The growth and oxidation of vanadium ultra-thin films deposited on Fe(001) have been investigated by combining scanning tunneling microscopy and Auger electron spectroscopy. In the early stages of growth, vanadium develops a structure pseudomorphic to the Fe(001) substrate, nucleating one-layer-thick islands. At higher coverages, the growth proceeds nearly layer-by-layer, up to a thickness of about 5 atomic layers. Upon oxygen exposure, the vanadium film gets oxidized, while no signatures of the formation of iron oxides are detected in Auger spectra. As revealed by scanning tunneling microscopy images, the oxidation increases the surface roughness, suggesting the formation of an amorphous vanadium oxide layer.
We present a combined experimental and theoretical investigation of the magnetic behavior of ultra-thin Cr films grown on oxygen-passivated Fe(001)-p(1×1)O substrates. In all cases, oxygen floats on the metal/vacuum interface, where a monolayer-range oxide with peculiar electronic and structural characteristics is formed. Significant differences with previous experimental realizations of the Cr/Fe(001) heterostructure are thus introduced by the presence of oxygen. However, we show here that the magnetic behavior of our system is characterized by the same AF stacking at the Cr-Fe interface and by a layer-wise AF order in the Cr layer. In addition, we are able to circumvent the issue of chemical mixing at the Cr-Fe interface, characteristic of standard preparations.
We present a depth-resolved X-ray photoemission spectroscopy study of the Poly(9,9’-dioctylfluorene-cobenzothiadiazole):
Perylene tetracarboxylic diimide blend (briefly, F8BT:PDI), employed for the realization of the light
harvesting layer in organic photovoltaic devices. We address the problem of the vertical distribution of PDI molecules in
the blend, relevant for the optimization of the photo-generated charge collection in such devices. The depth resolution is
obtained by sputtering the organic layer with Ar+ ions. A thorough investigation of the effects of different sputtering
treatments on the F8BT:PDI film surface is presented. Changes in the stoichiometry of the organic layer, as well as the
cleavage of molecular bonds are detected, even after mild sputtering. In particular, we report about the formation of a
carbon-rich surface layer. Finally, a method is proposed for the calculation of the PDI concentration, which relies on the
detection of specific chemical markers and is robust against sputter-induced artifacts. As a case study, we evaluated the
PDI concentration in a 10 nm thick F8BT:PDI layer spin coated on indium tin oxide.
In this paper, we report on the characterization of the magnetic properties of layered Fe/CoO/Fe(001) magnetic structures
by means of Magneto-Optical Kerr Effect. Hysteresis loops were acquired on samples with variable CoO thickness, from
1 nm to 4 nm, and at different temperatures, from 30 K to room temperature. This characterization offers the opportunity
of exploiting the differences in the layer-dependent sensitivity of Kerr rotation and Kerr ellipticity in order to disentangle
the contribution of the different Fe layers in the hysteresis loops. Moreover, it allows us to give a detailed overview of
the magnetic behavior of the trilayers.