Behavior of F and O on the Si(100) surfaces dipped in aqueous solution of HF was examined by use of X-ray photoelectron spectroscopy (XPS). The F 1 s spectrum observed was separated into two Gaussian peaks with 685.6eV and 687.4eV binding energies, which are considered to correspond to Si-F and Si-F2 bonding respectively from the difference in the amount of negative charge of each F. Peak intensity of Si-F increased with increasing HF concentration of the solution. On the other hand, the variation of peak intensity of Si-F2 with HF concentration was small. In the F 1 s spectra from the Si(100) surfaces exposed to the atmosphere after dipping in aqueous solution of HF, peak intensity of Si-F decreased with increasing the exposing time, but that of Si-F2 hardly varied with the exposing time. These experimental results were explained in terms of the differences in the chemical bonding state between Si and F.
The areas of the peaks in the raw spectra were calculated by subtracting the backgrounds using a modified Tougaard method. The spectra used were obtained from the reference data in the Common Data Processing System by VAMAS. The results of the compositions were learned after many repetitions by the neurocomputing method. Then, the neuro-system clearly determined the compositions of the unlearned results.
We have calculated the electron inelastic mean free paths (IMFPs) in the range of 50∼2000 eV for 14 different organic compounds using the Penn algorithm. We report here mainly the calculated values of IMFPs for polyethylene and guanine, because their difference in density is the largest in this group of organic compounds. All the compounds had similar electron energy loss functions, and the computed IMFPs were similar in their magnitude and in the dependence on electron energy. The ratio of each calculated IMFP was 1.4 at 2000 eV ; this ratio is much smaller than those of metallic elements and inorganic compounds. Comparison of the calculated IMFPs for the organic compounds with the values obtained from our predictive IMFP formula TPP-2, which provides parameters in a modified Bethe formula, showed systematic differences of about 40%. These differences are attributed to the application of extrapolation of TPP-2, proposed on the basis of the calculated results of IMFPs for mainly high-density materials, to the low-density materials such as the organic compounds. We have, therefore, developed a modified empirical expression for one parameter in TPP-2 based on the IMFP data for the groups of elements, inorganic and organic compounds. Thus obtained modified equation, denoted TPP-2 M, gave satisfactory values of IMFPs for all materials in which IMFPs were calculated from experimental optical data using the Penn algorithm.
We have developed a DC magnetron sputtering apparatus for the coating of Nb films on the inner surfaces of a 500 MHz Cu cavity. Q0 values at 4.2 K by pipe cooling have been determined in order to optimize the various coating processes. The Nb films can be sputtered successively after sputter-cleaning the inner surfaces of the cavity by switching the polarity of the DC power supply operated at a constant power.