on the occasion of his 80th birthdayThe energy loss of protons in the energy region from 40 to 350 keV is measured for (110), (loo), and (1 11) planar channeling, for ( l l O > , (11 l}, (1 12> axial channeling, and for random directions in silicon. The investigations are carried out by means of the transmission experiment using silicon targets of several thicknesses. Stopping power values are derrved from the peak and the leading edge of energy spectra for channeled particles. Special procedures are applied to correct the obtained stopping power data with respect to the target thickness. In the case of leading edge the stopping power data depend strongly on the target thickness. It is shown that only the extrapolation to zero thickness leads to correct stopping power values for best channeled particles. It is found that the ratio of channeled to random stopping power shows a maximum in the energy region a t about 70 keV. Here the stopping power for channeling and random directions reach their largest value, too. I n der vorliegenden Arbeit werden die Energieverluste von Protonen im Energiebereich von

The evaporation and deposition process of Bis(acetylacetonato)platinurn(LI) fPt(acac)J was examined in a computerized microbalance system, which allows the measuring of the mass of evaporating precursor and depositing layer simultaneously. The investigations were carried out in an argon-atmosphere and an argonloxygen-atmosphere with pressure ranging from 250 Pa to 1000 Pa. The deposition kinetics were investigated in the temperature range between Tdep = 523 K and Tdep= 733 K. A strong dependence of the deposition rate on the pretreatment of the substrate was observed. Beginning the deposition on alumina with low deposition temperatures Tdep an activation energy of 204 + 9 Mlmol was found. On platinum precoated substrates we observed higher deposition rates and lower values for the activation energy, if the precoating was carried out at temperature T w > Tdcp. At long deposition tirnes with Tdep= const. the deposition rates on precoated substrates decreased to the values obtained without precoating at higher temperatures. This effect has not been clarified. In argon-atmosphere platinum layers containing carbon were deposited. Increasing the deposition temperature caused increased carbon contamination. The carbon can be removed by oxidation in air after the deposition. Platinum coatings without carbon contamination were obtained by adding oxygen during the deposition process.

The Chemical Vapor Deposition of boron nitride from BB'BU-Trichloroborazine was investigated in a microbalance equipment with a hot wall reactor. It was possible to monitor the evaporating and depositing masses simultaneously, so that the kinetics of the CVD-process could be measured in detail. The evaporation rate was studied in the temperature range between 285 and 330 K. The activation energy of the evaporation was determined to be 65 & 2 Mlmole. The deposition process was investigated at temperatures between 973 and 1233 K in an argon atmosphere at total pressures between 250 and 2000 Pa. The deposition of boron nitride on silicon could be described by a Langmuir reaction type. A gas phase decomposition of BB'B-Trichloroborazine was observed, so that the concentration at the substrate was dependent on the residence time of the precursor in the hot zone of the reactor. The deposited layers were colorless and amorphous and had the correct 111 stoichiometry between boron and nitrogen (WDX-Analysis). The layers contained less than 1 % of chlorine. SiC-Tyranno-fiber fabrics were coated homogeneously with BN-layers of 200-300 nm thickness. A tensile strength decrease of approximately 15 % was observed for the coated fibers. Oxidation experiments showed that the layers were oxidized at temperatures above 873 K in an Arl02-atmosphere leading to a brittle behavior of the fibers.

The adsorption of a nonionic amphiphile at the solutiordair interface has been studied by surface secondharmonic generation. The bulk phase transition of micellization was observed by monitoring the surfacereflected nonlinear signal. The concentration dependence ofthe second-harmonic signal could be described in terms of a Langmuir isotherm allowing the determination ofthe free energy of adsorption of the nonionic molecules at the surface. A comparison with experimental data obtained from surface tension measurements suggests a depth-dependent distribution of the surfactant molecules rather than a monolayer-type surface coverage. IntroductionIn aqueous solutions ofnonionic amphiphiles, the critical micelle concentration (cmc) is, in general, determined by measuring the concentration dependence of the interfacial tension (a) against air. Upon plotting u vs log x , with x denoting the mole fraction of the amphiphile in the bulk phase, the break of slope in the aAogx curve identifies the onset of micellization. As further information, the experiment yields the concentration dependence of the

Experimental results are reported regarding the multiple scattering of lithium ions with energies from 10 to 50 keV in carbon, aluminium, silicon, vanadium, chromium, iron, cobalt, and germanium. The targets consisted of thin self-supporting foils 150 to 700 A thick, The results of the scattering measurements agree satisfactorily with Meyer's theory of multiple scattering with regard t o the dependence on the energy of the ions, foil thickness, and the form of the scattering distribution.In der vorliegenden Arbeit werden experimentelle Ergebnisse zur Vielfachstreuung von Lithium-Ionen mit Energien von 10 bis 50 keV in Kohlenstoff, Aluminium, Silizium. Vanadium, Chrom, Eisen, Kobalt und Germaniummitgeteilt. Die Targets bestanden aus diinnen freitragenden Folien der Dicke 150 bis 700 A. Die Ergebnisse der Streumessungen zeigen bezuglich der Abhangigkeit von der Energie der Ionen, der Foliendicke und der Form der Streuverteilung befriedigende Ubereinstimmung mit der Theorie der Vielfachstreuung von Meyer.