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[en] Stoichiometric HfO₂ films were atomic layer deposited from HfI₄ and HfCl₄ at 300 deg. C on p-Si(1 0 0) substrates. Water was in both cases used as an oxygen precursor. The films consisted dominantly of monoclinic HfO₂ phase. Additional tetragonal HfO₂ could be detected only in the films grown from HfCl₄. Effective permittivities were frequency-independent and varied in the range of 12-14, without clear dependence on the precursor used. Oxide rechargeable trap densities were relatively high for the films grown from HfCl₄. The films grown from HfI₄ were more resistant against breakdown. The films grown from either precursor contained 0.4 at.% of halide residues and 1.0-1.5 at.% hydrogen. Annealing in forming gas at 400 deg. C did not affect the film composition. The growth rate was somewhat more stable in the HfI₄ based process

[en] Hf-Si-O mixture films were fabricated by atomic layer deposition at 400 deg. C on Si(1 0 0) substrates. The deposition sequence for one hafnium silicon oxide submonolayer comprises surface reactions between Si(OC₂H₅)₄ and HfCl₄, followed by the hydrolysis step in order to effectively remove the residual ligands. The effective permittivity, leakage current, and capacitance-voltage behavior depended on the hafnium/silicon ratio and on the oxide/silicon interface quality. The dielectric quality can be modulated for various configurations of stacked layers with different hafnium to silicon ratios

[en] The detection efficiency of recoils with masses ranging from H up to Nb at energies from 0.05 to 1 MeV per nucleon has been investigated for Time-of-Flight Energy Elastic Recoil Detection (ToF-E ERD) systems. It is observed that the detection efficiency for the ToF-E detector telescope depends on the stopping power in the carbon foils, which in turn relies upon the recoil mass and energy. Furthermore, the limits of this behaviour depend on the setting of the discriminator thresholds. The detection efficiency of a time detector could be fitted to a universal curve that can be described by a simple empirical formula as a function of recoil electronic stopping power in the carbon foil. This formula can be used to predict the detection efficiency by recoil energy for N, O and other elements, for which it may not be easy to prepare suitable reference samples containing only that element

[en] Self-assembly is a phenomenon that continuously occurs at the nanoscale, as atoms form predetermined building blocks such as molecules and clusters, which then themselves gather into structures of a larger scale. The interplay of competing forces is a decisive factor in the emergence of these organized systems, but the precise mechanism by which this self-assembly progresses is seldom known. Using a combination of physical cluster deposition and atomic force microscopy, we have investigated the spontaneous formation of μm-sized rings of SiO_x-supported metal nanoclusters. With the help of molecular dynamics simulations, we show that the competition between short-range van der Waals attractions and long-range repulsive dipolar forces, induced by the ionic surface, plays a key role in the self-assembly of these structures. (paper)

[en] We study the effects of Ar⁺, He⁺ and C⁺ ion irradiation on multi-walled carbon nanotubes at room and elevated temperatures with transmission electron microscopy (TEM) and Raman spectroscopy. Based on the TEM data, we introduce a universal damage scale for the visual analysis and characterization of irradiated nanotubes. We show for the first time that the amount of irradiation-induced damage in nanotubes is larger than the value predicted for bulk materials using the simple binary collision approximation, which may be associated with higher defect production due to electronic stopping in these nanoscale systems. The Raman spectra of the irradiated samples are in qualitative agreement with the TEM data and indicate the presence of irradiation-induced defects. However, it is difficult to obtain quantitative information on defect concentration due to non-uniform distribution of defects in the nanotube films and in part due to the presence of other carbon nanosystems in the samples, such as graphitic crystallites and carbon onions.

[en] Ion irradiation of α-quartz renders the crystal SiO₂ structure amorphous. The enormous amount of structural defects produced after ion irradiation give a chance for photoactive intrinsic defects to be formed. These may be responsible for the photoluminescence in irradiated α-quartz. On the other hand, the radiation defects are not stable, and thus, an alternative structure where the defects of interest can be stabilized is required. The stabilization of the defects can be achieved in the structures of amorphous silica with embedded Si nanocrystals (NC), thanks to the unique structure of the formed interface. By means of Molecular Dynamics (MD), we analyze defects in both amorphized α-quartz and Si-NC/a-SiO₂ interfaces formed by 1.1, 2.4 and 4 nm diameter NC's. In the simulation, we employ a classical interatomic potential and a potential, which takes into consideration a charge transfer between Si and O atoms. We show that although the number of silanone bonds Si=O in irradiated quartz is higher, they are also found in a Si-NC/a-SiO₂ interface without the necessity of preceding irradiation of the sample. We also compare the defects in irradiation-amorphized quartz and the three sizes of Si-NC/a-SiO₂ interfaces. Analysis of the charges showed that the charge state of coordination defects depends on the type of atoms in the near neighborhood.

[en] NbN _x thin films were grown by the atomic layer deposition method using niobium chloride and ammonia as precursors. The deposition temperature was varied between 250 and 500 deg. C. The film properties were analyzed by energy dispersive X-ray spectroscopy, time-of-flight elastic recoil detection analysis, X-ray diffraction, and the standard four-point probe method. Additionally the diffusion barrier properties of approximately 10 nm thick NbN _x thin films deposited at 350, 400, and 500 deg. C were studied. As a comparison the barrier properties of Nb(Ta)N and Nb(Ti)N thin films deposited at 400 deg. C were studied. The breakdown temperatures of the annealed Cu/barrier/Si structures were determined from the X-ray diffraction data, sheet resistance values, and etch-pit results