M Petty

Evidence of roughness distributions and interface smoothing in Co/Cu multilayers deposited under energetic particle bombardment

The interfacial structure of Co/Cu multilayers deposited under energetic particle bombardment is investigated using x-ray reflectivity. The energetic bombardment is varied by controlling the ion bombardment of the growing film. Specially modified unbalanced magnetron sources are used in collaboration with bias sputtering techniques in order to independently vary both the ion flux and average ion energy of the bombardment. Quantitative analysis of the specular reflected intensity reveals the existence of variations of the interface roughness in multilayers deposited with high applied negative biases of 200 V, such that the interfaces become smoother towards the free surface. A maximum smoothing effect is observed for films deposited with the highest available levels of ion flux. A static interface roughness is observed when applied biases of are applied.

Experimental determination of the partial density of states for the binary alloys and

The valence band electronic structure of the intermetallic compounds and has been investigated by means of synchrotron radiation ultraviolet photoemission. The spectra exhibit band structure extending to approximately 8 eV below the Fermi level for each alloy. Utilizing the Cooper minimum in the Pt 5d photoionization cross-section, the partial densities of states have been empirically determined. The results indicate that the d bands of the constituent metals completely overlap. The V 3d states contribute most strongly to the valence band immediately below the Fermi level. In contrast, the highest occupied density of states for the Mn 3d band lies approximately 2.6 eV below the Fermi level. For , 3p to 3d resonant photoemission confirms the results obtained at the Pt 5d Cooper minimum. However, no clear evidence for a corresponding V 3p to 3d resonance was observed in . This may indicate that the V d states in are significantly less localized than the Mn d states in . The empirical results for each alloy have been compared with theoretical calculations from the literature and provide good agreement in each case.

SIMPLE METHOD FOR THE CONTROL OF SUBSTRATE ION FLUXES USING AN UNBALANCED MAGNETRON

Substrate ion fluxes from unbalanced magnetron sources are generally controlled by the use of additional magnetic fields. These methods are not always suitable for differentially controlling the ionic flux from multiple sources. We report here a simple method suitable for attaining such control that can be easily adapted to most unbalanced magnetron systems. The flux leakage from an unbalanced magnetron is controlled by the use of a mild steel keeper with a detachable mild steel annulus. The annulus redirects the unbalanced field lines through the keeper to the rear poles of the magnetron. The flux leakage is thus controlled by varying the thickness of the annulus. Ion saturation currents measured at the substrate, with and without a 0.9 mm thick mild steel annulus, were found to differ by a factor of approximately 3 at an argon partial pressure of 1 mTorr. Furthermore we demonstrate that the changes in ion current density are achieved without alteration to the magnetron operating parameters.

Microstructural modification in Co/Cu multilayers prepared by low energy ion-assisted deposition

Abstract The microstructure of Co/Cu multilayers deposited by low energy ion-assisted deposition was investigated. The samples studied were grown by unbalanced magnetron sputtering with and without an applied d.c. substrate bias of −50 V. Specular and off-specular X-ray reflectivity measurements were performed on the samples and revealed the presence of roughness at the interfaces that was partially correlated throughout the film. The effect of applying a −50 V bias was to suppress the correlation of the lower frequency roughness and to slightly reduce the bilayer period of the multilayer. The differences between the samples are discussed in terms of possible ion bombardment induced smoothing of the layers and densification of the microstructure.

Atomic force microscopy investigation of polysilicon films before and after SIMS analysis: the effects of sample rotation

Differences have been found in the depth resolution of dynamic SIMS profiles from polysilicon films on silicon carried out with and without sample rotation. Corresponding differences in the surface topography have been observed using atomic force microscopy. Both amorphous and polycrystalline silicon films implanted with fluorine and arsenic and subjected to rapid thermal annealing were examined. For the polycrystalline film, conventional SIMS analysis led to a significantly roughened crater, with a somewhat lesser roughening effect in the case of the rotational SIMS. The crater in the amorphous film showed slight roughening in the conventional analysis mode whereas with rotation the crater base appears to preserve the initial topography of the film.

A study of the Heusler alloy using ultraviolet photoemission spectroscopy

Ultraviolet photoemission spectroscopy has been employed to provide information on the valence band of the Heusler alloy. The contribution of the d bands of Mn and Cu to the density of states has been investigated by means of 3p to 3d resonant enhancement. The valence band extends to 6 eV below the Fermi level, with a main peak at a binding energy of 3.2 eV and a shoulder extending to the Fermi edge. Resonant photoemission indicates that the Mn 3d character extends across the full width of the band. An experimental photoemission spectrum obtained at a photon energy of 40 eV has been compared with a calculated spectrum derived from a theoretical band structure. The main difference occurs in the region 1 - 2 eV below the Fermi level. The calculated spectrum exhibits a peak at a binding energy of 1.5 eV, comprising contributions from both the Cu and Mn 3d bands. There is no evidence of a similar feature in the experimental spectrum.

The experimental density of states of Pd 4d and Ti 3d in the intermetallic compound

Photoemission measurements have been made of the intermetallic compound utilizing synchrotron radiation in the energy range 40 - 180 eV. The valence band extends to a binding energy of 7 eV. Measurements made at the Cooper minimum for Pd 4d indicate that the highest density of states for Ti 3d is at the Fermi edge and that it decreases towards higher energy. Using this density of states and correcting for the photoemission cross-sections with energy, it has been possible to determine the density of states for Pd 4d which also contributes to the Fermi level. Resonance photoemission measurements are consistent with this conclusion and also indicate that the Pd 4d band is not completely full.

Ultraviolet photoemission studies of the Pd2TiAl Heusler alloy

Abstract The valence band of the ferromagnetic Heusler alloy Pd 2 TiAl has been investigated using synchrotron radiation ultraviolet photoemission spectroscopy. By use of the Cooper minimum for palladium it was found that the Fermi level of the material is dominated by titanium 3d electrons.

A photoemission investigation of the valence band electronic structure of and

The valence bands of the intermetallic compounds and have been investigated by ultraviolet photoemission utilizing synchrotron radiation. The valence bands of both alloys have a width of 7 - 8 eV with a prominent peak at a binding energy of 2.6 eV and a shoulder extending to the Fermi edge. Measurements obtained at the Pd 4d Cooper minimum and at the Ti 3p threshold indicate that the feature at 2.6 eV is largely composed of contributions from Pd 4d states, whereas the Ti 3d states contribute most strongly immediately below the Fermi level. Experimental photoemission spectra show good agreement with theoretical calculations.

Amorphous alloys as secondary standards for electron spin polarimetry

The surface magnetism of as-cast and field annealed amorphous in ribbon form has been studied by spin-polarized secondary electron spectroscopy, by recording energy-resolved spin asymmetry hysteresis loops and by scanning electron microscopy with polarization analysis. Large lateral variations in surface magnetization have been detected, indicating that , in particular, and ferromagnetic melt-spun ribbons, in general, are not suitable as standard sources of polarized electrons. Deposition of an iron film onto the did not result in a more uniform surface but rather served to emphasize the substrate magnetic structure. Thus utilization of ferromagnetic melt-spun amorphous alloys as substrates for the growth of thin magnetic films should be undertaken with caution.