Results 1 - 10 of 2043
Results 1 - 10 of 2043. Search took: 0.028 seconds
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[en] Auger electron spectroscopy provides apparently simple procedures for studying the growth modes of vacuum-deposited ultrathin films. Mistakes of interpretation can occur, however, if certain factors are not carefully considered: (i) possible changes in the sticking probability at certain coverages; (ii) dissolution of the deposited material; (iii) anomalous variations in the parameters describing the emission and attenuation of the Auger electrons (possibly due to diffraction); (iv) the possibility of growth modes in which multiple layers form simultaneously (the nth layer starting before the (n-1)th layer is complete); (V) kinetic effects due to agglomeration; (vi) the effect of adsorbed impurities on the growth mode. These points are examined and a scheme for a set of procedures is proposed. (Auth.)
[en] Within a simple model the authors discuss the results of a calculation which contributes to the reliability of the use of the Auger technique as a quantitative tool. The adsorption of foreign species on a substrate is considered for three different cases: the submonolayer region, uniform thin film growth and island formation. It is shown that in all the cases it is possible to find a relation involving the peak-to-peak height ratios of the adsorbate Auger lines that gives the following information about the system: absolute coverage, thickness of the film and characteristics of the island growth respectively for the above cases. For the submonolayer region, only one Auger spectrum is necessary to evaluate the coverage. In the other cases it is also possible to establish whether the growth proceeds layer by layer or by island formation. (Auth.)
[en] Multilayered structures made of alternate carbon and tungsten films a few nanometers in thickness were analysed by Auger electron spectroscopy. The films were prepared by electron gun evaporation in a high vacuum. To obviate the lack of resolution of conventional depth profiling by sputter removal of very thin films, a special device was used which permitted the analysis to be performed during continuous deposition of the layers at room temperature. The amorphous carbon layers are free of contaminants; the shape of the carbon Auger lines reveals the occurrence of chemical bonding at both the C-W and the W-C interfaces. The tungsten layers contain oxygen at a concentration which varies with the deposition rate under a given pressure in the vacuum bell-jar. (Auth.)
[en] The application of a sufficiently high negative substrate bias, during the growth of tetrahedral amorphous carbon (ta-C), is usually associated with low sp3 bonding configuration and stressed films. However, in an effort to understand and utilize the higher pseudo thermo dynamical conditions during the film growth, at high negative substrate bias (- 300 V), reported here is a study on ta-C films grown under different hydrogen and nitrogen concentration. As grown ta-C films were studied under different negative substrate bias conditions. The variation of the sp3 content and sp3/sp2 ratio in the ta-C films exhibits a trend similar to those reported in literature, with a subtle variation in this report being the substrate bias voltage, which was observed to be around - 200 V, for obtaining the highest sp3 (80%) bonding and sp3/sp2 (3.95) ratio. The hydrogen and nitrogen incorporated ta-C films studied, at a bias of - 300 V, show an increase in sp3 (87-91%) bonding and sp3/sp2 (7-10) ratio in the range of studies reported. The inference is drawn on the basis of the set of data obtained from measurements carried out using X-ray photoelectron spectroscopy, X-ray induced Auger electron spectroscopy and Raman spectroscopy of as grown and hydrogen and nitrogen incorporated ta-C films deposited using an S bend filtered cathodic vacuum arc system. The study indicates the possibility of further tailoring ta-C film properties and also extending capabilities of the cathodic arc system for developing carbon based films for electronics and tribological applications
[en] Smoothing is a useful tool to improve the signal-to-noise ratio of spectroscopic data. This paper reports a new family of smoothing formulas, the Chebyshev filters, which are derived approaching the original data to a polynomial and using the mini-max principle, that is, keeping the maximum error down to a minimum, as fitting criterion. The properties of the filters are studied analyzing their associated transfer functions in the frequency domain. This leads us to the concept of spectral window and spectral window width as tool and parameter, respectively, to remove the high frequency noise components accompanying the experimental data. Also, simple criteria to choose the appropriate width of the spectral windows are put forward. The behaviour of the filters is easy to understand and the filters are fast and simple to use and to program. Finally the proposed smoothing algorithms have been tested using synthetic data as well as X-ray photoelectron spectra and optical absorption spectra
[en] In this paper we present experiments and simulations on the dissolution of Si into single crystalline Ge(111) substrates. The interface shift during the dissolution was tracked by X-ray Photoelectron Spectroscopy. It was obtained that the interface remained sharp and shifted according to anomalous kinetics similarly to our previous measurement in the Si/amorphous-Ge system. The interface shift, x, can be described by a power function of time x ∝ tkc with a kinetic exponent, kc, of 0.85 ± 0.1, larger than the one measured for the amorphous system (0.7 ± 0.1). Both exponents, however, are different from the kc = 0.5 Fickian (parabolic) value and it is interpreted as a nanoscale diffusional anomaly caused by the strong composition dependence of the diffusion coefficients.
[en] Concentration-depth profiles of sputter-deposited Si/Al multilayered specimens were determined by model fitting to measured data obtained by depth profiling, using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectrometry (TOF-SIMS). The model used for calculation of the concentration-depth profile accounts for the broadening ('smearing') upon experimental depth profiling owing to the effects of atomic mixing, preferential sputtering, surface roughness and information depth of either the Auger electrons (for AES depth profiling) or the photoelectrons (for XPS depth profiling) or the secondary ions (for SIMS depth profiling). The depth resolution for each technique was derived directly from the values determined for the fitting parameters in the model.
[en] In this paper, the results of XPS and AFM studies of the surface chemistry and morphology of In2O3 nanolayers obtained by rheotaxial growth and vacuum oxidation (RGVO) technology are presented. The ultrathin In films were deposited under UHV by thermal evaporation of indium pellets on the well defined Si substrate maintained at different temperatures. Optimal conditions to obtain the smallest grains and highest surface coverage have been determined, which was controlled by AFM, whereas the cleanness of deposited In nanolayers was controlled by XPS method. The ultrathin films of In2O3 (nm scale) were obtained in two ways, i.e. by oxidation of ultrathin films of In after their deposition, as well as by oxidation of In ultrathin films already during the deposition process. The XPS experiments showed that in both cases the obtained ultrathin films of In2O3 were almost stoichiometric. In turn, the AFM studies confirmed that only ultrathin films obtained during the simultaneous In deposition and oxidation exhibit almost flat surface morphology with average roughness at the level of about 0.85 nm.
[en] The condensation and early stages of gold growth on an Mo(110) surface was studied at various temperatures using the complementary techniques of Auger electron spectroscopy, low energy electron diffraction and thermal desorption spectrometry. The following growth mechanisms were found: a van der Merwe growth mode with no long-range order in the gold layers at 293 K and a Stranski-Krastanov mode favoured by a constrained (111) first layer formation at 933 K. (Auth.)