H. Jenniches

Comparison of pulsed laser deposition and thermal deposition: Improved layer‐by‐layer growth of Fe/Cu(111)

In the search for a correlation between the magnetism and the microstructure of ultrathin films, straightforward layer‐by‐layer growth is desirable. The thermal deposition of Fe onto Cu(111), however, does not result in this growth mode. In this letter, we compare the initial growth of Fe on Cu(111) prepared by pulsed laser deposition (PLD) with thermally deposited Fe/Cu(111) using scanning tunneling microscopy (STM). In PLD, from the beginning there is two‐dimensional nucleation and growth, in contrast to the initial bilayer nucleation and growth found for thermal deposition. Therefore, it is shown by STM that PLD grown films exhibit greatly improved layer‐by‐layer growth. The different experimental results are interpreted in terms of the very high deposition rate during PLD.

Growth, morphology, and crystalline structure of ultrathin Fe films on Cu3Au(100)

The growth mode, morphology, and crystalline structure of Fe films on Cu 3 Au(100) are studied for diVerent growth temperatures (300 and 160 K ), using in situ scanning tunneling microscopy and low energy electron diVraction. Multilayer growth is found to be predominant for both growth temperatures. Only in films of 3‐4 monolayers (ML) grown at 300 K is a mixed mode of layer-bylayer growth and island growth observed. An fcc-to-bcc structural transformation, accompanied by a distinct change in the surface topography, starts at about 3.5 ML and 5.5 ML for the growth temperatures of 300 and 160 K, respectively. For both growth temperatures bcc-like Fe in Fe/Cu 3 Au(100) assumes, most likely through a Bain path, a surface plane with the (100) rather than the (110) orientation found in the Fe/Cu(100) system. Both the surface morphology and the onset thickness of the fcc‐bcc structural transformation are shown to be strongly aVected by the growth temperature.

Strain-driven formation of two-dimensional holes on Cu(111) after the deposition of Fe

Abstract The formation and growth of one-monolayer-deep holes after the deposition of Fe on a Cu(111) vicinal surface at 300 K are studied by scanning tunneling microscopy (STM). At low Fe coverages; hole formation starts between separate Fe islands grown at step edges. As hole formation is accompanied by the creation of edge energy, it is assumed that the tensile stress field between the adjacent Fe islands provides the driving force for this process. At higher Fe coverages, another hole formation process is induced by the strain field at Fe wires, resulting in a step-up diffusion. Both hole-creating processes can be suppressed by depositing Fe at lower temperatures and subsequently sealing Cu steps and Fe wires by depositing Au.

ON THE FABRICATION OF STACKED MONOLAYERS OF FE/CU ON CU(100) BY PULSED LASER DEPOSITION

We report on the artificial fabrication of stacked monolayers of Fe/Cu on Cu(100) by pulsed laser deposition at 300 K employing reflection high energy electron diffraction (RHEED). In contrast to the thermally deposited films, an improved two dimensional growth of the Fe and Cu layers has been achieved by virtue of the dynamics of the pulsed laser deposition technique. The observed RHEED oscillations for each Fe and Cu layer and their growth mode as studied by scanning tunnelling microscopy indicate layer-by-layer growth. The magnetic properties studied by magneto-optical Kerr effect measurements show that the easy axis of magnetization is in plane with no specific anisotropy observed in the plane. Ferromagnetic response was absent for thicknesses less than 2 ML in total within the measured temperature range down to 100 K. The Curie temperature increases from 225 K for a trilayer Fe/Cu/Fe to 400 K for a total layer thickness of 10 ML.

Comparison of magnetism and morphology of ultrathin Fe films on Cu(100) and Cu3Au(100)

In order to obtain a deeper insight into the inter-relation of magnetism and morphology we compare the properties of Fe films on Cu(100) and Cu 3 Au(100) grown at different temperatures, using the magneto-optical Kerr effect and scanning tunnelling microscopy. In Fe films on Cu 3 Au(100) for both room- and low-temperature growth (RT and LT growth) neither an antiferromagnetic phase nor a good layer-by-layer growth, as found for RT growth in Fe/Cu(100), was observed. The critical thickness at which the spin reorientation transition from perpendicular to in-plane easy axis starts, is found to be 3.5 ML for RT-grown Fe/Cu 3 Au(100) as compared with 5.5 ML for the LT-grown films on both substrates.

Changes of morphology, structure, and magnetism of Fe on stepped Cu(111)

We have studied the morphology, structure and magnetism of Fe films thermally deposited on stepped Cu(111) by scanning tunnelling microscopy (STM), low energy electron diffraction (LEED) and magneto-optical Kerr effect (MOKE). At room temperature, in the submonolayer range Fe films grow as quasi one-dimensional stripes along the upper step edges due to a strong decoration effect. Between 1.4 and 1.8 monolayer coverage the stripes percolate and become two-dimensional films. Between 2.3 and 2.7 monolayer coverage the films undergo a structural transition from fcc(111) to bcc[110] with Kurdjumov-Sachs orientation. In the fcc range the films have a low net magnetic moment, and a perpendicular easy magnetization axis. The magnetization switches to an in-plane high-moment phase correlated with the fcc to bcc structural transformation.