[en] Ge nanoparticles fabricated by ion implantation technique in SiO₂ thin film crystallise after irradiation with a high-energy electron beam. The crystallisation process depends on the irradiation fluence and flux. Irradiation with a fluence above 6x10³ C/cm² results in cluster growth and above 4x10⁴ C/cm² in crystallisation. An irradiation with flux below 150 A/cm² leads to the crystallisation of Ge nanoparticles in the form of single crystals. For irradiation flux above this value the formation of twinned and multiply twinned particles (MTP) was observed

[en] A variation of the electric conductivity of island gold films with N-type current-voltage characteristics of the conductivity has been studied at the 0.2-35 keV electron bombardment. A non-monotonic dependence of the effect of the electron irradiation on the conductivity switching in the energy range from 0.7 to 0.8 keV and a decrease of its effectiveness with increasing voltage on the film are observed. The investigations performed enable us to propose the model in which a change-over from one to other branch of the current-voltage characteristic of the film conductivity with the resistance switching is attributed to adsorption and desorption of the adsorbate (water, a number of organic molecules etc.)

[en] Energy distribution of emitted electron, which position in energy range and shape are different for various mechanisms, was measured. Island gold films produced with thermal deposition in 10^-₆ torr vacuum on a glass substrate in a gap between gold electrodes were the object of the investigations. Electron emission appeared after the irreversible rearrangement of the film structure when introducing into them sufficiently high electric power. Electron emission was detected already at film voltage U=1.6-1.7 V however, the measurements were hampered due to low currents of an order I approximately 10^-₁₄ A, therefore the investigations were carried on at U=2-3.5 V when stable emission current exceeds 1O^-₁₃ A. The performed measurements of emitted electrons with the center of the island film show that the emission results from heating electron gas. Using the high-energy part of the distribution, which is the least sensitive to microfields, direct measurements of electron temperature in separate emission centers were performed and their sizes were evaluated

[en] Time-of-flight photoemission electron microscopy was used to measure spatially resolved energy distribution curves of electrons emitted from Ag nanoparticle films with different mass thicknesses. Two-photon photoemission (2PPE) was induced by femtosecond laser pulse excitation with 3.1 eV photon energy and 200 fs pulse width. Regions of Ag nanoparticles with different average sizes and one region with a continuous 100 nm thick Ag film were deposited as a stepped wedge on a Si(1 1 1) substrate. Upon laser excitation the nanoparticle films exhibit a very high electron emission yield in the images, whereas the uncovered Si surface and the continuous Ag film are dark. The time-of-flight electron spectra obtained from the nanoparticle films are remarkably different from the spectra of the continuous film, well-known from literature. The nanoparticle spectra are up to a factor of 160 more intense than the spectrum of the continuous film. They reveal different widths, overall shape and a shift and broadening of the Fermi edge. The results are discussed in terms of Mie plasmon assisted two-photon photoemission of the nanoparticles

[en] Full text: Many miniaturized functional units are operated periodically using high frequencies up to several GHz. A fast two dimensional trace of the surface fields on such devices could be helpful checking the function of sub-units and to find design lacks like local impedance mismatches. Photoemission electron microscopy (PEEM) was exploited to observe local ld distributions on microstrip-line devices with a best time resolution of 133 ps. A delayline detector served as imaging unit capable of a time resolving data acquisition processing. It replaces the conventional combination of phosphor screen and CCD-camera being equivalent to the ToF-PEEM described in. The setup can be operated at the resolution limit of the PEEM of about 20 nm while a continuous illuminating UV-lamp excites the photoelectrons in threshold photoemission. A pulsed photon source is not needed to obtain time resolved images, the time reference of the data acquisition was taken by a periodic signal in phase with the pulse pattern applied to the microstrip-line device. Ultra-short current pulses passing the microstrip-line are associated with local changes of the magnetic ld at the device surface and with a fast propagation of the electrical potential as well. The photoelectron imaging is immediately responding to small local field distortions due to the small kinetic energy of the electrons escaping the surface. Thus, local ld distortions can be detected as temporal changes between the 133 ps image-slices which are sorted by time in reference to the clock signal. The measurements were sampled over typically 10¹¹ clock cycles in order to collect enough statistics in all imaged time slices. Further, the dynamics in magnetic domain distributions on ferromagnetic surfaces can be visualized by means of circularly polarized X-ray photon excitation (MXCD)

[en] Photoemission electron microscopy was used to visualize the motion of magnetic domains on a sub-nanosecond timescale. The technique exploits the imaging of magnetic domains using soft X-ray circular dichroism, with the special feature that the instrument utilizes a fast image acquisition system with intrinsic 125 ps time resolution. The overall time resolution used is about 500 ps. Different domains and domain movements have been observed in lithographically-produced Permalloy structures on a copper microstrip-line. A current pulse of I=0.5 A with rise times of about 300 ps switched the Permalloy islands from a Landau-Lifshitz type domain configuration into metastable s-state domain configurations. A pulse with opposite direction could reverse these s-type patterns. Photoemission electron microscopy was employed to observe the domain movements while repeating current pulses passed the microstrip-line. Using small unipolar amplitudes, only the cross-tie walls of the s-type patterns disappear and the pattern becomes 'fuzzy', e.g. the domain rims are not sharp and some domains change their size. Before the structure switches at a current threshold, it is more fluctuating as shown by significant differences in sharpness of the islands rim and the inter-domain boundaries show. The device behavior complicates when a bi-polar pulse is applied. Switching and oscillating of domains is observed in various manners, e.g. very tiny domains appear and unify again

[en] The differences in the lattice dynamics of ZrO₂-Y₂O₃ solid solution particles are studied as a function of their size by means of slow-neutron inelastic scattering using the time-of-flight technique. As compared with massive state ZrO₂-Y₂O₃ solid solution particles of 190 A in size are characterized, firstly, by an increased density of normal vibrations in the 5-10 MeV low-frequency region caused by the contribution of low-frequency Rayleigh surface waves; secondly by intensification of the 55-70 MeV high-frequency spectrum region, associated with optical vibrations which is attributed to a decrease of disorder in oxygen sublattice experienced by small particles, which is characteristic of solid solution in massive state; thirdly, they are characterized by the fact, that the specific features of the vibration spectra, associated with high-symmetry points of the Brillouin zone, become less prominent since the contribution of the surface whose symmetry is lower than in the volume increases

No abstract available

[en] The present work is devoted to the more detailed studies of both the propagation of spin waves and the dynamics of 180 degree Neel walls movement during the magnetization

[en] Full text: Understanding the microscopic mechanisms of fast magnetic switching processes is of high fundamental as well as of vital technological importance. A particular challenge is the real-space mapping of the magnetization dynamics in complex magnetic systems in the picosecond regime. Soft x-ray photoemission electron microscopy (XPEEM) is known to be an extremely versatile tool to study static domain patterns in such systems, and can be straightforwardly extended into the time-domain by exploiting the intrinsic time structure of the synchrotron light. Our studies of microstructured Permalloy particles employ a magnetic pump - XPEEM probe approach involving microstripline samples. This set-up enabled us to follow the magnetization dynamics with a time resolution of Δ ≤ 10ps. The transient domain images exhibit a rich fine structure which depends strongly on the orientation of the local magnetization M-tilde with respect to the direction of the externally applied field pulse H-tilde(t). For a parallel or orthogonal orientation we find magnetization rotation and domain wall motion. For the antiparallel orientation between M-tilde and H-tilde(t), however, simple domain wall motion is blocked and an incoherent magnetization rotation occurs instead. This process leads to the formation of stripe-like magnetization patterns and vortices, the evolution of which is mapped along the rising edge of the field pulse. Along the trailing edge of the pulse we resolve characteristic relaxation phenomena, which lead to damped oscillations of the domain walls