A. Di Cristoforo

Structural evolution of Fe-Al multilayers submitted to thermal annealing

In this paper, we present an experimental study on the structural evolution of B2 type FeAl multilayers submitted to thermal annealing. Multilayer samples have been obtained by evaporating 15 couples of 10 nm Fe and 14 nm Al layers on (100)-oriented Si wafers in an UHV chamber. After deposition, the samples have been heat treated at temperatures ranging from 375 to 775 K. Some samples were also annealed in air to promote the formation of a surface oxide layer. Different analytical techniques were used in order to achieve a complete characterisation of the deposited layers.

Dependence of the perpendicular anisotropy in Co/Au multilayers on the number of repetitions

The correlations between structure and magnetism in [Co(0.9 nm)/Au(5 nm)]×N multilayer films with different number of repetitions N=10, 30, and 50, have been studied by the combined use of complementary structural and magnetic techniques, such as x-ray reflectivity, x-ray diffraction, and transmission electron microscopy, alternating gradient force magnetometry, magnetic force microscopy and Brillouin light scattering. On increasing the value of N, an overall improvement of the multilayer quality is observed which corresponds to a change in the micromagnetic structure and to an enhancement of the perpendicular anisotropy. These effects have been attributed to a reduction of the magnetostatic energy associated with the formation of perpendicular magnetic domains in multilayers with increasing number of layers repetitions.

Intermixing at interfaces of Fe/W multilayers

The interface reactions in (1 nm Fe/x nm W) and (2 nm Fe/x nm W) multilayers (x = 1, 2, 5 and 7) with 5 or 10 periods in as-deposited state and under KrF laser irradiation with fluences, F= 0.05-0.25 J cm -2 and 1 or 10 pulses were studied by X-ray diffraction (XRD), grazing incidence (GI) XRD, X-ray reflectivity, GI X-ray diffuse scattering and cross-section transmission electron microscopy (XTEM). Structurally coherent layers along the [110] direction with bcc symmetry were found in as-deposited and irradiated samples. This coherency is affected by the lateral waviness of the interfaces. The layered structure persists up to F = 0.25 J cm -2 and 10 pulses. Under the laser treatment, both the interface roughness and mixing increase with increasing deposited energy and promoted bcc W grain growth is observed.

Crystallisation of perovskite PZT films on MgO substrates

Abstract Lead zirconate titanate (PZT) films deposited by sol–gel on MgO substrates have been studied by glancing angle X-ray diffraction (GAD) and scanning (SEM) and transmission (TEM) electron microscopy. To study the possibility of growing preferentially oriented films, two different compositions were considered: Pb(Zr0.52Ti0.48)O3 and Pb(Zr0.2Ti0.8)O3. Preliminary results suggest that a preferential orientation occurs depending on the film composition. In particular, a higher Ti content seems to favour the orientation along the [001] direction.

Lead zirconate titanate deposited on RuO2 by pulsed laser ablation

Abstract A systematic study of the phase distribution in PbZr0.52Ti0.48O3 films deposited, using a XeCl excimer laser, on two electrodes Si/RuO2 and Si/Ti/RuO2 has been carried out. In order to refine the growth parameters, the substrate temperature was changed in the range 600–700°C at two different values of the laser fluence, 3 and 6 J/cm2. The deposited films were characterized by grazing angle X-ray diffraction (GAD), scanning (SEM) and transmission (TEM) electron microscopy, energy dispersive spectroscopy (EDS) and measurements of the hysteresis loop by a modified Sawyer–Tower circuit. Results showed that at high fluence the perovskite phase decreases as the substrate temperature increases and that the Ti favours the nucleation of the perovskite.

Excimer laser-induced intermixing in irradiated Co/Ag nanometric bilayers and trilayers

Abstract Ag/Co bilayers and Co/Ag/Co trilayers were studied in order to extend our previous results on the excimer laser-induced grain boundary diffusion in Ag/Co layered structures, used in giant magnetoresistance devices. The e-beam deposited structures were processed by KrF excimer laser at the fluences F =0.1–0.25 J cm −2 with 1–1000 pulses. The temperature and depth of melting vs. time evolutions were computed for the first laser pulse. Samples were studied by X-ray reflectivity (XRR), X-ray diffraction (XRD), grazing incidence XRD, Rutherford backscattering spectrometry (RBS) and resistometry. The intermixing phenomena at the Ag/Co solid–solid, liquid–solid and liquid–liquid interfaces were quantitatively characterized. It was shown that in the immiscible Ag/Co combination of metals the interfaces could become sharper under laser processing, probably due to the back-diffusion effect.

Effect of composition and preparation conditions on the microstructure of lead zirconate titanate films

Abstract The crystallization behaviour of thin films of composition Pb 1.1 Zr x Ti 1 − x O 3 , where x = 0.75 and 0.25, prepared by a sol-gel route, have been studied using grazing angle X-ray diffraction and transmission electron microscopy. The X-ray diffraction was done at different incident angles and revealed different structures as the penetration into the film increased. Titanium-rich films were mainly perovskite with titanium oxide that may have formed within the film during its crystallization. The pyrochlore phase in the zirconium-rich film is more evident near the surface; this is also confirmed by microscopy of the film in cross section. In addition, an irregular distribution of the titanium, used as the adhesion layer was also seen on the micrographs. The electrical measurements evidence some correlation with the micro-structure observed.

Characterisation of ferroelectric thin films by X-ray diffraction and electron microscopy ☆

Abstract In this work an example of the application of glancing angle X-ray diffraction (GAD), scanning (SEM) and transmission (TEM) electron microscopy techniques, on the study of the phase distribution and microstructure of PbZr0.52Ti0.48O3 films deposited by two different methods, sol–gel and laser ablation, on different substrates, is reported. The investigations performed on the samples allowed us to obtain information on the phase distribution inside the films, on the diffusion processes occurred during the crystallisation treatments, on the presence of ferroelectric domains and on the structure of the columnar grains. The results showed that the electrical behaviour could be correlated to the microstructure of the films suggesting the best deposition conditions.