Creation Of Surface Nanostructures Research Articles

Creation of surface nanostructures in lanthanum fluoride single crystals by irradiation with slow highly charged ions

Slow highly charged ions (HCI) were utilized successfully for the formation of various nanostructures in the surfaces of different materials. The creation mechanism of HCI-induced nanostructures was intensively studied in alkali- and alkaline-earth fluorides. Here, we are investigating another type of fluorine-containing ionic crystals of different crystalline and electronic structure, namely lanthanum fluoride, LaF3. The single crystals were irradiated with slow (eV-keV) highly charged xenon ions from an Electron Beam Ion Trap. After irradiation, the crystals surfaces were investigated by scanning force microscopy. The measured topographic images show nanohillocks emerging from the surface. These nanostructures were observed only after exceeding a well-defined threshold in the potential energy. The role of ion parameters for nanohillocks formation as well as a comparison with results for swift heavy ion irradiations of LaF3 single crystals are presented. Furthermore, the similarities and differences between LaF3 and other ionic fluoride crystals, in the creation of surface nanostructures, are discussed.

Diffusion Temperature Dependence in Tilted Periodic Potentials Ranging from Underdamped Systems to Overdamped Systems

Recently, both the experimental data and the data of theoretical research appeared stating that the diffusion coefficient shows nonmonotonic behavior with temperature. The motion of Brownian particles in the space periodic structures is an example of the systems with abnormal temperature dependence of the diffusion. The aim of the work was to study the change in the temperature dependence of the diffusion coefficient with a change in friction, both in underdamp and overdamped systems. This scientific paper studies the diffusion of particles in tilted spatial-periodic potentials in a wide temperature range. It is shown that in both underdempted and overdamped systems, the diffusion coefficient reaches a maximum value for a certain value of an external force, the value of which depends on the value of the friction coefficient. However, in systems with low and high friction, the temperature dependence of the diffusion coefficient differs. It was established that the systems with a low friction level γ’ show temperature abnormal diffusion (TAD) at which the diffusion coefficient D is increased with a decrease in temperature. At the same time, the diffusion is enhanced at high γ values with the rise in temperature. This scientific paper studies the transition procedure from the exponential dependence of TAD to the ordinary power temperature dependence with an increase in γ’. It was shown that the energy hump that separates “running” solutions and “localized” solutions is decreased with an increase in the friction coefficient and it vanishes at γ -> 0 . Simultaneously with a decrease in ε, the temperature interval of the TAD also narrows. It was established that the temperature-limited TAD domain appears in the region of intermediate values of the friction coefficient. In a specified force range the diffusion coefficient is first increased with a decrease in temperature and then it begins to decrease again. The diagrams of existence of such domains have been constructed. The results obtained opens up prospects for the creation of new technologies for managing diffusion processes. This is of great importance for the production of nanomaterials with a given structure, the creation of surface nanostructures, etc.

Creation of surface nanostructures in Al2O3 by slow highly charged ions

Al2O3 single crystals were irradiated with slow highly charged Xe ions of various charge states from an EBIT (Electron Beam Ion Trap) source at the Dresden two source facility. The irradiations were performed at room temperature and under normal incidence. Scanning force microscopy (SFM) was utilized to investigate the topography of the irradiated surfaces. The measurements showed that above a potential energy threshold, each ion creates a nanohillock protruding from the surface. These structures are compared to those created by swift heavy ions (SHI). The results are discussed in terms of potential energy deposition of highly charged ions (HCI) and electronic energy loss of SHI.

Nanostructuring of BaF 2 (1 1 1) surfaces by single slow highly charged ions

The creation of surface nanostructures in BaF 2 (1 1 1) surfaces was studied after irradiation with slow highly charged Xe ions from the Dresden-EBIT (electron beam ion trap). After irradiation, the crystals were investigated by scanning force microscopy (SFM). Using specific ion parameters, the topographic images show nanohillocks emerging from the surface. Additionally, we used the technique of selective chemical etching to reveal the lattice damage created by ion energy deposition below and above threshold needed for surface hillocks formation. The role of both potential and kinetic energy as well as a comparison with results for swift heavy ion irradiations of BaF 2 single crystals are presented.

Creation of surface nanostructures by irradiation with slow, highly charged ions

It has recently been demonstrated that slow (v < < 1 a.u.) highly charged ions (HCIs) are able to generate nano-sized hillocks on cleaved CaF2(1 1 1) surfaces. The aim of the present study was to explore whether surface nanostructures can also be formed on other target materials by the impact of slow HCIs. To this purpose, we have irradiated LiF(0 0 1), diamond-like carbon (DLC) and Au(1 1 1) with slow Xe HCIs (up to charge state 44+) from the Heidelberg electron beam ion trap. After irradiation, the crystals were investigated by scanning force microscopy. Nanometric hillocks protruding from the surface were found in the topographic images for the case of Xe q+ on LiF(0 0 1) for charge states q ≥ 28, but not for DLC and Au(1 1 1).