LEED and DFT investigation on the (2×2)-S overlayer on Co(0001)

Lahtinen, Jouko; Kantola, Panu; Jaatinen, Sampsa; Habermehl-Cwirzen, Karin; Salo, Petri; Vuorinen, Johannes; Lindroos, M.; Pussi, Katariina; Seitsonen, Ari P.

doi:10.1016/j.susc.2005.09.042

Cited by 22 publications

(10 citation statements)

References 27 publications

(30 reference statements)

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“…At low Co coverage, when part of the Au(111) surface is uncovered, we could observe locally some hexagonal molecular packing on Co with molecular orientations compatible with either a ( 3 3) × or a (2 2) × structure (cf inset of figure 2(b)). It is worth noting that according to first principles calculations for methanethiolate on Co(0001) [21], the (2 2) × and ( 3 3) × structures lie very close in energy, and for the case of sulfur adsorption on Co(0001), the (2 2) × superstructure has been experimentally observed with LEED ( [33]) and theoretically predicted to be the most stable structure [34]. In order to complete the characterization of the SAMs on the Co layers, we have performed AES.…”

Section: Resultsmentioning

confidence: 84%

Change of cobalt magnetic anisotropy and spin polarization with alkanethiolates self-assembled monolayers

et al. 2015

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We demonstrate that the deposition of a self-assembled monolayer of alkanethiolates on a 1 nm thick cobalt ultrathin film grown on Au(111) induces a spin reorientation transition from in-plane to outof-plane magnetization. Using ab initio calculations, we show that a methanethiolate layer changes slightly both the magnetocrystalline and shape anisotropy, both effects almost cancelling each other out for a 1 nm Co film. Finally, the change in hysteresis cycles upon alkanethiolate adsorption could be assigned to a molecular-induced roughening of the Co layer, as shown by STM. In addition, we calculate how a methanethiolate layer modifies the spin density of states of the Co layer and we show that the spin polarization at the Fermi level through the organic layer is reversed as compared to the uncovered Co. These results give new theoretical and experimental insights for the use of thiol-based self-assembled monolayers in spintronic devices.

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Section: Resultsmentioning

confidence: 84%

Change of cobalt magnetic anisotropy and spin polarization with alkanethiolates self-assembled monolayers

et al. 2015

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“…Experimental studies of interaction of H 2 S with close-packed transition and noble metal surfaces (Ag(1 1 1) [7], Au(1 1 1) [8], Co(0 0 0 1) [9], Cu(1 1 1) [10] and Pt(1 1 1) [11]) as well as with the corresponding open surfaces (Ag(1 0 0) [12,13], Au(1 0 0), Au(1 1 0) [14][15][16], Cu(1 0 0) [17], Mo(1 0 0) [18], Ni(1 0 0) [19][20][21], Ni(1 1 0) [22], Pd(1 0 0) [23], Rh(1 0 0) [24], Ru(1 1 0) [25], W(1 0 0) [26]) were reported. A variety of techniques such as low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), X-ray photoemission spectroscopy (XPS), normal incidence X-ray standing wave (NIXSW) analysis, temperature program desorption (TPD), high-resolution electron energy loss spectroscopy (HREELS) and Auger electron spectroscopy (AES) were utilized.…”

Section: Introductionmentioning

confidence: 99%

“…These efforts have included work on close-packed surfaces of transition (Co(0 0 0 1) [9], Ru(0 0 0 1) [27][28][29][30], Ir(1 1 1) [31], Ni(1 1 1) [32][33][34][35], Pd(1 1 1) [36][37][38][39][40], Pt(1 1 1) [41][42][43][44], Rh(1 1 1) [45][46][47]) and noble metals (Ag(1 1 1) [12,48,49], Au(1 1 1) [50][51][52], Cu(1 1 1) [53][54][55]). The formation of ( p 3 Â p 3) R30°structure on the (1 1 1) surfaces was frequently observed while the (2 Â 2) structure was commonly reported on the (0 0 0 1) face.…”

Section: Introductionmentioning

confidence: 99%

First-principles studies of H2S adsorption and dissociation on metal surfaces

2008

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Exposure of Pd-based hydrogen purification membranes to H,S. a common contaminant in coal gasification streams, can cause membrane performance to deteriorate, either by deactivating surface sites required for dissociative H, adsorption or by forming a low-permeability sulfide scale. In this work. the composition, structure, and catalytic activity of Pd4S, a surface scale commonly observed in Pd-membrane separation of hydrogen from sulfur-containing gas streams, were examined using a combination of experimental characterization and density functional theory (DFT) calculations. A Pd,S sample was prepared by exposing a 100 f1m Pd foil to H2S at 908 K. Both X-ray photoemission depth profiling and low energy ion scattering spectroscopic (LEISS) analysis reveal slight sulfur-enrichment of the top surface of the sample. This view is consistent with the predictions of DFT atomistic thermodynamic calculations. which identified S-terminated Pd,S surfaces as energetically favored over corresponding Pd-terminated surfaces. Activation barriers for H2 dissociation on the Pd,S surfaces were calculated. Although barriers are higher than on Pd(lll). transition state theory analysis identified reaction pathways on the S-terminated surfaces for which hydrogen dissociation rates are high enough to sustain the separation process at conditions relevant to gasification applications.

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“…But, even at the absolute temperature of T = 0 K, the quantum vibrations of the foreign atom would make the uncertainty of its position comparable with the characteristic dimension of its K shell. Using the Debey approximate treatment of the effect of thermal vibrations [29] and an estimated value of the Debey temperature of the foreign atom, being 300 K [44], one can calculate that for T = 0 K, the one-dimensional thermal vibration amplitude of the foreign atom is 6.2 pm. On the other hand, the characteristic dimension of the K shell of the foreign atom is 5.1 pm, and the characteristic dimensions of its L and M shells are about 25 and 100 pm, respectively [45].…”

Section: Rainbow Subatomic Microscopymentioning

confidence: 99%

Superfocusing of channeled protons and subatomic measurement resolution

et al. 2012

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In this work we analyze the superfocusing of protons channeled in a 100 Si thin crystal using the theory of crystal rainbows. The initial proton energy is 68 MeV and the proton beam incident angle is increased gradually from zero up to 30% of the critical angle for proton channeling. The reduced crystal thickness is varied around 0.250, the corresponding crystal thickness being 481.8 nm. The spatial distributions of channeled protons, obtained by the numerical solution of the proton equations of motion in the transverse position plane and a Monte Carlo computer simulation code, are explored as functions of the beam incident angle and reduced crystal thickness. They are analyzed via the corresponding mappings of the impact parameter plane to the transverse position plane, which are characterized by the rainbow effect. The performed analysis shows that it is possible to focus the beam within the region of the radius considerably below the Bohr radius. The obtained results provide the theoretical basis for the possible development of a measurement technique with the picometer resolution-the rainbow subatomic microscopy.

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LEED and DFT investigation on the (2×2)-S overlayer on Co(0001)

Cited by 22 publications

References 27 publications

Change of cobalt magnetic anisotropy and spin polarization with alkanethiolates self-assembled monolayers

Change of cobalt magnetic anisotropy and spin polarization with alkanethiolates self-assembled monolayers

First-principles studies of H2S adsorption and dissociation on metal surfaces

Superfocusing of channeled protons and subatomic measurement resolution

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