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  • Polymer and Materials Science  (9)
  • 1
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Auger electron spectroscopy has been used to characterize the oxidation of polycrystalline zirconium in an oxygen atmosphere at low pressures (10-8 ≤ Po2 ≤ 10-5 Torr) and room temperature after cleaning the surface by Ar+ -ion bombardment. Quantitative analysis of the oxidation process was performed by using the intensity of the Zr(M45N23N45) line which is characteristic of the metallic zirconium. It is concluded from this work that oxidation proceeds as follows: (i) dissociative chemisorption for oxygen exposures lower than 2 L; (ii) formation of nuclei of oxide which grow until coalescence for exposures between 2 and 60 L; (iii) thickening of the oxide film grown in the previous stage. A limiting thickness of 1.5-2 nm is estimated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Tantalum silicide films of ∼200 nm thick and composition TaSi2 were obtained by co-sputtering in a Varian 3120 S-gun magnetron system. The films were then introduced in an AES spectrometer and bombarded with Ar+ ions of different energies in order to obtain surfaces of different compositions as a consequence of preferential sputtering effects and their dependence on the energy of the primary ions. Lowering the energy of the Ar+ ions resulted in surfaces very rich in tantalum. The interactions of these surfaces with oxygen at low pressures (10-8-10-5 Torr) and at room temperature then have been studied comparatively by Auger electron spectroscopy. Reference experiments with pure Si and Ta allowed the comparison with those of the different silicide surfaces. It is found that the oxygen uptake depends on the Ta content so that the richer in Ta the surface is, the higher the O2 incorporation. Furthermore, the uptake rate at the different TaSix surfaces resembles better the measured rate for pure Ta than that observed for pure Si. It has been observed also that the oxidation of Si is enhanced over that of pure silicon in all the surfaces studied here. Besides, the enhancement depends on the tantalum content.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 15 (1990), S. 675-680 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The electron energy-loss spectra (EELS) associated with 4f and 5p excitations, and the secondary electron spectra (SES) have been used to study the oxidation of a clean polycrystalline tantalum surface. For the clean and oxygen-exposed surfaces, the EELS results are discussed in terms of bulk and surface plasmons as well as interband transitions to unoccupied states above the Fermi level (EF). The secondary electron spectra have been used as a fingerprint for the density of unoccupied states above EF. The changes observed in the EEL spectrum upon oxygen exposure are explained as being due to oxide formation, in agreement with previous results by XPS and AES. The features observed above the NVV and OVV Auger transitions, in both the clean and oxidized surfaces, are described as auto-ionization emission due to the decay of electrons that have been excited resonantly from the 4f and 5p levels to states well above the states well above the Fermi energy. The excitation process has been identified also in the EEL spectra.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 809-813 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: In this work BN films have been deposited by the plasma-enhanced chemical vapour deposition (PECVD) technique on p-type (100) silicon substrates, using borazine and nitrogen as precursors. X-ray photoelectron spectroscopy, infrared spectroscopy, x-ray diffraction, nuclear reaction analysis and Rutherford backscattering spectroscopy were used to analyse the films. The results of quantitative XPS analysis indicate the formation of a thin surface layer (∼3 nm) of boron oxynitride, BNO0.3, over a bulk of nearly stoichiometric boron nitride, BN1.1. The presence of the hexagonal phase mixed with amorphous boron nitride was identified. Infrared and Rutherford backscattering spectroscopies combined with a liquid etching technique were used to determine the composition and structure across the film thickness. From these measurements we infer that the composition across the film is nearly constant but with a gradual transition from an amorphous structure close to the Si/BN1.1 interface to an hexagonal structure towards the outer layers. Thermal treatments of the boron nitride films up to a temperature of ∼1000°C in a nitrogen atmosphere resulted in a small decrease of both the B/N atomic concentration ratio and the refractive index of the film. The insulating characteristics of the boron nitride for application as an intermetal dielectric were also treated. The electrical conduction results can be interpreted in terms of a Schottky mechanism, which allows us to calculate the high-frequency dielectric constant, εr = 3.2.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 25 (1997), S. 677-682 
    ISSN: 0142-2421
    Keywords: silicon ; light irradiation ; surface tension ; transmission electron microscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The morphological differences between porous silicon formed in the dark or under illumination have been studied by means of gravimetric measurements, transmission electron microscopy, infrared spectroscopy and cyclic voltammetry. Photoetching has been found to give rise to a complex surface structure, due to the presence of narrower outer silicon fibres, which suffer a more severe cracking process upon drying. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
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  • 6
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Quantitative RBS and AES depth profiles of TiSi2 contacts deposited on GaAs by co-sputtering in a magnetron system have been performed. The bulk composition and thickness of the films were determined by RBS. AES showed that some oxygen was incorporated in the silicide layer during the deposition procedure. Comparing the depth profiles provided by both techniques, preferential sputtering effects have been studied. It is shown that silicon is preferentially sputtered as a consequence of its segregation to the surface. Sputter yields of the compound (YTiSi2 = 2.85 atoms ion-1) and of the individual components (YTic = 2.5 atoms ion-1 and YSic = 3.1 atoms ion-1) were also estimated for 3-keV Ar+ ions. Important interdiffusion effects appear to occur at annealing temperatures above 600°C. It is also observed that As has a higher mobility than Ga in TiSi2 when annealed at 800°C.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 12 (1988), S. 334-338 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Palladium silicide films were obtained after annealing thermally evaporated Pd layers on 〈111〉 p-type Si substrates. The silicide layers formed at different temperatures were characterized by Rutherford backscattering (RBS) and Auger electron spectroscopy (AES). A quantification of the AES depth profiles was made by comparing the profiles with the RBS results. The sputtering time scale was converted into a depth scale using the values of the sputtering yields calculated from the RBS thickness and the AES sputter times. The transformation of the measured Auger intensities into concentration allowed a quantitative study of preferential sputtering in Pd2Si, taking into account the composition given by RBS. Finally we estimated the depth resolution of the AES profiles by comparing the width of the interfaces obtained from both techniques.
    Additional Material: 3 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 22 (1994), S. 358-362 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Chemical composition and photoluminescence of free-standing porous silicon (PS) layers produced by anodization of p-Si in aqueous HF solutions at high current densities (Ja = 50-250 mA cm-2) are studied. It is shown that the PS layers are enriched in oxide phase, presumably due to silicic acid formation during the pore growth. Chemical composition of PS films produced at current densities about 100-150 mA cm-2 is non-uniform: internal faces of PS samples contain more silicon atoms than external. Their luminescent properties are also asymmetrical: the external face of the PS layer emits less light than the internal one. The samples grown at current densities above 200 mA cm-2 do not exhibit asymmetry of chemical composition and luminescence. The obtained results are considered based on existing models for PS luminescence and it is shown that the quantum confinement and siloxene-based models may fit the present data.
    Additional Material: 4 Ill.
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  • 9
    ISSN: 0142-2421
    Keywords: titanium silicide ; Schottky barrier ; silicidation ; rapid thermal annealing ; interface ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The silicidation process of titanium on silicon shows three distinct ranges depending on the treatment temperature. From 700°C up to 900°C, a stable and reproducible TiSi2 C54/Si structure is formed for all treatment conditions. At lower temperatures the silicidation process is not complete, and several silicide phases appear during the thermal treatment. On the other hand, the silicidation at high temperatures (T〉900°C) provokes changes in the TiSi2/Si structures. We have centred our interest in these two extreme ranges of temperature. The degree of silicidation has been established by Rutherford backscattering and grazing-incidence x-ray diffraction. It has been observed that TiSi and TiSi2 C54 are the only silicide phases present in the film at low temperatures. The distribution of phases has been determined by transmission electron microscopy. The high-resolution electron microscopy images indicate that the silicide/silicon interface is very flat, but the interface between the different phases of the silicide is not well defined. High-resolution electron microscopy and I-V measurements have been used to characterize the interface formed between the silicide and the silicon at high temperatures. At 1050°C the interface is flat in a scale of nanometres but it is rough in a scale micrometres. This roughening is not high enough to explain the decreasing of the Schottky barrier height. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
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