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This work illustrates the impact of atmospheric gases on the surface of epitaxial graphene. The different rate of adsorption on different parts of graphene samples provides a concrete evidence that the surface morphology of graphene plays a significant role in this process. The uneven adsorption occurs only on the surface of the monolayer graphene and not on bilayer graphene. The second monolayer is distinguished and verified by the phase contrast mode of atomic force microscopy and the low energy electron microscopy, respectively. Raman spectroscopy is used to study the strain on the surface of graphene; results indicate that monolayer and bilayer graphene exhibit different types of strain. The bilayer is under more compressive strain in comparison with monolayer graphene that hinders the process of adsorption. However, the wrinkles and edges of steps of the bilayer are under tensile strain, hence, facilitate adsorption. Samples were subjected to X-ray photoelectron spectroscopy which confirms that the adsorbates on the epitaxial graphene are carbon clusters with nitrogen and oxygen contamination. For reversing the adsorption process the samples are annealed and a method for the removal of these adsorbates is proposed.

The magnetic properties of ultrathin ferromagnetic films are studied by means of Spin Polarized Low Energy Electron Microscopy. Measurements of the onset of ferromagnetic order, distribution and shape of magnetic domains, magnetization direction and their change are now well established standards for this technique. Here, the asymmetry parameter has been determined as a function of film coverage and energy of the incident electron beam. It reveals oscillatory behavior which is usually described as due to the quantum size effect (QSE). We explore the origin of the characteristic features observed in the asymmetry curves and distinguish between the QSE oscillations and other phenomena influencing the shape of the asymmetry curves. As an example we discuss the asymmetry of ultrathin iron films grown on the W(1 1 0) surface.

Thin, stable and inert dielectric spacers are essential for manufacturing electronic devices based on 2D materials. However, direct synthesis on top of 2D materials is difficult due to their inert nature. In this work, we studied how an electron beam induces fragmentation of borazine and enables spatially confined synthesis of amorphous-BNx on graphene at room temperature. Using a combination of X-ray Photoelectron Spectroscopy, Low Energy Electron Microscopy, and Scanning Tunneling Microscopy we studied the morphology of the heterostructure, its chemical composition, and finally its temperature evolution. We find that electron-beam induced deposition starts by the binding of heavily fragmentized borazine, including atomic boron, followed by the growth of a multilayer with a 1:0.7 B:N ratio. The final structure exhibits a thermal stability up to 1400 K and ~ 50 nm spatial control provided by the electron beam. Our studies provide surface science insight into the use of electron beams for synthesis and lateral control of stable and inert layers in 2D heterostructures.

The structural and electronic properties of Pt induced nanowires on Ge(110) surfaces have been studied by scanning tunneling microscopy and low energy electron microscopy. The deposition of a sub-monolayer amount of Pt and subsequent annealing at 1100 (±30) K results into nanowires which are aligned along the densely packed [1–10] direction of the Ge(110) surface. With increasing Pt coverage the nanowires form densely packed arrays with separations of 1.1 ± 0.1 nm, 2.0 ± 0.1 nm and 3.4 ± 0.1 nm. Ge pentagons reside in the troughs for nanowire separations of 3.4 nm, however for smaller nanowire separations no pentagons are found. Spatially resolved scanning tunneling spectroscopy measurements reveal a filled electronic state at −0.35 eV. This electronic state is present in the troughs as well as on the nanowires. The −0.35 eV state has the strongest intensity on the pentagons. For Pt depositions exceeding two monolayers, pentagon free nanowire patches are found, that coexist with Pt/Ge clusters. Upon annealing at 1040 K these Pt/Ge clusters become liquid-like, indicating that we are dealing with eutectic Pt0.22Ge0.78 clusters. Low energy electron microscopy videos reveal the formation and spinodal decomposition of these eutectic Pt/Ge clusters.

Progress in materials science is inseparably connected with development of new analytical methods which make possible to observe the materials microstructure with high sensitivity. The aim of the present study is shown that scanning low energy electron microscopy (SLEEM) has a significant impact in advance of a fundamental understanding of the evolution of microstructure upon semi-solid processing. This paper deals with the application of the ultra high vacuum scanning low energy electron microscopy (UHV SLEEM) to the study of microstructure of X210Cr12 steel after the formation in semi-solid state and the study of the annealing of deformed metastable austenite. Examples from these specimens show that the contrast between differently oriented grains in polycrystalline materials is very sensitive to the parameters such as energy of the primary beam, working distance and detection of high angle backscattered electrons.

We report a study on the spatial homogeneity and nitridation of a nanopattern template using a spectroscopic photoemission and low energy electron microscopy. The template was composed of Al nanodots which were patterned into a SiO2/Si(1 1 1) surface using e-beam lithography and reactive ion etching. The template exhibited a global inhomogeneity in terms of the local topography, Al composition and structure of the individual nanopatterns. After nitridation, the individual nanopatterns were diminished, more corrugated and faceted. The nitridated nanopatterns were structurally ordered but differently orientated. The nitridation effectively removed the fluorine contaminants by decomposition of the fluorocarbon sidewalls, resulting in the AlN nanopatterns and partially nitridated Si substrate surface outside the nanopattern domains.

The unique properties of graphene can vary greatly depending on the number of graphene layers; therefore, spatial control of graphene thickness is desired to fully exploit these properties in promising new devices. Using low energy electron microscopy (LEEM), we investigate how scratches on the surface of 6H–SiC(0 0 0 1) affect the epitaxial growth of graphene. Oscillations in the LEEM-image intensity as a function of electron energy (I–V LEEM analysis) show that the number of graphene layers clearly differs between regions of scratched and smooth substrate. The extent of the thicker graphene layers formed above scratches is found to be significantly larger than the width of the scratch itself. This finding can be implemented as an additional technique for spatially modulating graphene thickness.

A SPLEEM (spin polarized low energy electron microscope) has been designed with a numerical simulation of electrostatic and magnetic field distributions and electron ray trajectories. Highly (more than 90%) spin polarized electron source has been used. A Wien type spin manipulator and a magnetic lens type spin rotator are used to align spin direction. A magnetic field free objective lens is designed to observe magnetic domain structure of magnetic materials. High or low magnification mode can be selected by using a combined electrostatic and magnetic objective lens for a high spatial resolution and a wide imaging area observation. An electrostatic mirror aberration corrector is installed after the image forming objective lens. A double deflection 45° beam separator is used to bend the direction of electrons from the source to the objective lens and from the objective lens to the mirror aberration corrector.

We have applied the spectroscopic photoemission and low energy electron microscope to study high- k gate dielectrics and have performed the following in situ operations during ultrahigh vacuum annealing: real-time observation of surface morphology and microregion photoelectron spectroscopy measurements. Changes in surface morphology and electronic states were consistent with the models previously reported in the case of HfO 2 /Si. No clear differences between void regions and nonvoid regions have been observed in microregion photoelectron spectra for poly-Si/HfO 2 /Si, regardless of phase separation in real space. These results have suggested that the initial void formation occurs in about 100-nm wide regions for both HfO 2 /Si and poly-Si/HfO 2 /Si.

The backscattering coefficient of 1–4 keV electron and positron beams normally incident impinging on Al thin film targets is stochastically modeled within a Monte Carlo frame work. The aim of the present paper is to study the behavior of the backscattering coefficient as a function of the Al film thickness. To the authors’ knowledge, no theoretical or experimental work on the dependence of the positron backscattering coefficient on film thickness targets has been reported so far. It is found that the backscattering coefficient for both electron and positron beams presents different behaviors when the Al film thickness belongs to the nano-scale. Beyond this scale, the behavior becomes qualitatively similar.

Two aspects of low-dimensional magnetism are discussed: the spin-dependent quantization effects in perfect two-dimensional single crystal layers and the magnetic domain structure of submicron magnetic patterns. Both require high lateral resolution and surface sensitivity. This is provided by spin-polarized low energy electron microscopy (SPLEEM) and X-ray magnetic circular dichroism photoemission electron microscopy (XMCDPEEM).

Low energy electron microscopy (LEEM) is used to study the quantum size effect (QSE) in electron reflectivity from thin films. Strong QSE interference peaks are seen below 20 eV for Cu and Ag films on the W(1 1 0) surface and Sb films on the Mo(0 0 1) surface. Simple inspection of QSE interference peaks reveals that all three metals grow atomic layer-by-atomic layer. Layer-specific I ( V ) spectra obtained with LEEM permit structural analysis by full dynamical multiple scattering LEED calculations for a layer-by-layer view of thin film structure.

The Ti/6H-SiC(0001) interface with the Schottky limit and the SiC surfaces before metallization are investigated using low energy electron microscopy (LEED), Auger electron spectroscopy (AES), X-ray photoemission spectroscopy (XPS), scanning tunneling microscopy (STM), and cross-sectional transmission electron microscopy (TEM). The surface to form the resultant Schottky limit is prepared by dipping the SiC wafer into pure boiling water of ∼100°C for 10 min. The surface has the 1×1 surface reconstruction with a small amount of oxygen less than 5%, suggesting that the surface is mainly terminated by hydrogen. In the STM analysis, we found that oxygen strongly terminates atomic step edges, which leads to the drastic reduction of the resultant density of interface states after metallization at room temperature. Epitaxial and commensurate relations between a Ti layer and the SiC substrate without any interface layer were found by cross-sectional TEM analysis. The observed commensurate interface indicates that the surface hydrogen terminator on the terraces was desorbed after metallization.

The growth and melting transition of Pb clusters on the Cu(111) surface have been studied with low energy electron microscopy. Kinetic growth and equilibrium cluster shapes are distinguished and a systematic variation of the melting temperature among individual clusters in an ensemble has been observed. A simple thermodynamic model is proposed which accounts for this unusual melting behaviour through known finite size and new interface effects. The role of the interface roughness, e.g. atomic steps, in modifying the interface tension between adsorbate and substrate is suggested by these results.