Publications

Structure of metal clusters and of the C-60 matrix in Au/C-60 and Cu/C-60 nanosystems was investigated by X-ray diffraction. Results support a charge-transfer-type interaction at the metal-C-60 interface, which affects the size distribution of metal clusters: favouring interstitial location of metal ions in the fullerite lattice.

We calculate the orbital magnetization of a confined 2DEG as a function of the number of electrons in the system. Size effects are investigated by systematically increasing the area of the confining region. The results for the finite system are compared to an infinite one, where the magnetization is calculated in the thermodynamic limit. In all calculations the electron-electron interaction is included in the Hartree approximation. (C) 2000 Elsevier Science B.V. All rights reserved.

AlN films have been deposited by RF (1.78 MHz) and DC reactive magnetron sputtering (argon and nitrogen) on glass substrates at low temperatures (< 150 degrees C) and with 16, 21 and 30% nitrogen ratios. We have found optically and structurally distinguishable characteristics for films (both opaque and transparent), obtained using these two experimental methods. We suggest that these differences are due to plasma effects in the substrate during growth, resulting from the different ionic bombardment rates of the two sputtering modes. (C) 2000 Elsevier Science S.A. All rights reserved.

The trapping levels induced in p-n Si junctions by irradiation with 24 GeV proton were investigated using Thermally Stimulated Currents (TSC) methods in the 90-300 K temperature range. Several trapping levels, with activation energies between 0.27 and 0.57 eV, were put into evidence. The spatial distribution of the traps was investigated using different wavelengths for the light used to fill the traps. The results lead to the conclusion that the deepest trapping levels are not uniformly distributed in the volume of the sample. For the most important trapping level the average introduction rate was estimated to 0.9-1.2 cm(-1). The activation energy and the capture cross-section of this trapping level seems to depend on the impurity element introduced in Si. (C) 2000 Elsevier Science B.V. All rights reserved.

Optical charging spectroscopy (OCS) is first time reported as applied to p-n junctions. The existence of one deep trapping level for electrons and two deep trapping levels for holes was put into evidence, using this method, in proton irradiated p(+)-n-n(+) silicon structures. An analytical formula for the OCS discharging current for this type of structures was deduced. (C) 2000 Elsevier Science B.V. All rights reserved.

The experimental data carried out by Mossbauer and magnetic resonances investigations of the structural phase transitions in K2ZnCl4 crystals are discussed by a simple electrostatic model, calculating, the lattice contributions to the local electric potential V(r), electric field intensity E(r) a,nd electric field gradient tensor, V-alpha beta(r) and taking into account both the fractional electric point charges and rigid lattice approximations. The validity of the model is proved by a good fit of the computing results and experimental data of quadrupole splitting parameters at K Bites obtained by K-39-NMR methods in high temperature incommensurate phase (similar to Pnam symmetry). The experimental results obtained by Mossbauer and EPR methods in commensurate phase (Pna2(1) symmetry) of iron and copper doped K2ZnCl4 crystals are explained by relaxing the rigid lattice approximation. The insertion of probe ions appear to be done on not-exactly-Zn2+ site.

The crystal field disorder in some trigonal germanates of the type X(3-y)Ln(y)Fe(2+y)Ge(4-y)O(14) (X = Ba, Sr; Ln = La, Nd; y = 0, 1) is studied by Fe-57 Mossbauer effect. The dispersion of the electric field gradient (EFG) at the octahedral sites of these compounds is investigated. A correlation of the experimental and calculated EFG data with some crystal-chemistry aspects is presented.

The resolution-intensity antinomy is herewith represented by the Experimental performance criterion - luminosity factor couple. The experimental performance criterion, in close relationship but not identical with the resolution, is an entity connected with the object of the experiment. It is proposed as an attempt to introduce a kind of worth-scale for the results of experiments performed with a certain instrument. This concept is used in computer simulation of experiments performed at both thermal neutron - and synchrotron radiation - sources, for determination of the most convenient instrumental parameters of powder diffractometers.

When a magnetic field is applied on a narrow gap semiconductor with high hole mobility, a substantial rise in the figure of merit can be observed due to Ethinghausen effect. The most important proof of this effect was achieved by using Bi-Sb alloys. The present paper is devoted to performance of the electrochemical synthesis of Bi-Sb alloys from acid aqueous solutions and to the investigations of physico-chemical. properties of these alloys. Thick films of Bi-Sb alloy were electrodeposited from both chloride and perchlorate solutions. The electro-deposited films obtained from perclorate solutions are thicker, more compact and more uniform. The Bi/Sb ratio in the solution bulk was found to be approximately the same to the Bi/Sb ratio in the electrodeposited alloy. The Hall effect was measured by a home-made apparatus. The range of the magnetic field (B) determined by a standard induction coil was 0.05-1 T. Carrier concentration, n is 10(18) cm(-3) and increases slow in the choosen magnetic range.