted-CNT samples, respectively. It is noted that the PEEK-grafted-CNT sample also exhibited greater solvent resistance due to closer interfacial distance, and an IFSS retention rate of 80%–90% in various polar and non-polar solvents. The successful application of nano-reinforcement in a CF interfacial sizing and the development of the PEEK grafting on CNT possesses an expanded application potential for CF/PEEK composites.

Diamond/c-BN van der Waals heterostructure with modulated electronic structures

The structural and electronic properties of (100), (110), and (111) diamond/cubic boron nitride (c-BN) heterostructures are systematically investigated by first principles calculation. The interface between diamond and c-BN shows the weak van der Waals interactions, which is confirmed by the interface distance and interface binding energy. The diamond/c-BN structures are the direct bandgap semiconductors with moderate bandgap values ranging from 0.647 eV to 2.948 eV. This work helps to promote the application of diamond in electronic and optoelectronic devices.

Atomic‐Scale Observation of the Local Structure and 1D Quantum Effects in vdW Stacking Mo6Te6 Nanowires

AbstractThe sub‐nanometer‐diameter transitional‐metal chalcogenides (M6X6) molecular wires are ideal 1D quantum systems. The electronic properties of such system are very sensitive to the interface interaction and local imperfection. Here, the atomic structure and local electronic structure of van der Waals (vdW) stacking Mo6Te6 nanowires fabricated by using molecular beam epitaxy are reported. Atomic‐resolution scanning tunneling microscopy measurement shows that the vdW interface distance varies from 0.71 to 1.05 nm when Mo6Te6 wires stacked on graphite, MoTe2, and Mo6Te6 surfaces. Scanning tunneling spectroscopy confirmed the 1D quantum effect of van Hove singularity and Tomonaga–Luttinger liquid behavior at 77.8 K. Single Te vacancies and their effect to the local structure distortion are observed as well. These observations shed light on the local structure and quantum effects of the M6X6 nanowire materials, which may find applications in future electronic devices.

Aromatic molecules as sustainable lubricants explored by ab initio simulations

In pursuit of sustainable lubricant materials, the in situ formation of graphitic material has been shown to effectively reduce friction at metallic interfaces. Aromatic molecules are perfect candidates for the formation of carbon-based tribofilms due to their inertness and chemical structure. We selected a group of common aromatic compounds, which are still unexplored in tribology, and we investigated their capability to reduce the adhesion of sliding iron interfaces. Ab initio molecular dynamics simulations show that hypericin, a component of St. John’s wort, can effectively separate the mating iron surfaces better than graphene. The size of this molecule, combined with the reactivity and the hindrance of its moieties, plays an important role in maintaining large interfacial distances. Stacked hypericin molecules can easily slide on top of each other due to the intermolecular repulsion arising in the presence of load. The decomposition of the lateral groups of hypericin observed in the dynamic simulations suggests that the polymerization of several molecules can occur in tribological conditions. All these results pave the way for promising alternatives to commonly employed friction modifiers.

Effects of interfacial dynamics on the damping of biocomposites

A damping model is developed based on the mechanism of interfacial interaction in nanoscale particle reinforced composites. The model includes the elasticity of the materials and the effects of interfacial adhesion hysteresis. Specific results are given for the case of bio-based PA610 polyamide reinforced by nanocrystalline cellulose (CNC), based on a previous study that showed this composite possesses very high damping. The presence of hydrogen bonding at the interface between the particle and matrix and the large interfacial area due to the filler’s nano size are shown to be the main causes of the high damping enhancement. The influence of other parameters, such as interfacial distance and stiffness of the matrix materials are also discussed. The modeling work can be used as a guide in designing composites with good damping properties.

Abstract 13198: Cardiac TRPC6 N338S is a Gain-of-Function Mutation Associated With Doxorubicin-Induced Cardiomyopathy

Introduction: Doxorubicin (DOX) is widely used for chemotherapy, but cardiotoxicity and cardiomyopathy are major adverse effects. The canonical transient receptor potential 6 gene ( TRPC6) is a putative risk gene for cardiomyopathy. Recently, a TRPC6 N338S mutation was found in a patient with DOX-induced heart failure. However, the TRPC6 N338S mutant has not been characterized, and how it affects cardiac function is unknown. Hypothesis: We hypothesized that TRPC6 N338S is a gain-of-function mutation producing intracellular Ca 2+ overload in cardiomyocytes. Methods: Using patch clamp recording, molecular biological and molecular docking analyses, we assessed the function of TRPC6 N338S heterologously expressed in HL-1 cardiac cells. Results: TRPC6 N338S significantly increased the current densities of TRPC6 (defined as 1 μM BI-749327 sensitive components, a highly selective TRPC6 inhibitor) in HL-1 cells at baseline and after exposure to 50 μM 1-oleoyl 2-acetyl-sn-glycerol (OAG, an activator of TRPC6), compared to cells expressing TRPC6 WT. Moreover, a 24-h pretreatment with 0.5 μM DOX further potentiated the OAG effects on TRPC6 WT currents with a significantly greater response in the N338S currents. Ca 2+ imaging also showed enhanced intracellular Ca 2+ levels in cells expressing the N338S mutant with OAG and DOX treatment. Biological studies found that the cytoplasmic and surface expression of TRPC6 WT and N338S mutant were identical in HL-1 cells, but those of TRPC6 N338S were markedly upregulated after treatment with 0.5 μM DOX, compared to TRPC6 WT. Molecular docking and dynamics simulation analysis unraveled that OAG binds to a pocket constituted by the pore-helix, S5 and S6 domains of TRPC6 through polar interactions. OAG binds to the same site in TRPC6 N338S with shortened interfacial distances due to additional polar and hydrogen bonding between OAG and the N338S mutant. Conclusions: TRPC6 N338S mutation strengthens the interaction with OAG, stabilizes the OAG-TRPC6 N338S complex, and enhances the OAG effects. Treatment with DOX significantly increases the expression and function of TRPC6 N338S in HL-1 cells. Hence, the TRPC6 N338S is a gain-of-function mutation and may contribute to cardiotoxicity in patients with anthracycline treatment.

Theoretical investigation on the electronic structure of TaON/WO3 heterojunction towards exploring its photocatalytic activity

A heterojunction structure of TaON/WO3 is built by stacking TaON (001) slab and WO3 (001) slab. The TaON/WO3 with the interfacial distance of 1.7 ​Å is the most stable structure. The energy band, density of states and optical absorption of the constructed crystals are calculated by the functional of B3LYP. The carrier effective mass of TaON/WO3 is less than those of TaON (001) and WO3 (001) while the values of mh∗/me∗ of TaON/WO3 are distinctly greater than those of TaON (001) and WO3 (001). Therefore, the TaON/WO3 displays significantly improved carrier mobility and separation efficiency in comparison with TaON (001) and WO3 (001). Compared to TaON (001) and WO3 (001), the TaON/WO3 demonstrates better photon capture ability. The calculation results imply that the TaON/WO3 will exhibit markedly enhanced photocatalytic activity in comparison with TaON and WO3.