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A set of experimental very low-energy electron diffraction VLEED intensities on Cu(001) for angles of incidence of 35°, 40°, 50°, 60°, 70° and 80° in the (11) azimuth obtained by Dietz, McRae and Campbell has been analyzed using a surface-barrier model which allows for the angle and energy dependence of both the saturation from the image form and the height of the barrier potential. All three parameters of the potential form were allowed to vary independently. It is found that a fit between experiment and theory of the energy position of all the features (minima and maxima) in the entire data set to ≤ 0.07 eV can be obtained with the image-plane origin at z[sub 0] = -1.70 ± 0.05 Å from the center of the first row of atoms with a barrier height U[sub 0] increasing in energy from 11.6 eV with respect to the muffin-tin zero at 35° incidence to 13.1 eV at 80°. The saturation from image form is found to show no trend in variation with respect to the energy or angle of approach of the electron to the barrier and has a value of U[sub D] = 5.4 ± 1.0 eV with respect to the vacuum level at the jellium discontinuity. The value of z[sub 0] and barrier form found here differs from that of previous work of others and the analysis uses the largest VLEED data set to date. [ABSTRACT FROM AUTHOR]

Nanocrystalline formation in the amorphous ribbons, Fe[sub 79]B[sub 15]S[sub 15] and Fe[sub 78]B[sub 13]Si[sub 9], resuiting from annealing the ribbons at temperatures below their crystalline temperature is followed by Mossbauer spectroscopy. It is seen that in the B-rich Fe[sub 78]B[sub 16]S[sub 15] ribbons, the crystallization is a two stage process: amorphous → α-Fe(Si) nanocrystalline formation → (α-Fe, Fe[sub 2]B) nanocrystalline formation while the crystallization in the B-poor Fe[sub 78]B[sub 13]Si[sub 9] ribbons is a three stage process: amorphous → Fe[sub 3]B nanocrystalline formation → α-Fe(Si) nanocrystalline formation → (α-Fe, Fe[sub 2]B) nanocrystalline formation. These direct observation confirms the inferred formation of nanocrystallites obtained from magnetization measurements of similar type Fe-Si-B amorphous alloys. Our study also indicated that the α-Fe(Si) nanocrystallites survives at the higher temperatures. [ABSTRACT FROM AUTHOR]