A rational scheme for the determination of the resolving power of a scanning electron microscope (SEM) has been a long-standing unresolved scientific issue. The objective measurement of the image resolution according to the ISO terminology definition is always difficult, and different measurement methods used in practice now are all inconsistent with the ISO terminology definition and do not follow the Rayleigh criterion. Here, we establish a sharpness-resolution conversion curve method based on physical modeling of SEM imaging with the help of Monte Carlo simulation. The simulated secondary electron images of the resolution sample enable the build-up of the conversion curve via the simultaneous evaluation of image sharpness and image resolution under both the Rayleigh criterion and the Rose criterion. The obtained conversion curves for realistic 3D structures of resolution samples show nonlinearity and provide a convenient means by programmed measurement routine, establishing a scientifically sound way and robust framework for automatic evaluation of SEM instruments based on their resolving performance.

We report calculations of charging effect on an isolated conductor, gold nanosphere, under electron beam bombardment at primary electron energies of 0.1–10 keV based on an up-to-date Monte Carlo simulation method. The calculations consider electron flow in sample, in which the electron yield is almost equivalent to the case when the electron flow is not considered. The electron yields and charging spatial distribution are obtained. For comparison, the calculation for bulk conductor is also performed, for which the time average of electric potential is found to reproduce the law of electrostatics.

Compared to single two-dimensional (2D) materials, stacking layered 2D materials with van der Waals (vdW) heterostructures offers novel opportunities to achieve desired exotic properties. Herein, 2D Sb/SnSe vdW heterostructure is constructed by vertically stacking the antimonene (Sb) monolayer on the tin selenide (SnSe) monolayer. We have conducted a theoretical study by using the first-principles calculations to comprehensively examine the electronic, optical, and mechanical properties. Phonon dispersion and ab initio molecular dynamics simulations have demonstrated that the Sb/SnSe vdW heterostructure possesses remarkable stability, ensuring its robustness up to 900 K. The Sb/SnSe vdW heterostructure is characterized as a semiconducting material with a direct band gap of 0.24 eV, calculated by the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional method. Compared to the pristine Sb and SnSe monolayers, the Sb/SnSe vdW heterostructure exhibits a lower work function value of 3.82 eV. Furthermore, the carrier mobility of the heterostructure demonstrates anisotropic characteristics with a notable improvement in hole-mobility (12.05 x 103 cm2V- 1s- 1) along the y-direction. The Sb/SnSe vdW heterostructure shows enhanced broadband absorption spectra, especially in the visible to nearinfrared ranges. Our findings underscore the potential of the Sb/SnSe vdW heterostructure for future nanoelectronic and optoelectronic technologies.

The multislice method is an important algorithm for electron diffraction and image simulations in transmission electron microscopy (TEM). We have proposed a quantum algorithm of the multislice method based on quantum circuit model previously. In this work, we have developed an improved quantum algorithm. We reconstruct the phase-shifting quantum circuit without using the multi-controlled quantum gates, thereby significantly improve the computation efficiency. The improved quantum circuit also allows further gate count reduction at the cost of a controllable error. We have simulated the quantum circuit on a classical supercomputer and analyzed the result to prove the feasibility and correctness of the improved quantum algorithm. We also provide proper parameter settings through testing, allowing the minimization of the necessary number of quantum gates while limiting the relative error within 1%. This work demonstrates the potential of applying quantum computing to electron diffraction simulations and achieving quantum advantages.

Though extensive experiments have been performed in the past to measure electron emission properties under electron beam bombardment, reliable measured data for clean and smooth surfaces are still lacking for most elemental solids. In this study, we have conducted a comprehensive Monte Carlo simulation to examine electron emission yields, including secondary electron yield (SEY), backscattering coefficient (BSC), and total electron yield (TEY), for germanium. The uncertainties associated with theoretical calculations have also been assessed with a total of 4608 scattering models by considering several dominant factors that can influence the calculated yields, i.e., optical energy loss function dataset, work function data, dielectric function model for electron inelastic scattering, and scattering potential for electron elastic scattering. Our results indicate that the work function value significantly affects the simulated SEY, and the energy loss function dataset and elastic scattering potential moderately influence both SEY and BSC. Our simulated BSC data are somewhat higher than most of the experimental measurements, while the simulated SEY data are mostly lower than the experimental data within the estimated theoretical uncertainty. This study highlights the critical need for establishing an accurate database of electron emission yields using theoretical modeling, considering particularly the unreliability of the previous experimental data caused by surface contamination during measurements.

Two-dimensional (2D) ternary transition metal chalcogenides (TMCs) are promising for thermoelectric (TE) applications because of their low structural symmetry, high in-plane anisotropy, and adjustable band gap. A high-performance TE material requires high electrical conductivity, a large power factor PF, and a sizable dimensionless figure of merit ZT. This study focuses on the TE properties, including electrical and phonon transport properties, of highly in-plane anisotropic 2D-ZrGeTe4 based on combined first-principles and semiclassical Boltzmann theory. First, our results prove that 2D-ZrGeTe4 is mechanically, dynamically, and thermodynamically stable as a free-standing monolayer, which can be attributed to the van der Waals nature of ZrGeTe4. Next, we show that ZrGeTe4 exhibits a tunable band gap, exhibiting an indirect-to-direct band gap transition from the 3D bulk to the 2D monolayer. The electron and hole mobilities are highly anisotropic and dominate in the x-direction. Furthermore, 2D-ZrGeTe4 exhibits a large PF and low lattice thermal conductivity, yielding a high theoretical ZT of 6 and 3 for n-type and p-type at 900 K, respectively. Owing to its rich anisotropy, band degeneracy capabilities, and extreme phonon anharmonicity, 2D-ZrGeTe4 could emerge as a promising candidate for advanced TE applications at high-temperature ranges.

This study presents a novel method for extracting inelastic mean free paths (IMFPs) of electrons in solids from the backscattered electron spectrum (BES) using iterative Monte Carlo simulations. In our approach, the IMFP is parameterized using the Tanuma–Powell–Penn (TPP-2M) formula and a classical trajectory Monte Carlo simulation is used to model electron transport processes and generate a theoretical BES. Through an iterative process, we optimize the TPP parameters to achieve the best fit between the simulated and experimental spectra over a wide energy range. This method was applied to determine the IMFPs of 25 targets, such as C (graphite), Mg, Al (100), Al (111), Si, Ti, V, Cr, Fe, Co, Ni, Cu (100), Cu (110), Cu (111), Mo, Ru, Rh, Ag, Sn, W, Re, Ir, Pt, Au, and Bi, in the energy range from 200 to 4900 eV, using a comprehensive experimental BES data set. The results demonstrate that the IMFPs obtained with our BES method show an average root-mean-square deviation of approximately 15% from values calculated using the full-Penn algorithm and the standard TPP-2M formula. This approach not only provides a new technique for the IMFP measurement but also offers a novel perspective for utilizing the continuous background signal in surface electron spectroscopy, which is typically overlooked.

The frequency-dependent energy loss function and the related optical constants [refractive index n(omega) and extinction coefficient k(omega)] and dielectric functions [epsilon 1(omega) and epsilon 2(omega)] for three rare earth metals, i.e., terbium (Tb), gadolinium (Gd), and samarium (Sm), were derived in a wide range of energy loss up to around 200 eV from reflection electron energy loss spectroscopy (REELS) spectra. The latest reverse Monte Carlo analysis method was employed to subtract ELFs from REELS spectra, based on physical modeling of the electron transport in the surface region of a sample. The high accuracy of the subtracted ELFs was verified by applying the Thomas-Ritchie-Kuhn and the perfect-screening sum rules.

We incorporate experimental reflection electron energy loss spectroscopy (REELS) spectrum data with theoretical analysis to precisely determine the energy loss function (ELF) of tungsten (W) in the energy loss range of 0.1–110 eV at the incident electron energies of 1 keV, 2 keV and 3 keV. Employing the reverse Monte Carlo (RMC) method, we have obtained an averaged ELF whose relative errors of the perfect-screening sum rule and oscillator-strength sum rule were ∼ 0.70 % and 0.68 %, respectively. This ELF was then used to derive the optical constants and complex dielectric function. Furthermore, we have successfully differentiated between bulk and surface contributions to the REELS spectra throughout the entire considered energy loss range.

A model-based library (MBL) method has already been established for the accurate measurement of the critical dimension (CD) of semiconductor linewidth using critical dimension scanning electron microscope (CD-SEM) images. In this work, the MBL method is further investigated by combining CD-SEM image simulation and a neural network algorithm. The secondary electron linescan profiles were first calculated using a Monte Carlo simulation method, enabling us to obtain the dependence of linescan profiles on the selected values of various geometrical parameters (e.g. top CD, sidewall angle and height) for Si and Au trapezoidal line structures. Machine learning methods have then been applied to predict the linescan profiles from a randomly selected training set of the calculated profiles. The predicted results agree very well with the calculated profiles with the standard deviations of 0.1% and 6% for the relative error distributions of Si and Au line structures, respectively. The findings show that the machine learning methods can be practically applied to the MBL method for reducing the library size, accelerating the construction of the MBL database and enriching the content of the available MBL database.

The energy loss functions (ELFs) of Fe and Ni have been derived from measured reflection electron energy loss spectroscopy (REELS) spectra by a reverse Monte Carlo analysis in our previous work. In this work, we present further improvements of ELFs for these metals. For Fe, we have updated ELFs at primary electron energies of 2 keV and 3 keV in a wider photon energy region (0–180 eV) with a better accuracy, which is verified by sum rules. Regarding to Ni, we supplement the ELF at primary energy of 5 keV and we also improve the data accuracy at 3 keV. Applying these new and more accurate ELFs we present the optical constants and dielectric functions for the two metals. The improvements were highlighted by comparing our present results with the previous data.

The energy loss function (ELF) of the narrow bandgap semiconductor, InSb, was derived from the reflection electron energy loss spectroscopy (REELS) spectrum measured at 4 keV incident electron energy in an energy loss range of 1.6-200 eV using a high energy resolution electron spectrometer. The experimental spectrum was analyzed with the reverse Monte Carlo (RMC) method, which integrates the classical trajectory Monte Carlo simulation with the simulated annealing method for optimizing the trial ELF. Subsequently, the complex dielectric function epsilon(omega), refractive index and extinction coefficient were determined from the obtained ELF in the energy loss (i.e. photon energy) range of 1.6-200 eV. The validity of the obtained data was verified by the f-sum rule, ps-sum rule, inertial sum rule and dc-conductivity sum rule. We found that our calculated data of InSb fulfill the sum rules with very high accuracy; therefore, the use of these calculated optical data in material science and surface analysis is highly recommended for further applications.

We have calculated electron backscattering coefficients, η(Ep), at primary electron energies Ep of 0.1–100 keV for three elemental and intermediate atomic number solids, Cr, Co and Pd, with an up-to-date Monte Carlo simulation model. A relativistic dielectric functional approach is adopted for the calculation of the electron inelastic cross section, where several different datasets of optical energy loss function (ELF) are adopted. The calculated backscattering coefficient is found to be substantially affected by the ELF, where the influence can be seen to follow the f- and ps-sum rules and the resultant energy dependence of electron inelastic mean free path. To understand the uncertainties involved in a comparison with experimental data both the theoretical uncertainty due to the elastic cross-section model and the experimental systematic error for the contaminated surfaces are investigated. A total of 192 different scattering potentials are employed for the calculation of Mott's electron elastic cross section and this theoretical uncertainty is confirmed to be small. On the other hand, the simulation of contaminated Co and Pd surfaces with several carbonaceous atomic layers can well explain the experimental data. The present results indicate that accurate backscattering coefficient data should be either measured from fully cleaned surfaces or obtained from modern Monte Carlo theoretical calculations involving reliable optical constants data. With the recent progress in the accurate measurement of optical constants by reflection electron energy loss spectroscopy technique, constructing a reliable theoretical database of electron backscattering coefficients for clean surfaces of elemental solids is highly hopeful.

First-principles calculations were employed to study the molecular and dissociative adsorption of CO2, H2O, O2 and N2 on a LaB6(100) surface. The adsorption energy calculation results indicate that these gas molecules can form thermodynamically stable adsorption structures. Dissociative adsorption is always accompanied by more electron transfer compared to molecular adsorption, which is one of the necessary conditions for dissociation to occur. Bader charge analysis indicates that the adsorption of gas molecules on the LaB6(100) surface is always accompanied by electron transfer from the surface to the adsorbed molecules. This electron transfer forms a dipole moment from the adsorbed molecule towards the surface, leading to an increase in the work function of LaB6(100). This mechanism is a crucial aspect of the LaB6(100) poisoning effect. Additionally, LaB6(100) sometimes exhibits a certain degree of resistance to poisoning. In such cases, after the adsorption of gas molecules, local regions of the LaB6(100) surface become negatively charged, which counteracts the poisoning effect to some extent. Using electronic density of states and electron localization function analyses, we examined the nature of the chemical bonds. It was found that La tends to form non-covalent bonds with the adsorbates, whereas B tends to form covalent bonds with them. The 2p orbitals of B play a significant role in the formation of these covalent bonds in most cases.

Black phosphorene (BlackP), like alpha-SiS, is a two-dimensional semiconducting material for advanced microelectronics, with a moderate band gap. Even yet, the epitaxial growth of alpha-SiS on a fertile substrate has proven to be a formidable obstacle, delaying its widespread production for technological applications. Here based on first-principles approaches we identify that alpha-SiS (which is not a layered material in bulk form) monolayer could be stabilized either in freestanding form or supported on few layers of a BlackP substrate owing to its isovalency nature and the inherent structural resemblance between the two. Our calculation results demonstrate that alpha-SiS monolayer is stable on BlackP. Furthermore, the synergistic interfacial effect makes BlackP-like alpha-SiS and BlackP (alpha-SiS/BlackP) van der Waals (vdW) heterostructure a viable contender for power-driving sodium-ion batteries owing to relatively high binding strength, ultrafast diffusivity (0.08 eV in region-III), transition from semiconducting to upon sodiation, and substantially high theoretical capacity (329 mAhg(-1)). Moreover, the alpha-SiS/BlackP vdW heterostructure possesses high optical absorption strength similar to 10(5) cm(-1), and can effectively harvest visible solar radiation. The alpha-SiS growth on such semiconducting substrates could become a novel platform for next-generation nano-energy technology.

To achieve high-precision nanometrology, a self-traceable grating reference material has been reported and prepared using atom lithography and soft x-ray interference techniques (Liu et al 2021 Nanotechnology 32 175 301). In this work, we employ a Monte Carlo simulation method to investigate the scanning electron microscopy (SEM) image contrast and linewidth characterization of the grating linewidth. The 3D structure of mushroom-shaped grating lines made of multilayers (Pt, SiO2 and Si) is modeled according to transmission electron microscopy (TEM) images, enabling the SEM linescan profiles of secondary electron signals to be obtained for different values of structural linewidth parameters from Monte Carlo simulations. Using the principle of the model-based library method, a model database of Monte Carlo-simulated SEM linescan profiles is thus constructed by varying the incident electron beam conditions and the grating linewidths; then, the grating linewidth is successfully characterized using experimental SEM images. The comparison with the TEM measurement reveals that the measurement accuracy is verified to within 0.3% for the linewidth of similar to 25 nm.

Since their discovery in 1981, quasicrystals have challenged traditional crystallography, showcasing the diversity of material structures. Quasicrystals are ordered structures in higher-dimensional Cartesian coordinate systems projected into lower dimensions. Exploring whether materials can grow into high-symmetry ordered structures in different mathematical coordinate systems is an intriguing topic. This paper reports a new crystallization growth mode in InSiO thin films, exhibiting high symmetry in spherical and cylindrical coordinate systems, named cylindrical symmetric rotating crystals (CSRC). These crystals show rotational symmetry in their lattice structure, consistent with cylindrical symmetry. They are also part of spherical crystals, which theoretically have one of the highest symmetries. Theoretical predictions suggest that a two-dimensional slice of a spherical crystal in conventional grating mode SEM images will display relatively complete Kikuchi patterns due to the wave properties of incident electrons, unlike crystals or quasicrystals, which show surface morphology from the particle properties of incident electrons. We formed InSiO CSRC by heating InSiO amorphous films and observed relatively complete Kikuchi patterns that quantitatively relate to the incident electron beam direction and energy. These findings align with theoretical predictions, indicating that the Kikuchi patterns in SEM images result from Bragg diffraction through coherent electron scattering within the crystals. Quantitative analysis of these patterns provides information on the lattice structure, constants, crystal orientation, stress information, defect concentration, and Brillouin zone of the InSiO material. This method of obtaining microstructural information directly from SEM images applies only to CSRC, not to conventional or quasicrystal samples.

Electron emission characteristics, mainly the intrinsic secondary electron yield, of an insulator material (glass SiO2) are studied by a Monte Carlo simulation method. In the modeling of electron inelastic scattering, we have employed the Levine-Louie (LL) dielectric function model together with optical energy loss function data for the description of electronic excitation and the Frohlich’s theory for the phonon scattering. In the modelling of electron elastic scattering, we have used Mott’s elastic scattering cross sections calculated with 384 scattering potential models. For the modelling of electron elastic scattering, we have used Mott elastic scattering cross sections calculated with 384 scattering potential models. It is found that the elastic scattering potential model has very strong impact to the simulated secondary electron yield but not to the backscattering coefficient. The theoretical uncertainty range for the Monte Carlo simulation of secondary electron emission yield for an oxide is thus much higher than that for an element. For certain selected potential models, the calculated secondary electron yields could be in a very good agreement with the experimental data. This sensitive character of the yield calculation to the choice of potential model allows the future determination of a reliable potential model when accurate experimental measurement data are available.

Black phosphorene (BP) is a glowing two-dimensional semiconducting layer material for cutting-edge microelectronics, with high carrier mobility and thickness-dependent band gap. Here, based on van der Waals (vdW)-corrected first-principles approaches, we investigated stacked BP/tin selenide (BP/SnSe) vdW heterostructure as an anode material for metal ion batteries, which exhibits a significant theoretical capacity, along with relatively durable binding strength compared to the constituent BP and SnSe monolayers. Our calculations demonstrated that the Li/Na adatom favors insertion into the interlayer region of BP/SnSe vdW heterostructure owing to synergistic interfacial effect, resulting in comparable diffusivity to the BP and SnSe monolayers. Subsequently, the theoretical specific capacities for Li/Na are found to be as high as 956.30 mAhg-1 and 828.79 mAhg-1, respectively, which could be attributed to the much higher storage capacity of Li/Na adatoms in the BP/SnSe vdW heterostructure. Moreover, the electronic structure calculations reveal that a large amount of charge transfer assists in semiconductor-to-metallic transition upon lithiation/sodiation, ensuring good electrical conductivity. These simulations verify that the BP/SnSe vdW heterostructure has immense potential for application in the design of metal-ion battery technologies.