Physical vapor deposited (PVD) molybdenum disulfide (nominal composition MoS2) is employed as a thin film solid lubricant for extreme environments where liquid lubricants are not viable. The tribological properties of MoS2 are highly dependent on morphological attributes such as film thickness, orientation, crystallinity, film density, and stoichiometry. These structural characteristics are controlled by tuning the PVD process parameters, yet undesirable alterations in the structure often occur due to process variations between deposition runs. Nondestructive film diagnostics can enable improved yield and serve as a means of tuning a deposition process, thus enabling quality control and materials exploration. Grazing incidence X-ray diffraction (GIXRD) for MoS2 film characterization provides valuable information about film density and grain orientation (texture). However, the determination of film stoichiometry can only be indirectly inferred via GIXRD. The combination of density and microstructure via GIXRD with chemical composition via grazing incidence X-ray fluorescence (GIXRF) enables the isolation and decoupling of film density, composition, and microstructure and their ultimate impact on film layer thickness, thereby improving coating thickness predictions via X-ray fluorescence. We have augmented an existing GIXRD instrument with an additional X-ray detector for the simultaneous measurement of energy-dispersive X-ray fluorescence spectra during the GIXRD analysis. This combined GIXRD/GIXRF analysis has proven synergetic for correlating chemical composition to the structural aspects of MoS2 films provided by GIXRD. We present the usefulness of the combined diagnostic technique via exemplar MoS2 film samples and provide a discussion regarding data extraction techniques of grazing angle series measurements.

As the measurement scale shrinks, the reliability of nanoscale measurement is even more crucial for a variety of applications, including semiconductor electronics, optical metamaterials, and sensors. Specifically, it is difficult to measure the nanoscale morphology at the exact location though it is required for novel applications based on hybrid nanostructures combined with 2D materials. Here, we introduce an advanced hybrid positioning system to measure the region of interest with enhanced speed and high precision. A 5-axis positioning stage (XYZ, R, gripper) makes it possible to align the sample within a 10-μm field of view (FOV) in both the scanning electron microscope (SEM) and the atomic force microscope (AFM). The reproducibility of the sample position was investigated by comparing marker patterns and denting points between the SEM and AFM, revealing an accuracy of 6.5 ± 2.1 μm for the x-axis and 4.5 ± 1.7 μm for the y-axis after 12 repetitions. By applying a different measurement process according to the characteristics of 2D materials, various information such as height, length, or roughness about MoTe2 rods and MoS2 film was obtained in the same measurement area. As a consequence, overlaid two images can be obtained for detailed information about 2D materials.

Here, a well crystalline 3D flower-like structured MoS2 (~420 nm) has been successfully synthesized on a large scale by a simple hydrothermal technique. The evolution of morphology in the formation process has also been investigated. The crystallinity, purity, and morphology of the sample are characterized by powder X-ray diffraction, Fourier-transform infrared spectroscopy, fieldemission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) techniques. The FESEM and TEM images reveal that the sample exhibits a uniform 3D flower-like microsphere shape with folded nanosheets, which are stretched out along the edge of the microsphere. The electrochemical performance of the sample has been investigated by cyclic voltammogram, galvanostatic charge–discharge, and electrochemical impedance spectroscopy studies. The results of the electrochemical analysis suggest that the material delivers a maximum specific capacitance (Csp) of 350 F/g at a discharge current density of 0.25 A/g with energy density 17.5 Wh/kg. It also exhibits good capability and excellent cyclic stability (94% capacity retention after 1,000 cycles in 1 A/g) owing to the coupling effect of electrical conductivity with the interesting morphology and larger active surface area. Hence, the sample may be used as a promising electrode material for high-performance energy storage devices.

Layered transition metal dichalcogenides (TMDs) have attracted interest due to their promise for future electronic and optoelectronic technologies. As one approaches the two-dimensional (2D) limit, thickness and local topology can greatly influence the macroscopic properties of a material. To understand the unique behavior of TMDs it is therefore important to identify the number of atomic layers and their stacking in a sample. The goal of this work is to extract the thickness and stacking sequence of TMDs directly by matching experimentally recorded high-angle annular dark-field scanning transmission electron microscope images and convergent-beam electron diffraction (CBED) patterns to quantum mechanical, multislice scattering simulations. Advantageously, CBED approaches do not require a resolved lattice in real space and are capable of neglecting the thickness contribution of amorphous surface layers. Here we demonstrate the crystal thickness can be determined from CBED in exfoliated 1T-TaS2 and 2H-MoS2 to within a single layer for ultrathin ≲9 layers and ±1 atomic layer (or better) in thicker specimens while also revealing information about stacking order—even when the crystal structure is unresolved in real space.

Here we report on the photocurrent response of two-dimensional (2D) heterostructures of sputtered MoS2 on boron nitride (BN) deposited on (001)-oriented Si substrates. The steady state photocurrent (I ph) measurements used a continuous laser of λ = 658 nm (E = 1.88 eV) over a broad range of laser intensities, P (∼1 μW < P < 10 μW), and indicate that I ph obtained from MoS2 layers with the 80 nm BN under layer was ∼4 times higher than that obtained from MoS2 layers with the 30 nm BN under layer. We also found super linear dependence of I ph on P (I ph ∝ P γ, with γ > 1) in both the samples. The responsivities obtained over the range of laser intensity studied were in the order of mA/W (∼12 and ∼2.7 mA/W with 80 nm BN and 30 nm BN under layers, respectively). These investigations provide crucial insight into the optical activity of MoS2 on BN, which could be useful for developing a variety of optoelectronic applications with MoS2 or other 2D transition metal dichalcogenide heterostructures.

This article features the importance of nanomaterial–protein interfaces, with a special interest on two-dimensional (2D) nanomaterials, for next generation sensors and electronics. Graphene, the first isolated and studied 2D nanomaterial, is taken as the material of most interest and then focused on its engineering by heteroatom doping. The success of graphene engineering for sensors widened the search for better and efficient biosensor platforms of other layered materials such as boron nitride and transition metal dichalcogenides. But functionalization of 2D backbones with biomolecules often ends up with the disruption of the biological activities due to various reasons. This has to be fundamentally studied and corrected for the clinical implementation of these materials based novel sensing platforms in point-of-care devices and micro-fluidic chips. At the end, importance of various 2D materials–biomolecule interfaces is discussed, and MoS2 based label-free biosensor is highlighted. A method for the modification of MoS2–biomolecule interaction via covalent functionalization of oxygen functionalities in MoS2 is also proposed.

In the past 20 years, one of the best catalytic materials for hydrodesulphurization reactions of crude oil has been the transition sulfides, MoS2, known also as the “workhorse” of the refinery industry. It has been proven by this and other research groups that the MoS2 laminar structure can increase its catalytic activity when promoted with cobalt or nickel. The location of active sites seem to be at rim and edge sites on that particular laminar structure, as demonstrated using Mössbauer spectroscopy and x-ray techniques. However, due to maximum capability of this promoted systems, Co(Ni)/MoS2 to remove heterogeneous atoms (S, N, O) - a search for new catalytic materials has currently been an ongoing activity in the HDS community. Here, we will present the new family of ternary phase catalyst with special emphasis on their structural aspects, as revealed by aberration corrected (Cs) high-resolution transmission electron microscopy techniques, in an attempt to describe the nature of active sites on this porous nano-rod like catalytic materials.

Thermoplastic based composites containing different weight fractions of molybdenumdisulfide (MoS2) solid lubricant were developed by injection molding.Polymethyl methacrylate (PMMA) and polycarbonate (PC) were chosen for the thermoplasticmatrices. In order to characterize the interfacial adhesion between the matrices and thefiller, we observed the fracture morphologies of selected composites. Micrographs of thefractured surfaces showed removal of MoS2 particles by microcraking as well asthe presence of voids in the case of PMMA/MoS2 composites. These observationswere confirmed by complementary images obtained using the X-ray tomography. The additionof an appropriate coupling agent may improve the adhesion between the MoS2particles and the polymer matrix. Tribological behavior of the composites was alsoinvestigated using a ball-on-flat microtribometer with a high chromium steel ballantagonist. It was found that the addition of MoS2 particles didn’t improve thetribological performance of the composite in the case of PMMA matrix unlike the case of PCmatrix where the friction coefficient was considerably reduced.

Understanding the morphology of catalytically active materials has been approached successfully in past decades using field electron microscopy in scanning and transmission modes. In this respect, some simulated TEM measurements for unsupported promoted molybdenum di-sulfide (MoS2/Co) provided some insights about molecular structure in those catalytic layered transition metal sulfides (LTMS). However, due to poor resolution, lack of color enhancement, and other factors, sections of those materials observed under TEM do not resolve the structure by itself; in particular about the localization of cobalt atoms for promoted MoS2 unsupported catalyst. This work concludes an epitaxial growth of MoS2 slabs over (111)-Co9S8 crystallographic plane, with a stacking degree size of 6 slabs. Results presented in here are obtained using experimental HRTEM and TEM simulations using the multi-slice method with a slice thickness of 25 Å and projected potential, where ai and bi are coefficients to be determined.