on the occasion of his 75th birthday High resolution backscattering measurements are performed in the (110)-plane of silicon single crystals with 80 to 300 keV protons. The observed oscillatory spectra me in good agreement with analytical calculations. The first two maxima of the spectra are used for the determination of the ratio between planar and random stopping power y for quasi-channelled protons. This ratio turns out to be energy-dependent and larger than unity. The half-wavelengthsj1/2 of the oscillations are calculated on the basis of the Fokker-Planck equation. Conclusions for the ion-atom potential are deduced.Hochauflosende Riickstreumessongen werden in der (1 10)-Ebene von Siliziumeinkristallen mit 80 bis 300 keV Protonen durchgefiihrt. Die beobachteten oszillierenden Spektren stimmen gut mit den analytischen Rechnungen iiberein. Die beiden ersten Maxima der Spektren werden zur Bestimmung des Verhiiltnisses y zwischen planarem und random-Energieverlust fur quasi-kanalisiorte Protonen benutzt. Dieses Verhlltnis ist energieabhangig und grol3er a1s eins. Die halben Wellenlangen der Oszillationen werden mit Hilfe der Fokker-Planck-Gleichung berechnet. SchluBfolgerungen fur das Ion-Atom-Wechselwirkungspotential werden gezogen.

Short Note we present transmission and backscattering measurements for the determination of the proton stopping power in silicon. The significant differenc e s between an amorphous and a crystalline target a r e discussed,The experimental set-up was described in /2/. For the transmission experiments thin amorphous Si foils of various thicknesses from 47 nm to 250 nm were used. The layer thicknesses were determined by an analysis of backscattering signals what is possible without knowledge of the stopping power. The energy of the protons before and after passing the foils was measured by an electrostatic analyzer with an accuracy better than 0.5 %. Fig. 1 shows the energy loss of the protons AE in dependence on the target thickness Ax for several primary energies E In the used interval a linear function between AE and Ax exists.From the slope of the functions the stopping power can be determined. 0' Rutherford backscattering (PBS) experiments were carried out with amorphous and crystalline (Ill)-oriented Si targets. The crystalline specimens were rotated around an angle of 120 O, 15 for obtaining a random value of the RBS signal. The backscattering yield H for the primary ener 0 away from the -aXiS gy E w a s measured for several emerging 0 t 3R 20 L 41 10 Fig. 1, The dependence of energy loss on the layer thickness for various primary energies in the transmission experiment; + 50 keV, A 70keV, 0 150keV, o 300keV 0 SR 100 I . ZRR 2.50 dx (nm) -1) Invalidenstr. 42, DDR-1040 Berlin, DDR.

Backscattering spectra are measured in channeling-, blocking-, and double-aligned-arrangement. From these data it is possible to determine damage and dechanneling profiles. The method is applied to damaged silicon monocrystals. Riickstreuspektren werden in channeling-, blocking-und double-alignment-Anordnung gemessen. Aus diesen MeDwerten kann man Dekanalisierungs-und Strahlenschadenprofile bestimmen. DieMethode wird auf strahlengeschiidigtes Silizium angewendet.