Structure, reactivity, electronic configuration and magnetism of samarium atomic layers deposited on Si(001) by molecular beam epitaxy

Abstract

The surface structure, interface reactivity, electron configuration and magnetic properties of Sm layers deposited on Si(001) at various temperatures are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and magneto-optical Kerr effect (MOKE). It is found that metal Sm is present on samples prepared at low temperature, with an interface layer containing SmSi 2 and Sm 4 Si 3. When samples are prepared at high temperature, much less metal Sm is found, with an increasing amount of SmSi 2. Room temperature ferromagnetism is observed for all prepared layers, with a decrease of the saturation magnetisation when samples are prepared at high temperature. It is found that ferromagnetism implies mostly a compound with approximate stoichiometry Sm 4 Si 3. Also, the decrease in the intensity of the XAS 2p 3/2 → 3d white lines with the corresponding increasing amount of SmSi 2 may be explained by assuming a higher occupancy of Sm 5d orbitals (5d 2 configuration), most probably due to hybridation effects.

Room Temperature Ferromagnetic Mn:Ge(001)

“…Previous quantitative analyses when using these factors have given reasonable results, applied to our setup [45,48,49,61]. Only for rare earths had these ASF to be slightly adjusted [22,23]. It may also be observed that the results obtained by using Ge 2p and Ge 3d do not deviate that much.…”

“…This is one of the few reports to our knowledge where a quite thick metal film is deposited onto a semiconductor and preserves its crystal structure and even its surface reconstruction. In the case of high temperature deposition of Fe on Si(001) (2 × 1)−(1 × 2) by using exactly the same setup, the LEED pattern vanishes starting with 1 nm of Fe thickness [ 20 , 21 ]; in the case of Sm/Si(001), a broad LEED pattern subsisted up to about 3.5 nm of Sm deposited [ 22 , 23 ]. A case closer to the present one was presented by Fe deposited in Ge(001) by keeping the substrate at high temperature (500 °C) [ 24 ], where the (1 × 1) LEED pattern of Ge(001) subsisted after 2 nm of Fe deposited; however, without providing also the (2 × 1)−(1 × 2) surface reconstruction of Ge(001).…”

A new green, ascorbic acid-assisted method for versatile synthesis of Au–graphene hybrids as efficient surface-enhanced Raman scattering platforms

“…As argued in ref. 62, each line from the simulations has its own associated inelastic background, expressed as an integral of the Voigt line; a vanishing value for this inelastic background coefficient indicates that the origin of these components is surface atoms.…”

Room Temperature Ferromagnetic, Anisotropic, Germanium Rich FeGe(001) Alloys

“…It may be surprising to attribute a higher binding energy component to Ge reacted with Fe, since usually semiconductors reacting with metals develop lower binding energy components [26,27]; however, for Fe–Ge, a similar binding energy (29.8 eV) was reported in [22]. The Fe(1):Ge(2) ratios represented in the next to the last column in Table 1 suggests the presence of surface compounds of approximate compositions ranging from FeGe 3 to Fe 3 Ge 5 , as indicated in the last column of Table 1.…”

“…Generally, few LEED patterns are obtained for metals deposited on semiconductors. In [ 10 ], Fe/Si(001) exhibited a LEED pattern only up to about 0.8 nm of Fe deposited, whereas in [ 26 , 27 ] Sm/Si(001) deposited at 300 °C showed a very diffuse LEED pattern for 3.2 nm of Sm deposited. Here, we obtained clear LEED patterns for the equivalent of 1.7 nm Fe deposited.…”