We report for the first time the observation of bunching of monoatomic steps on vicinal W(110) surfaces induced by step up or step down currents across the steps. Measurements reveal that the size scaling exponent γ, connecting the maximal slope of a bunch with its height, differs depending on the current direction. We provide a numerical perspective by using an atomistic scale model with a conserved surface flux to mimic experimental conditions, and also for the first time show that there is an interval of parameters in which the vicinal surface is unstable against step bunching for both directions of the adatom drift.

In this paper, we investigate the antiband instability on vicinal Si(111) surfaces with different angles of misorientation. It is known that prolonged direct current-annealing of Si(111) results in the formation of antibands; i.e., the step bunches with the opposite slope to the primary bunches. We provide a theoretical description of antiband formation via the evolution of the atomic steps' shape. We also derive a criterion for the onset of the antiband instability under the conditions of sublimation controlled by slow adatom surface diffusion. We examine this criterion experimentally by studying the initial stage of the antiband formation at a constant temperature of 1270 • C while systematically varying the applied electromigration field. The experiment strongly supports the validity of the derived theoretical criterion and indicates the importance of accounting for the factor of critical field in the theoretical modeling of step bunching or antiband instabilities. Deduced from the comparison of theory and experiment, the Si surface atoms' effective charge cannot exceed double the elementary charge, set by the lower limit of kinetic characteristic length d s = 0.3 nm. Using d s = 1.7 − 4.5 nm draws values of the effective charge in line with the values reported in earlier studies.

a Highly regular step and terrace structures have been produced on surfaces of single crystalline MgO, miscut from the low-index (001) plane, upon annealing in air. Here, the evolution of the surface morphology of such surfaces is investigated. We demonstrate that the periodicity of these structures can be widely tuned in the submicron range by controlling the annealing conditions. Surface faceting resulted from annealing in the temperature range 1100-1580°C. The surfaces were characterized by atomic force microscope, X-ray diffraction, transmission electron microscope, and X-ray photoelectron spectroscopy to assess the role of contamination, temperature, and miscut angle in the final morphology. The presence of Al contamination in the post-annealed samples was found to be essential for the formation of the step and terrace structure. The stability of the resultant structures when exposed to ambient conditions is discussed. The cause of the apparent destruction of the surface morphology upon long-term atmospheric exposure has been identified, and a method to recover the faceted morphology is proposed. Overall, the study further facilitates the growth of nanostructures on such faceted surfaces.

This study has demonstrated, for the first time, the potential application of coatings to protect bricks or architectures against detrimental atmospheric effects via a self-cleaning approach. In this research, a facile fabrication method was developed to produce amorphous SiO2 particles and their hierarchical structures via applying trimethylchlorosilane (TMCS). They were fully characterized by various surface analytic tools, including a goniometer, SEM, AFM, zeta sizer, and a spectroscopic technique (FTIR), and then applied as super hydrophobic coatings on glass and sand. The characterization results revealed that the SiO2 particles are amorphous, quasi-spherical particles with an average diameter of 250–300 nm, and the hierarchical structures in the film were assembled from building blocks of SiO2 and TMCS. The wettability of the films can be controlled by changing the pH of the SiO2/TCMS dispersion. A super hydrophobic surface with a water contact angle of 165° ± 1° was achieved at the isoelectric point of the films. The obtained translucent super hydrophobic SiO2/TMCS coatings show good self-cleaning performances for glass and sand as construction materials. This study indicated that the superhydrophobic coatings may have potential applications in the protection of buildings and construction architectures in the future.