We have revisited the epitaxial growth modes of Fe on W(110) and Mo(110), and propose an overview or our contribution to the field. We show that the Stranski?Krastanov growth mode, acknowledged for a long time in these systems, is in fact characterized by a bimodal distribution of islands for a growth temperature in the range ~250?700??C. We observe firstly compact islands whose shape is determined by Wulff?Kaischev's theorem, and secondly thin and flat islands that display a preferred height, i.e.?are independent of nominal thickness and deposition procedures?(1.4?nm for Mo, and 5.5?nm for W on the average). We used this effect to fabricate self-organized arrays of nanometres-thick stripes by step decoration. Self-assembled nanoties are also obtained for nucleation of the flat islands on Mo at fairly high temperature, i.e.?~800??C. Finally, using interfacial layers and solid solutions we separate two effects on the preferred height, first that of the interfacial energy, and second that of the continuously varying lattice parameter of the growth surface.

https://hal.archives-ouvertes.fr/hal-00089174/document

Growth modes of Fe(110) revisited: a contribution of self-assembly to magnetic materials

Strain-induced magnetic anisotropies in Co films on Mo(110)

By means of first-principles calculations we predict the stability of silicene as buckled honeycomb lattice on passivated substrates of group-IV(111)1 × 1 surfaces. The weak van-der-Waals interaction between silicene and substrates does not destroy its linear bands forming Dirac cones at the Brillouin zone corners. Only very small fundamental gaps are opened around the Fermi level.

Silicene adsorbed on a hydrogen-passivated Si(111)1 × 1 surface (H: red, Si: blue).

(© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Silicene on hydrogen‐passivated Si(111) and Ge(111) substrates

Development of novel magnetic materials is of interest for fundamental studies and applications such as spintronics, permanent magnetics, and sensors. We report on the first experimental realization of single element ferromagnetism, since Fe, Co, and Ni, in metastable tetragonal Ru, which has been predicted. Body-centered tetragonal Ru phase is realized by use of strain via seed layer engineering. X-ray diffraction and electron microscopy confirm the epitaxial mechanism to obtain tetragonal phase Ru. We observed a saturation magnetization of 148 and 160 emu cm-3 at room temperature and 10 K, respectively. Control samples ensure the ferromagnetism we report on is from tetragonal Ru and not from magnetic contamination. The effect of thickness on the magnetic properties is also studied, and it is observed that increasing thickness results in strain relaxation, and thus diluting the magnetization. Anomalous Hall measurements are used to confirm its ferromagnetic behavior.

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Demonstration of Ru as the 4th ferromagnetic element at room temperature

The surface and interface structure as well as the electronic properties of thin epitaxial Fe 3 O 4 (111) films prepared by in situ oxidation of thin Fe(110) films grown on Al 2 O 3 (1120) substrates using a Mo(110) buffer layer were investigated by low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), transmission electron microscopy (TEM), and spin-polarized angle-resolved photoemission spectroscopy (SPARPES). The annealing of Fe(110) films at 700 °C in an O 2 atmosphere leads to the formation of epitaxial Fe 3 O 4 (111) films. Atomically resolved STM images of the Fe 3 O 4 (111) surface show a hexagonal symmetry with 6 A periodicity. Well-controlled interface properties at the Fe 3 O 4 (111)/Fe(110) and Fe(110)/Mo(110) interfaces were confirmed by TEM. A high spin polarization value of about -(60′5)% was found near the Fermi energy EF at room temperature by means of SPARPES with a photon energy of hv=21.2 eV. The electronic structure and spin polarization are compared to the corresponding values recently found on epitaxial Fe 3 O 4 (111) films grown on W(110) single-crystal substrates.

/pdf/preparation-structure-and-electronic-properties-of-fe3o4-69cejpgkk7.pdf

Preparation, structure, and electronic properties of Fe3O4 films on the Fe(110)/M(110)/Al2O3(1120) substrate

Characterization of epitaxial growth of Fe(110) on (11-20) sapphire substrates driven by Mo(110) seed layers

To optimize the structure±property relationship of layered systems exhibiting giant magnetoresistance (GMR) or tunneling magnetoresistance (TMR), there is a call for textured or epitaxial ferromagnetic layers deposited on semiconductor substrates. For high-performance GMR and TMR devices the interface properties (roughness, electronic interface states, spin polarization, phase purity, etc.) of the ferromagnetic/non-ferromagnetic metal layers (GMR) and ferromagnetic metal/insulator hybrid structures (TMR) play a crucial role. Currently, the astate-of-the-arto theoretical models for GMR and TMR systems are mainly developing calculations for epitaxial layers. Therefore the experimental investigation of epitaxial model systems becomes indispensable. In order to grow high-quality (textured or epitaxial) Co thin films on oxide-free Si substrates the possible advantages of Hpassivated Si(111) substrates have been explored. The latter can be prepared by aex situo wet-chemical processes and introduced easily into ultra high vacuum (UHV). The most reliable and reproducible results have been achieved on H-passivated Si(111) surfaces, although this crystal orientation may not yield continuous epitaxial growth of face-centered cubic (fcc) metal layers. In order to avoid silicide formation at the Co±Si interface, the influence of Ag buffer layers has been investigated. The influence of Ag deposition at elevated temperatures (ahoto Ag deposition at T = 550 C) on the formation of Si(111)-(2n+1)(2n+1) reconstructions will be discussed and compared with the results of the reconstruction formation on a H-Si(111) surface after H-desorption by thermal annealing. The influence of Ag deposited at a lower temperature (acoldo Ag deposition at T = 250 C) on the awet preparedo H-Si(111) surface has also been investigated and compared with the hot Ag deposition at 550 C on H-Si(111). In this paper, growth modes of Co and Ag on H-passivated Si(111) substrates will be presented and discussed with regard to possible applications for magnetoelectronic devices.

/pdf/the-growth-of-transition-metals-on-h-passivated-si-111-5ayb7z1px9.pdf

H. Kittur

Papers

Characterization of epitaxial growth of Fe(110) on (11-20) sapphire substrates driven by Mo(110) seed layers

The Growth of Transition Metals on H‐Passivated Si(111) Substrates