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In moir\'e crystals formed by stacking van der Waals (vdW) materials, surprisingly diverse correlated electronic phases and optical properties can be realized by a subtle change in the twist angle. Here, we discover that phonon spectra are also renormalized in MoS$_2$ twisted bilayers, adding a new perspective to moir\'e physics. Over a range of small twist angles, the phonon spectra evolve rapidly due to ultra-strong coupling between different phonon modes and atomic reconstructions of the moir\'e pattern. We develop a new low-energy continuum model for phonons that overcomes the outstanding challenge of calculating properties of large moir\'e supercells and successfully captures essential experimental observations. Remarkably, simple optical spectroscopy experiments can provide information on strain and lattice distortions in moir\'e crystals with nanometer-size supercells. The newly developed theory promotes a comprehensive and unified understanding of structural, optical, and electronic properties of moir\'e superlattices., Comment: 21 pages, 4 figures

Two-dimensional transition metal dichalcogenide nanoribbons are touted as the future extreme device downscaling for advanced logic and memory devices but remain a formidable synthetic challenge. Here, we demonstrate a ledge-directed epitaxy (LDE) of dense arrays of continuous, self-aligned, monolayer and single-crystalline MoS2 nanoribbons on β-gallium (iii) oxide (β-Ga2O3) (100) substrates. LDE MoS2 nanoribbons have spatial uniformity over a long range and transport characteristics on par with those seen in exfoliated benchmarks. Prototype MoS2-nanoribbon-based field-effect transistors exhibit high on/off ratios of 108 and an averaged room temperature electron mobility of 65 cm2 V−1 s−1. The MoS2 nanoribbons can be readily transferred to arbitrary substrates while the underlying β-Ga2O3 can be reused after mechanical exfoliation. We further demonstrate LDE as a versatile epitaxy platform for the growth of p-type WSe2 nanoribbons and lateral heterostructures made of p-WSe2 and n-MoS2 nanoribbons for futuristic electronics applications. Aligned arrays of single-crystalline monolayer TMD nanoribbons with high aspect ratios, as well as their lateral heterostructures, are realized, with the growth directed by the ledges on the β-Ga2O3 substrate. This approach provides an epitaxy platform for advanced electronics applications of TMD nanoribbons.

This study evaluates the variation of the bending moment strength of the single symmetrical and double symmetrical I-beam design. This study compares the use of a double-symmetric I-section with a large, small flange, a single-symmetric I-section with a large compression and large tension flange. The study shows that the four sections have the largest wing strength with double-symmetric I-section, and the inelastic and elastic strengths are similar to those of the single-symmetric I-section, especially the elastic region is almost the same. In the plastic phase, the double symmetrical flanges have a high cross-sectional strength. In the inelastic phase, the intensity of two individual symmetrical sections of the same area is close to a double symmetrical section. The use of a single symmetrical I-beam can be preferred over a double-symmetric I-beam. This study provides a single-symmetric I-beam strength difference analysis, providing users with a variety of options for comparing cross-sections.

This paper applies the repetition index scheme (RIS) to the channel identification of cyclic prefixed (CP) multiple-input Multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems with virtual carriers (VCs) in the environment of the number of receive antennas being no less than that of transmit antennas. The VCs will cause a rank deficiency problem in computing the subspace information. With the subcarrier mapping matrix, the received signal is simplified to remove the rank deficiency. We use the RIS scheme to generate many times of equivalent symbols so the channel identification can converge with few received OFDM blocks. The RIS scheme will convert the white noise into non-white noise. With the Cholesky factorization, a noise whitening technique is developed to turn the non-white noise back to white noise. We further analyze the necessary conditions of identifiability of channel estimation. Simulations are performed to show the superiority of the proposed method.

This paper reassesses the detrimental effect on fatigue performance of welded structural steel joints due to thicker sections based on an extensive fatigue strength test database, taken from research programmes worldwide over the past half century, mostly from the offshore oil and gas and marine industries. The data entries in the database were evaluated to ensure its data integrity. Statistical analyses on these S-N data were performed with or without the thickness correction at different exposure levels to a corrosive environment, in order to re-evaluate the suitability of current standards in regard to the thickness effect. The study concentrated on T-joints, transverse butt-welded joints and tubular joints, as these are the most commonly used joint types in the offshore wind industry. The analysis indicates a general agreement of fatigue strength with the thickness effects in current standards for in-air conditions, but great conservatism for corrosive environments. In addition, the statistical models determined in this study can be used for a broader range of studies, such as probabilistic fatigue analysis.

Many mini-implantable devices have been developed and fabricated for diagnostic and treatment purposes. Wireless implantable biomicrosystems provide a desirable approach for long-term physiological signal monitoring. In this study, we implemented a wireless implantable biomicrosystem for bladder-cavity pressure measurements in a freely moving rabbit. To manage the power more effectively, a magnetic reed switch was applied to turn on/off the implantable module using a neodymium&ndash, iron&ndash, boron (NdFeB) magnet. The measured bladder pressure signal was wirelessly transmitted from the implantable module to a host unit. Our results indicated that the implantable biomicrosystem exhibited satisfactory performance and safety, as evidenced by an error percentage of less than &plusmn, 1% for pressure measurements and less than 2 &deg, C of a temperature rise under normal operation. The wireless biomicrosystem was implanted into the bladder cavity of a rabbit. Bladder pressure was simultaneously measured by both the biomicrosystem and conventional cystometry in the animal. The two signals were similar during the voiding phase, with a correlation coefficient of 0.885. Additionally, the biomicrosystem coated with polydimethylsiloxane in this study showed no cytotoxicity, which confirmed its biocompatibility. In conclusion, we demonstrated a good biocompatible wireless biomicrosystem which showed good reproducibility with respect to pressure monitoring by conventional cystometry. Further studies are needed to confirm the results of this preliminary feasibility study for actual clinical applications.

A multipollutant (Hg0/NO/dioxin)-containing gas-stream-generating system is developed to investigate the effectiveness of V2O5–WO3/TiO2 catalyst for multipollutant control. The results indicate tha...

Interlayer exciton diffusion in transition metal dichalcogenide heterostructures is controlled by the moiré potential., The properties of van der Waals heterostructures are drastically altered by a tunable moiré superlattice arising from periodically varying atomic alignment between the layers. Exciton diffusion represents an important channel of energy transport in transition metal dichalcogenides (TMDs). While early studies performed on TMD heterobilayers suggested that carriers and excitons exhibit long diffusion, a rich variety of scenarios can exist. In a moiré crystal with a large supercell and deep potential, interlayer excitons may be completely localized. As the moiré period reduces at a larger twist angle, excitons can tunnel between supercells and diffuse over a longer lifetime. The diffusion should be the longest in commensurate heterostructures where the moiré superlattice is completely absent. Here, we experimentally demonstrate the rich phenomena of interlayer exciton diffusion in WSe2/MoSe2 heterostructures by comparing several samples prepared with chemical vapor deposition and mechanical stacking with accurately controlled twist angles.

We report the layer-hybridized valley excitons in 2D hetero- and homobilayers manifested by band alignment and valley spin., Excitons in monolayer semiconductors have a large optical transition dipole for strong coupling with light. Interlayer excitons in heterobilayers feature a large electric dipole that enables strong coupling with an electric field and exciton-exciton interaction at the cost of a small optical dipole. We demonstrate the ability to create a new class of excitons in hetero- and homobilayers that combines advantages of monolayer and interlayer excitons, i.e., featuring both large optical and electric dipoles. These excitons consist of an electron confined in an individual layer, and a hole extended in both layers, where the carrier-species–dependent layer hybridization can be controlled through rotational, translational, band offset, and valley-spin degrees of freedom. We observe different species of layer-hybridized valley excitons, which can be used for realizing strongly interacting polaritonic gases and optical quantum controls of bidirectional interlayer carrier transfer.

The Amazon Picking Challenge and the Amazon Robotics Challenge have shown significant progress in object picking from a cluttered scene, yet object placement remains challenging. It is useful to have pose-aware placement based on human and machine readable pieces on an object. For example, the brandname of an object placed on a shelf should be facing the human customers. The robotic vision challenges in the object placement task: a) the semantics and geometry of the object to be placed need to be analysed jointly; b) and the occlusions among objects in a cluttered scene could make it hard for proper understanding and manipulation. To overcome these challenges, we develop a pose-aware placement approach by spotting the semantic labels (e.g., brandnames) of objects in a cluttered tote and then carrying out a sequence of actions to place the objects on a shelf or on a conveyor with desired poses. Our major contributions include 1) providing an open benchmark dataset of objects and brandnames with multi-view segmentation for training and evaluations; 2) carrying out comprehensive evaluations for our brandname-based fully convolutional network (FCN) that can predict the affordance and grasp to achieve pose-aware placement, whose success rates decrease along with clutters; 3) showing that active manipulation with two cooperative manipulators and grippers can effectively handle the occlusion of brandnames. We analyzed the success rates and discussed the failure cases to provide insights for future applications. All data and benchmarks are available at https://text-pick-n-place.github.io/TextPNP/

Steel bolt groups are often used for joining steel structures. The design strength of the steel bolt group is related to the geometric distribution, the eccentric load distance, the material strength and the load angle, thus making the analysis complicated and not easy for the user. The existing analysis methods are two kinds of elasticity and ultimate analysis. Both methods consider the stress distribution of each steel bolt and find the steel bolt at the critical position is obtained, the design load analysis is deduced. This study will consider the geometric distribution of steel bolting group affected, for a row, two rows, three rows and four rows of bolt group, considering different eccentric distance and angle of influence. Using a simple elastic analysis method to Studied the strength analysis results produced when a corner bolt is damaged due to a defect. The results show that the greater the eccentric load distance, the lower the design strength, and the load change on the vertical is more obvious than the horizontal. When the corner of the steel bolt group is removed, its design strength is likely to decrease, but at low eccentricity distance and large angles, the strength of the complete bolt is higher. This study organizes the design method of steel bolts and reviews the geometric rules of the bolt group analysis. It founded that the regular geometry needs to be reviewed in the case of large eccentric loads with small eccentricities. This study for the bolt connections strength of a certain understanding and awareness, expect the future for the safety of steel structure contribute.

Piezoelectric materials have been widely used for sensors, actuators, electronics, and energy conversion. Two-dimensional (2D) ultrathin semiconductors, such as monolayer h-BN and MoS2 with their atom-level geometry, are currently emerging as new and attractive members of the piezoelectric family. However, their piezoelectric polarization is commonly limited to the in-plane direction of odd-number ultrathin layers, largely restricting their application in integrated nanoelectromechanical systems. Recently, theoretical calculations have predicted the existence of out-of-plane and in-plane piezoelectricity in monolayer α-In2Se3. Here, we experimentally report the coexistence of out-of-plane and in-plane piezoelectricity in monolayer to bulk α-In2Se3, attributed to their noncentrosymmetry originating from the hexagonal stacking. Specifically, the corresponding d33 piezoelectric coefficient of α-In2Se3 increases from 0.34 pm/V (monolayer) to 5.6 pm/V (bulk) without any odd–even effect. In addition, we also de...

Van der Waals heterobilayers of transition metal dichalcogenides with spin–valley coupling of carriers in different layers have emerged as a new platform for exploring spin/valleytronic applications. The interlayer coupling was predicted to exhibit subtle changes with the interlayer atomic registry. Manually stacked heterobilayers, however, are incommensurate with the inevitable interlayer twist and/or lattice mismatch, where the properties associated with atomic registry are difficult to access by optical means. Here, we unveil the distinct polarization properties of valley-specific interlayer excitons using epitaxially grown, commensurate WSe2/MoSe2 heterobilayers with well-defined (AA and AB) atomic registry. We observe circularly polarized photoluminescence from interlayer excitons, but with a helicity opposite to the optical excitation. The negative circular polarization arises from the quantum interference imposed by interlayer atomic registry, giving rise to distinct polarization selection rules for interlayer excitons. Using selective excitation schemes, we demonstrate the optical addressability for interlayer excitons with different valley configurations and polarization helicities. The interlayer coupling in van der Waals heterostructures is sensitive to the interlayer atomic registry. Here, the authors investigate the polarisation properties of epitaxially grown, commensurate WSe2/MoSe2 heterobilayers with well-defined atomic registry, and observe negative, circularly polarized photoluminescence from interlayer excitons.

Since the domestic power plants are typically operated at a partial load rather than the design point, the thermal expansion decreases, resulting in misalignment between first stage rotor and second stage stator. In this study, we investigate the heat transfer characteristics of a misalignment under purge flow at the second stage vane endwall through heat/mass transfer experiments using the naphthalene sublimation method and CFD simulations. Experiments are conducted at 4 vanes in a linear cascade with an inlet Reynolds number of 120,000, based on the vane axial chord length. In the absence of purge flow, a high heat transfer occurs in upstream of the vane endwall via horseshoe vortices. When a misalignment occurs, a more severe thermal load is observed as the mainstream attaches to the endwall due to recirculation flow upstream of the leading edge. Additionally, two high heat transfer regions are observed when a step-induced vortex occurs in the vane flow path. In case of the purge flow, the mixing of the mainstream and purge flow increases the intensity of the vortex, which increases heat transfer in the region upstream of the both flat and stepped endwall. In conclusion, we have found that the step difference has a crucial effect on thermal damage upstream of the second stage vane endwall as a little misalignment occurrence. The area-averaged heat transfer of the stepped endwall is increased by about 11.4% and 13.7% without and with purge flow, respectively, as compared to that of the flat endwall.

The American Institute of Steel Construction (AISC) provides conservative elastic and more realistic instantaneous center of rotation (IC) methods to analyze eccentrically loaded weld groups in plane. The current AISC design manual provides tables for coefficient C, which are used to obtain the design strength of weld group patterns, at only six inclined angles (θ = 0°, 15°, 30°, 45°, 60°, and 75°). For other angles, either a direct analysis must be performed or using the values for the next lower angle increment in the tables is recommended in the manual except for straight-line interpolation. This work develops an iterative algorithm to implement a direct analysis, and proposes a rational interpolation method between C values for loads at various angles not tabulated in manual tables without the tediousness of the IC method. The proposed method is easy to implement but reasonably accurate instead of using the C values for the next lower angle increment in the tables or direct analysis. This work...

Many floating offshore wind turbine (FOWT) concepts are light displacement platforms moored in shallow water and exposed to significant storms with high winds. Shock loads (also called snap loads) on the mooring lines can occur when an FOWT experiences large wave- and wind-induced motions. A typical snap event is characterized by a temporary slackness in the line followed by a sharp spike in tension whose magnitude can considerably exceed typical values of local tension maxima. In this study, we investigate seven experimental tests of a moored FOWT under survival storm conditions (i.e., a 100-year storm). For all these cases, the significant wave height and peak wave period are held constant at 10.5 m and 14.3 s respectively, while the wind speed is varied from 0 to 30.5 m/s. The wind conditions range from a steady wind to turbulent wind characterized by a chosen spectrum. Several snap events are found to result in the windward mooring line. The duration of these events range from 7.5 to 10.5 s, and the maximum tension values recorded are 37–68% higher than the corresponding cyclic non-snap tension maxima. The dynamic tension in the measured time histories are separated into snap-induced events and those that are not associated with a snap event based on criteria specified in marine operation practices; probability distributions of these separate events are analyzed. The exceedance probability curve of the dynamic tension in the higher ranges contributed to by snap-induced tension shows different characteristics compared to the lower tension range values that are related to the cyclic dynamic tension. There appears to be a clear demarcation point for this change in the probability curve characteristics. We propose a composite Weibull probability distribution for the mooring line dynamic tension that incorporates the effects of snap events. The model is composed of two Weibull distributions with different characteristics on either side of a transition tension value, and whose parameters are estimated from test data. The transition tension is related to the maximum cyclic dynamic tension in an extreme storm event, as specified by recommended practices. The proposed distribution model provides a good fit to the measured tension data, particularly in the extreme range. A design extreme value is developed for systems where snap loads are generally non-existent or are associated with very low probabilities of occurrence. When the shock load incidence probability is higher, the developed composite Weibull distribution model could offer a good starting point for the prediction of extreme dynamic tensions of a FOWT mooring system.

The condition monitoring and fault diagnosis is an important function of the intelligent mechanics. Understanding equipment’s condition helps engineers avoiding inevitable catastrophe that could cause unplanned downtime and affect the system reliability and safety. In addition, alleviation of the machine’s incipient faults helps the machine running efficiently and reduces energy consumption. This paper presents field case studies of industrial induction motors including pumps and fans from several facility factories, and uses electrical data not only to analyze machine’s condition and but also to detect the faults. Current spectrum analysis is mainly employed to detect the anomaly. In addition, we propose a ratio of current divided by voltage (C/V) spectrum to represent the steady gain property of the system. This ratio is expected to mitigate the effect of Variable-frequency drive’s noise and disturbance on current spectrum and to reduce the false alarm caused by Variable-frequency drive (VFD). The combination of current spectrum and spectrum ratio is beneficial in the conditional analysis of industrial motors.

The aim of this paper is to establish a simple approach to experimentally study the mooring line damping in shallow water, where snap loading may occur more frequently. Experimental measurements were conducted in a wave basin at a scale of 1:50, which corresponds to a full scale of 28 m water depth. A chain made by stainless steel was used, and the tension force at the fairlead was measured by tension gages. Moreover, the line geometry, touchdown point speed, and mooring line velocity were derived from image processing techniques. Surge motions at fairlead were driven from a programmable wavemaker. Regular surge motions with different frequencies and pretensions were tested in this system in order to investigate the quasi-static and dynamic behaviors of the mooring chain. In the quasi-static test, the mooring line keeps a typical catenary shape, and its indicator diagram exhibits a smooth-closed curve. In the dynamic test, the mooring line is fully lifted from the seabed, and it cyclically goes through the stage of semitaut and fully taut. We successfully reproduced a snap event in the laboratory scale, and the resulting mooring line damping can considerably increase in this manner. Two criteria for snap event were examined, and both of them were verified by the experiments.

This study experimentally investigated the influence of heterogeneous wettability-patterned surfaces with varying inter-spacing on flow boiling heat transfer characteristics. The test surfaces consisted of three fluorooctyltrichlorosilane hydrophobic-patterned array structures having a triangle, inverted triangle, and circular shape on a SiO2- hydrophilic substrate, with an inter-spacing of 0.75 or 1 mm. The working fluid was deionized water, and the Reynolds number was 6,000 at atmospheric pressure. Among the test surfaces, varying the inter-spacing between neighboring hydrophobic patterns slightly enhanced the heat transfer coefficient (HTC) due to changing the bubble characteristics. In terms of the shape effect of hydrophobic patterns, the heterogeneous wettability-patterned surfaces dominated the overall flow boiling heat transfer performance showing a significant increase in critical heat flux (CHF) compared to the Si surface, by 40–43%. In addition, all of the wettability test surfaces showed a markedly higher heat transfer coefficient than the Si surface, by 35–163%. This experiment is explained by analyzing the relationship between bubble lift forces and the various hydrophobic-patterned shapes in a horizontal flow channel, in an attempt to better understand flow boiling heat transfer and optimize the pattern design.

Ag/TiO2 composite films with the different Ag contents of 1, 3, and 5 vol.% were deposited at 25, 200, and 400 °C on glass substrates by radio frequency sputtering with a single cermet target formed by hot pressing the Ag nanoparticle-decorated TiO2 nanopowder at 900 °C in argon atmosphere for 30 min, followed by annealing in air and the reduction under vacuum heating or by NaBH4. All the TiO2 films were analyzed by X-ray diffraction technique to have an amorphous structure. High deposition and annealing temperatures all led to Ag aggregation in Ag/TiO2. Photodegradation of acid black 1 dye was used as the screen test to evaluate the photocatalytic ability of Ag/TiO2 films, before the antibacterial test was preceded. The antibacterial ability on Escherichia coli was also evaluated. The 25 °C-deposited 3% Ag/TiO2 films of 80 nm in thickness had the best performance in optical transmittance above 70% and killing the E. coli. The mechanism for the fluorescent lamp-induced bactericide of the 3% Ag/TiO2 film is proposed. The amorphous 3% Ag/TiO2 film had larger band gap of 3.67 eV than the annealed ones and is expected not to be excited by the fluorescent lamp, but to prolong the lifetime of the thermally induced, not photo-induced, charge carriers in the Ag/TiO2 by its electric field of the illumination light and the attraction by Ag nanoparticles

This study proposed a novel configuration of active LED graphite-composite heat sink and experimentally investigated the effects of vent channels and metal conductive base on the fluid flow and heat transfer characteristics of this active heat sink. The heat sink was made of the graphite powders, aluminum-alloy powders, and adhesive mixed in specific proportion by the vacuum-pressure injection technique. The cost and weight of this graphite-composite material are much lower than those of aluminum alloy. The configuration of heat sink is a hollow circular cylinder with multiple radial fins. Different motor fans can be put in the chamber of heat sink, with various vent-channel positions and orientations (vertical vent channels, horizontal upper-row vent channels, and horizontal bottom-row vent channels) and numbers of channels (24, 36, 48, and 72) in the heat sink to enhance overall cooling performance by driving through airflow. The results indicate that the overall Nusselt number (Nu) of the graphite-composite heat sink with motor fan was 2.23–2.50 times that without motor fan. The numbers of vent channels in heat sink were positively related to the total flow rate of through air. Thus, the heat sink with the most vent channels had the maximum Nu in the motor-fan mode. When an additional annular aluminum-alloy conductive base was mounted in the graphite-composite heat sink with the most vent-channel configuration, the Nu was 35% higher than that without conductive base in motor-fan mode, proving the metal conductive base was effective. The optimal vent-channel configuration in this study was also used for the full aluminum-alloy heat sink, the corresponding Nu of the models without/with motor fan were compared with the full aluminum-alloy heat sink without vent channel, the heat transfer enhancements were about 13% and 127%, respectively.

Emerging issues in boiling heat transfer include enhancing heat transfer uniformity/stability, and critical heat flux (CHF). Microcavity structures improve heat transfer uniformity/stability by departing bubbles with arranged formation due to pinning effects and regular pitch. Ultrasonic actuation induces an acoustic field on departed bubbles, and this enhances contact line instability between the bubble and microcavity structures, resulting in an increased dissipation rate of smaller bubbles. In this study, we demonstrate that synergetic effects from microcavity structures and ultrasonic actuation can enhance CHF and thermal stability while also improving temporal/spatial temperature uniformity. Applying microcavity structures with ultrasonic actuation, we observe smaller and faster bubbles' departure with the proposed formation. These bubble departure characteristics on the microcavity surface with ultrasonic actuation enhance CHF and thermal stability by delaying bubble coalescence and ensuring liquid paths between smaller and faster-departed bubbles. Thus, when ultrasonic actuation is applied to the microcavity structure, CHF increased by 20%, and temporal/spatial temperature variations near CHF were reduced to less than 1/2 and 1/3, respectively, compared to no actuation case. This research will help to understand the interaction of ultrasonic wave and bubbles, and to show the way to overcome CHF limitations of passive methods using microsized structures.

Monolayer transition metal dichalcogenides, such as MoS2 and WSe2, have been known as direct gap semiconductors and emerged as new optically active materials for novel device applications. Here we reexamine their direct gap properties by investigating the strain effects on the photoluminescence of monolayer MoS2 and WSe2. Instead of applying stress, we investigate the strain effects by imaging the direct exciton populations in monolayer WSe2–MoS2 and MoSe2–WSe2 lateral heterojunctions with inherent strain inhomogeneity. We find that unstrained monolayer WSe2 is actually an indirect gap material, as manifested in the observed photoluminescence intensity–energy correlation, from which the difference between the direct and indirect optical gaps can be extracted by analyzing the exciton thermal populations. Our findings combined with the estimated exciton binding energy further indicate that monolayer WSe2 exhibits an indirect quasiparticle gap, which has to be reconsidered in further studies for its fundamental properties and device applications., Monolayer transition metal dichalcogenides have so far been thought to be direct bandgap semiconductors. Here, the authors revisit this assumption and find that unstrained monolayer WSe2 is an indirect-gap material, as evidenced by the observed photoluminescence intensity-energy correlation.

It is critically important to characterize the band alignment in semiconductor heterojunctions (HJs) because it controls the electronic and optical properties. However, the well-known Anderson's model usually fails to predict the band alignment in bulk HJ systems due to the presence of charge transfer at the interfacial bonding. Atomically thin 2D transition metal dichalcogenide materials have attracted much attention recently since the ultrathin HJs and devices can be easily built and they are promising for future electronics. The vertical HJs based on 2D materials can be constructed via van der Waals stacking regardless of the lattice mismatch between two materials. Despite the defect-free characteristics of the junction interface, experimental evidence is still lacking on whether the simple Anderson rule can predict the band alignment of HJs. Here, the validity of Anderson's model is verified for the 2D heterojunction systems and the success of Anderson's model is attributed to the absence of dangling bonds (i.e., interface dipoles) at the van der Waal interface. The results from the work set a foundation allowing the use of powerful Anderson's rule to determine the band alignments of 2D HJs, which is beneficial to future electronic, photonic, and optoelectronic devices.