Epitaxial CrO 2 (100) island films have been grown on TiO 2 (100) substrates by a chemical-vapor deposition technique. Well-controlled surface and interface properties of the CrO 2 (100) films were confirmed by scanning tunneling microscopy and transmission electron microscopy, respectively. Spin-and angle-resolved photoemission spectroscopy at room temperature revealed an energy gap of about 2 eV below Fermi level E F for spin-down electrons and a spin polarization of about ϩ95% at E F . After extended sputtering, the spin polarization can be recovered from about ϩ10% up to ϩ85% upon annealing. 1-3,7,10-13The HMF nature of CrO 2 has been predicted on the basis of the local-spin-density approximation ͑LSDA͒ to the density-functional theory.1,3 Only recently, spin polarization values of over 90% near E F were found for CrO 2 at 1.8 K using superconducting point contact spectroscopy, 7,11-13 although values of 95% had been obtained earlier by spinpolarized photoemission at 293 K for binding energies of about 2 eV below E F .14 In this letter, we present a study of structural properties and of the spin-dependent electronic structure of epitaxial CrO 2 (100) island films prepared on isostructural TiO 2 (100) substrates by a chemical-vapor deposition ͑CVD͒ technique. 15 The CrO 2 (100) surface shows in scanning tunneling microscopy ͑STM͒ the growth of large elongated rectangular-like epitaxial islands with a preferential growth direction along the in-plane ͓001͔ axis. A sharp CrO 2 (100)/TiO 2 (100) interface without intermixing and a good crystalline quality of CrO 2 (100) were found by transmission electron microscopy ͑TEM͒. The spin-dependent electronic structure of the CrO 2 (100) films has been investigated at 293 K by means of spin-and angle-resolved photoemission spectroscopy ͑PES͒. Below the Fermi level E F an energy gap of about 2 eV was observed for spin-down electrons, and thus a spin polarization of up to ϩ95% at E F was found at 293 K. Both the magnitude of the spin-down gap and the value of the spin polarization are in good agreement with theoretical band-structure calculations, which predict only majority spin electrons at E F .1,3 Sputtering of the asprepared surface up to 210 s increases the spin polarization from ϩ80% to ϩ95%. Continued sputtering up to 750 s results in about ϩ10% spin polarization, which can be increased again up to ϩ85% by annealing for 12 h at 150°C in ultrahigh vacuum ͑UHV͒.The CrO 2 (100) films were prepared by a CVD technique proposed by Ishibashi.15 As substrates isostructural TiO 2 (100) ͑rutile; aϭ4.592 Å; cϭ2.959 Å; space group: P4 2 /mnm͒ has been used. CrO 3 is decomposed at a temperature of 260°C within a two-zone tube furnace. A wellcontrolled oxygen flow ͑0.5 l/min͒ transports the decomposed precursor material (CrO 3 ) and its related oxide phases (Cr 2 O 5 , Cr 3 O 8 ) into the deposition zone where the substrate is placed. The substrate temperature is adjusted to 390°C enabling the epitaxial growth of CrO 2 . Immediately after the growth the CrO 2 (100) films were i...
The molecular beam epitaxy (MBE) growth of bcc Fe(1 1 0) thin ®lms on an Al 2 O 3 (1 1 À2 0) substrate using Mo(1 1 0) seed layers has been investigated. The growth was studied by re¯ection high energy electron diraction (RHEED) in reciprocal space as well as by scanning tunneling microscopy in real space. The relative orientation between the lattices of the Fe (1 1
L XAFS spectra of polycrystalline Fe and Cr films are investigated by EXAFS and TEY (Total Electron Yield) techniques. A new method of obtaining local structure information from overlapping L XAFS spectra for 3d metals is proposed. Tikhonov regularization method of solving ill-posed problem is used. In contrast to the conventional methods (Fourier transformation and fitting procedures) this method does not demand any model assumption and any special procedure of deconvolution of L 1 -, L 2 -, L 3 -contributions. The parameters obtained from L XAFS spectra of polycrystalline Fe and Cr films (interatomic distance and coordination number for the first and the second coordination shells) agree with the expected crystallographic values. Up to now the regularization method was applied only to nonoverlapping XAFS spectra.
The growth of Co and Ag layers on wet‐processed H‐passivated Si(111) substrates by molecular beam epitaxy (MBE) has been studied using high resolution scanning tunneling microscopy (STM) with regard to possible applications of the layers in magnetoelectronic devices. Roughness and intermixing at interfaces as functions of deposition temperature and layer thickness are key parameters for the performance of such devices. The initial growth of Co and Ag and the influence of Ag atoms on the Si(111) surface reconstructions provide insight into adatom–substrate interactions.
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