Rutherford backscattering spectrometry

Abstract: We report the first successful preparation of thin films of Y‐Ba‐Cu‐O superconductors using pulsed excimer laser evaporation of a single bulk material target in vacuum. Rutherford backscattering spectrometry showed the composition of these films to be close to that of the bulk material. Growth rates were typically 0.1 nm per laser shot. After an annealing treatment in oxygen the films exhibited superconductivity with an onset at 95 K and zero resistance at 85 and 75 K on SrTiO3 and Al2O3 substrates, respectively. This new deposition method is relatively simple, very versatile, and does not require the use of ultrahigh vacuum techniques.

Abstract: Nonlinear least squares techniques have been applied to Rutherford backscattering spectrometry (RBS), allowing routine multivariable fits of simulated spectra to experimental data. Once a qualitatively correct simulation is made, this algorithm varies parameters of the simulation to obtain quantitative results. Optimization is done according to a maximum likelihood chi-squared definition, so that the best fit values of parameters and their uncertainties can be determined. Convergence of the algorithm is rapid for practical problems, allowing a typical four-variable fit to be accomplished in 30 seconds on a VAX 11/750. This algorithm allows confident treatment of spectra which might otherwise be considered too complex. An implementation of the algorithm is incorporated as part of an RBS analysis and simulation package, making it readily available for routine RBS analysis.

Abstract: The current status of Rutherford Backscattering Spectrometry (RBS) of surfaces and interfaces is reviewed. The reader is made familiar with the use of shadowing and blocking techniques for surface crystallography and with instrumental aspects of RBS. A formal theory of shadowing and blocking is presented, along with a variety of Monte Carlo methods for computer simulation of the shadowing and blocking experiments. The atomic geometries of various relaxed and reconstructed surfaces - clean and adsorbate covered - are surveyed and the performance of RBS on these surfaces is evaluated in comparison with other techniques for structure determination. Some attention is given to RBS investigations of adsorbate geometries and surface dynamical properties. The results are discussed in the light of recent theoretical predictions of surface structure and dynamics. The review further treats in-depth analysis of thin films and interfaces, prepared under UHV conditions. Topics to be addressed are (1) the growth mode of strained heteroepitaxial films, (2) the composition and morphology of thin metal films on silicon surfaces, (3) the initial stages of silicide formation, (4) the growth of oxide films, and (5) the atomic structure of bicrystal interfaces. The use of (near)-monolayer depth resolving power is shown to be essential in most of these studies. Emphasis is placed on fundamental aspects of interface formation, but possible technological applications are briefly mentioned too.

Abstract: ZnO:Al coatings were prepared by rf magnetron sputtering of ZnO together with dc magnetron sputtering of Al onto rapidly revolving unheated substrates under weakly oxidizing conditions. Optimized films had ∼1% luminous absorptance, ∼85% thermal infrared reflectance, and ∼5×10−4 Ω cm electrical resistivity at a thickness of ∼0.3 μm. The Al content was ≲2 at. %, as determined by Rutherford backscattering spectrometry. Transmission electron microscopy and electron diffraction showed ∼50‐nm average crystallite size and a hexagonal wurtzite structure. Spectrophotometric transmittance and reflectance were recorded in the 0.2–50‐μm wavelength interval, and the complex dielectric function was evaluated by computation. The optical data were explained from an effective mass model for n‐doped semiconductors. The Al atoms are singly ionized, and the associated electrons occupy the bottom of the conduction band as free‐electron gas. The Al ions act as pointlike Coulomb scatterers and are screened by the electrons acco...

Abstract: The evolution of radiation-induced damage in fully-stabilized, cubic zirconia (FSZ) (Y, Ca and Er dopants acting as stabilizers) and in pure, unstabilized, monoclinic zirconia, was investigated using Rutherford backscattering spectrometry and ion channeling (RBS/C), along with X-ray diffraction and transmission electron microscopy (TEM). FSZ crystals were irradiated with 340–400 keV Xe++ ions and at temperatures ranging from 170 to 300 K, or with 127I+ ions (72 MeV) at temperatures ranging from 300 to 1170 K. No amorphization of zirconia was found under any irradiation condition, though in the case of 72 MeV I+ ion irradiations, the irradiation-induced defect microstructure was observed to produce dechanneling effects in RBS/C measurements that reach the `random' level. Damage accumulation in Xe-ion irradiation experiments on FSZ crystals was found to progress in three stages: (1) formation of isolated defect clusters; (2) a transition stage in which damage increases rapidly over a small range of ion dose, due to the linking of dislocations and defect clusters; and (3) a `saturation' stage in which damage accumulation is retarded or increases only slowly with ion dose. The FSZ crystal composition does not seem to alter significantly the dose-dependence of these damage stages. Unstabilized, monoclinic ZrO2 was observed to transform to a higher symmetry, tetragonal or cubic phase, upon 340 keV Xe++ ion irradiation to Xe fluences in excess of 5×10 18 m −2 (dose equivalent, ∼2 displacements per atom or dpa) at 120 K. This transformation was accompanied by a densification of the ZrO2 phase by ∼5%. No amorphization of the pure ZrO2 was observed to a Xe++ ion fluence equivalent to a peak displacement damage level of about 680 dpa.