Introduction

Active research on the Surfaces and Interfaces Group beamlines has concentrated on many topics. In particular, strain, stress, growth and surface magnetism investigations high light the work performed in 2003

Intermixing and strain are two physical phenomena that play a major role in the electronic and optical properties of semiconductor nanostructures. A large research effort has been devoted to this topic over the last few years.

In what follows, the contribution of Schulli and collaborators show that by using grazing-incidence diffraction and anomalous scattering, the strain distribution and chemical composition of Ge dots deposited on Si substrates can be determined. The authors show that below the Ge islands there is a region of strained Si. Also, a detailed analysis reveals that the dots are mostly constituted of 80% of Ge and 20% of Si.

Similarly, Letoublon et al. investigated elongated islands of InAs (called "quantum sticks") embedded in InP using the same methods. The authors determined the strain within the islands (6%) and demonstrated some intermixing.

In metallic systems strain and stress is important in the context of surface magneto-elasticity. The contribution by Meyerheim et al. on Ni/W110 shows that the W substrate experiences an important re-arrangement induced by the deposited Ni atoms. The reconstruction of the W substrate is correlated with a giant compressive stress measured by optical methods.

The study of the fundamental aspects of film growth is another topic of the forthcoming contributions. The report by Fruchart et al. illustrates the use of the small angle scattering technique during the growth of Co islands on a reconstructed Au(111) substrate: this method allows the study of the islands growth and percolation. This information is relevant for the magnetic properties of such nanoislands. In a similar frame of ideas, Robach et al. investigated the growth of Ni on Pt(111) and of Pt on Ni(111). It turns out that in a Ni/Pt/Ni/Pt multilayer, the consecutive Ni layers are arranged in a unusual hcp stacking sequence which is believed to be the origin of the peculiar magnetic properties of these multilayers.

Unusual growth is also observed in an electrochemical system by Renner et al. who investigate the electrochemical corrosion of Cu3Au crystals. They observe the formation of a strained layer which grows with reverse packing sequence than that of the crystalline substrate. This acts as a protective layer against corrosion.

Finally, Torrelles et al. report on the determination of the structure of C60 adsorbed on the Ge(111) surface. It turns out that C60 accommodates onto the Ge substrate by making holes to sit on.

S. Ferrer