Structure And Composition Of Amorphous Ge1-xsnx Thin Films

The composition and bonding configuration of amorphous germanium-tin (a-Ge1-xSnx) thin films are reported (0≤x<0.3). Mössbauer spectroscopy analyses show that under the reported deposition conditions all tin atoms enter the a-Ge network in a perfect substitutional way, i.e., in a covalent tetrahedral configuration. The absence of defect structures in the tin sites is discussed and compared with results on films prepared under different conditions.63115596559

An analytical energy loss line shape for high depth resolution in ion beam analysis

The knowledge of the energy loss distribution in a single ion atom collision is a prerequisite for subnanometric resolution in depthprofiling techniques such as nuclear reaction profiling NRP and medium energy ion scattering MEIS . The usual Gaussian approximation specified by the stopping power and energy straggling is not valid for near surface regions of solids, where subnanometric or monolayer resolution can be achieved. In this work we propose an analytical formula for the line shape to replace the usual Gaussian distribution widely used in low resolution ion beam analysis. Furthermore, we provide a simple physical method to derive the corresponding shape parameters. We also present a comparison with full coupled channel calculations as well as with experimental data at nearly single collision condition

Mössbauer Study Of Hydrogenated Amorphous Germanium-tin Thin-film Alloys

This work reports on the structure of defects around Sn atoms in amorphous germanium-tin alloys deposited by the rf sputtering of compound targets. The influence of atomic hydrogen on the structure of such defects is reported for the first time. The samples were analyzed by Rutherford backscattering spectrometry and conversion electron Mössbauer spectroscopy. The main conclusion of this research is that, besides the known substitutional position of Sn atoms in the a-Ge network, a new Sn bonding configuration appears, which may be at the origin of the degradation of the optoelectronic properties of the alloy found experimentally. This new configuration is an octahedrally coordinated Sn atom resulting from the trapping of Ge vacancies by Sn atoms, the energetically favored final site being the tin atom in the center of the Ge relaxed divacancy.6652083209

Influence Of The Chemical Surface Structure On The Nanoscale Friction In Plasma Nitrided And Post-oxidized Ferrous Alloy

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Friction is a ubiquitous phenomenon in everyday activities spanning from vehicles where efficient brakes are mandatory up to mechanical devices where its minimum effects are pursued for energy efficiency issues. Recently, theoretical models succeed correlating the friction behavior with energy transference via phonons between sliding surfaces. Therefore, considering that the energy losses by friction are prompted through phonons, the chemical surface structure between sliding surfaces is very important to determine the friction phenomenon. In this work, we address the issue of friction between a conical diamond tip sliding on different functionalized flat steel surfaces by focusing the influence of the chemical bonds in the outermost layers on the sliding resistance. This geometry allows probing the coupling of the sharp tip with terminator species on the top and underneath material surface at in-depth friction measurements from 20 to 200nm. Experimentally, the friction coefficient decreases when nitrogen atoms are substituted for oxygen in the iron network. This effect is interpreted as due to energy losses through phonons whilst lower vibrational frequency excitation modes imply lower friction coefficients and a more accurate adjustment is obtained when a theoretical model with longitudinal adsorbate vibration is used.10511CAPES; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior; FAPERGS; Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Holmberg, K., Andersson, P., Erdemir, A., (2012) Tribol. Int., 47, p. 221Sabeur, M., Ibrahim, D., Mohamed, E.M., Hassan, Z., (2013) Tribol. Int., 59, p. 240Holmberg, K., Matthews, A., (2009) Coatings Tribology: Properties, Mechanisms, Techniques and Applications in Surface Engineering, , (Elsevier)Cannara, R.J., Brukman, M.J., Cimatu, K., Sumant, A.V., Baldelli, S., Carpick, R.W., (2007) Science, 318, p. 780Persson, B.N.J., Bucher, F., Chiaia, B., (2002) Phys. Rev. B, 65, p. 184106Krim, J., (2012) Adv. Phys., 61, p. 155Erdemir, A., (2005) Surf. Coat. Technol., 200, p. 1792Erdemir, A., Li, S., Jin, Y., (2005) Int. J. Mol. Sci., 6, p. 203Oliver, W.C., Pharr, G.M., (1992) J. Mater. Res., 7, p. 1564Blau, P.J., (2009) Friction Science and Technology: From Concepts to Applications, , (CRC Press)Mo, Y., Turner, K.T., Szlufarska, I., (2009) Nature, 457, p. 1116Lewis, S.P., Pykhtin, M.V., Mele, E.J., Rappe, A.M., (1998) J. Chem. Phys., 108, p. 1157Persson, B.N.J., Tosatti, E., Fuhrmann, D., Witte, G., Wöll Ch., (1999) Phys. Rev. B, 59, p. 11777Shi, Y.-J., Du, Y.-L., Chen, G., (2013) Comput. Mater. Sci., 67, p. 341Niewa, R., Rau, D., Wosylus, A., Meier, K., Hanfland, M., Wessel, M., Dronskowski, R., Schwarz, U., (2009) Chem. Mater., 21, p. 392Isida, S., Suzuki, M., Todo, S., Môri, N., Siratori, K., (1996) Physica B, 219-220, p. 638Ochoa, E.A., Wisnivesky, D., Minea, T., Ganciu, M., Tauziede, C., Chapon, P., Alvarez, F., (2009) Surf. Coat. Technol., 203, p. 1457Roberts, W.L., (1990) Encyclopedia of Minerals, , (Chapman & Hall)Chertihin, G.V., Andrews, L., Neurock, M., (1996) J. Phys. Chem., 100, p. 14609Shebanova, O.N., Lazor, P.J., (2003) Solid State Chem., 174, p. 42

The Structure Of Defects In Amorphous Germanium Tin-alloys

This work reports on the structure of defects around Sn atoms in amorphous germanium-tin alloys. The influence of atomic hydrogen on the density of such defects is reported. The samples were deposited by rf sputtering compound targets, and analized by Rutherford backscattering spectrometry and conversion electron Mössbauer spectroscopy. Besides the known substitutional position of Sn atoms in the a-Ge network, a new octahedrally bonded Sn configuration appears resulting from the trapping of Ge vacancies by Sn atoms. © 1989.114PART 2558560Chambouleyron, Marques, (1989) J. Appl. Phys., 65, p. 1591I. Chambouleyron, F.C. Marques, I. Baumvol, and R. Barrio, J. Appl. Phys. (in print)Nanver, Weyer, Deutsch, (1982) Z. Phys., 47 B, p. 103Stevens, Stevens, (1978) Mössbauer Effect Data Index, , Plenum, N

Solved and unsolved problems in ion beam analysis the influence of a single collision

In this work we explore some unsolved problems in ion beam techniques involving backscattered projectiles or nuclear reactions. In particular, we focus on the influence of a single violent collision on the depth resolution. In high resolution experiments, where the surface or near surface interfaces are investigated, the energy straggling becomes very asymmetric. The corresponding energy loss distributions are skewed for larger energy losses due to the ionization and excitation of the inner shell electrons. We determine the electronic energy loss distribution using the coupled channel calculations. Then these ab initio calculations are used as benchmark for simple models of energy loss lineshapes that can be used in ion beam analysis to replace the standard Gaussian distributio

Advanced ion energy loss models Applications to subnanometric resolution elemental depth profiling

In principle, the depth distribution of the different chemical elements near the surface of solids can be determined quantitatively and absolutely with subnanometric depth resolution using medium energy ion scattering MEIS , which is a refined version of Rutherford backscattering spectrometry RBS . The energy resolution of current MEIS analyzers reveals spectral features that cannot be resolved using conventional RBS detectors. Thus, the usual data analysis framework based on a standard Gaussian approximation for the ion energy distribution in the target is applicable to regular RBS, but not generally to MEIS, in particular if one aims at subnanometric depth resolution. The observed asymmetry in the ion energy loss distributions is a direct consequence of the asymmetric character of inelastic energy transfers during individual atomic collisions and of the stochastic character of the resulting energy losses. We propose a model that accounts for the proper statistics of the small energy loss events and for an approximate electronic energy loss distribution during the backscattering event. The validity of this model is discussed and applied to the determination of HfO2 and TiO2 film thicknesses as well as to detect Al2O3 and HfO2 intermixing. This final application case also illustrates the potentialities as well as some inherent limitations of MEIS. The model developed here has been made available to the public in the form of a software for MEIS data analysi

Magnetic And Structural Properties Of Ion Nitrided Stainless Steel

The magnetic properties and crystalline structure of expanded austenite obtained by ion beam nitriding of AISI 316 steel are investigated. Magnetic force microscopy reveals that the nitrogen expanded austenite has two different layers, an outermost ferromagnetic layer and a paramagnetic layer beneath it. Superimposing the nitrogen concentration profile determined by secondary neutral mass spectrometry and the magnetic force microscopy image, one can see that the paramagnetic-ferromagnetic transition takes place at the inflection point of the nitrogen concentration profile at about 14±2 N at. %. Conventional and glancing angle x-ray diffraction suggests that nitrogen could occupy first tetrahedral interstitial positions (nitrogen-poor paramagnetic phase) and then, after saturation of Cr traps, octahedral interstitial positions (nitrogen-rich ferromagnetic phase). 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Sequential thermal treatments of SiC in NO and O2: Atomic transport and electrical characteristics

Sequential thermal oxidations and oxynitridations of SiC were performed using O218 and NO. The resulting films were characterized by x-ray photoelectron spectroscopy, ion beam analyses, and capacitance-voltage measurements. The best electrical characteristics were obtained from films directly grown in NO. A subsequent oxidation in O2 degraded the interface due to negative flatband-voltage shift, removal of N, and formation of C compounds, while a further annealing in NO brought the flatband shift in the C-V curves to rather moderate figures. This shift is related to competitive processes taking place during dielectric film formation which are discussed