Polycrystalline Fe Films Research Articles

MCD Observed by Photoemission on the 2p Lines of Iron Films Under an External Applied Field.

ABSTRACTCircular Dichroic X-ray Photoemission Spectroscopy (CDXPS) experiments have been performed on the 2p core level spectra of polycrystalline Fe film which was magnetized by a low excitation field. The ability to perform the CDXPS experiments in a non remanent mode at a photon energy of 2100 eV opens new and interesting possibilities for the MCD technique in the study of surface and interface Magnetism. Our work on this polycrystalline iron gives some new insights into the understanding of the MCD Mechanism. First results show a similar angular variation for the measured asymmetry, as those observed on a Fe bcc (100) single crystal remanently magnetized in the [100] direction. Our results make clear that the parameters governing the behaviour of the asymmetry factor (A) are not completely described by the relative direction of the Magnetization (M) with the polarization vector of the incident beam (q) and the direction of detection of the photoelectrons (z). The specific outcoming of this work is to clearly show that this behaviour of A is not connected to the crystalline structure of the film for our geometries.

Effect of oxygen on orientation of polycrystalline Fe films prepared by ECR-magnetron sputtering

An ECR-magnetron sputtering system with permanent magnets has been developed and used to prepare Fe-O films. Oxygen was introduced into an Ar sputtering atmosphere during deposition of Fe onto the glass substrate. X-ray diffraction patterns of these films showed a drastic increase in intensity of the Fe(200) diffraction peak, and a rapid decrease of the Fe(110) peak. The Fe(110) single peak is observed in the film prepared without oxygen. In the films prepared with oxygen, iron oxides were not detected through x-ray diffraction, x-ray photoelectron, or magnetic properties measurements, implying that, in sputter-deposited Fe films, a small amount of oxygen brings about a [100] orientation of the Fe grains.

Quasi-two-dimensional ferromagnetism in polycrystalline Fe.

Ultrathin polycrystalline Fe films of an average thickness 5 \AA{} are prepared on a Ta substrate by ion-beam sputter deposition in ultrahigh vacuum. The Ta itself is deposited on top of a three-dimensional (3D) ferromagnet, and it acts as a nonmagnetic metallic spacer layer through which exchange fields ${\mathit{H}}_{\mathrm{ex}}$ of various strengths are transferred from the magnetic substrate into the overlayer ultrathin film. The temperature dependence of the magnetization M(T) of the overlayer film is obtained from measurement of the spin polarization of the low-energy cascade electrons. M(T) depends critically on the thickness x of the Ta nonmagnetic spacer layer. The magnetic transition of the overlayer film is increasingly smeared out as ${\mathit{H}}_{\mathrm{ex}}$ increases, yet the transition temperature ${\mathit{T}}_{\mathit{C}}$ is clearly defined down to x=3 \AA{}. In the context of crossover from 3D to 2D magnetism, ${\mathit{T}}_{\mathit{C}}$ increases with decreasing x in a manner consistent with the theory of phase transitions in quasi-2D systems. Adsorption of residual gas molecules such as CO changes the shape of M(T) but does not affect ${\mathit{T}}_{\mathit{C}}$. The nature of the changes suggests that adsorbed residual gas molecules act as surfactants that spread the film slightly on the substrate, thereby converting it from the superparamagnetic to the ferromagnetic state.

Amorphous FeTi alloy formed by solid state reaction

The present paper reports the formation of amorphous Fe 50Ti 50 alloy by the solid state reaction of pure polycrystalline Fe and Ti thin films at low temperature. X-ray diffraction and reflecting electron diffraction were used to monitor the reaction. The amorphization process of this alloy without large negative mixing heat isexplained in view of the rection kinetics.

CO 2 adsorption and reaction on polycrystalline Fe films

Thin iron films deposited under ultrahigh vacuum conditions are used as adsorbents. The adsorption and reaction of CO 2 on these films are studied by means of HeI and HeII UPS, XPS (C1s and O1s), changes in work function and adsorption calorimetry. As in the case of single crystal surfaces (Fe(111) and stepped Fe(110)) at 80 K linear CO 2 and a bent, anionic species are adsorbed. From the intensities of C1s and O1s signals it follows that this species is CO 2 − . With increasing temperature decomposition into CO+O takes place. This is also proved with the aid of calorimetric measurements. Already at room temperature a partial decomposition into C and O is observed. There are two carbon species, a carbidic and a graphitic one. The decomposition reactions set in at lower temperatures than in the case of the single crystal surfaces.

CO 2 adsorption and reaction on polycrystalline Fe films

CO 2 adsorption and reaction on polycrystalline Fe films

Selective area deposition of metals using low-energy electron beams

We have investigated the use of low-energy electron beams to nucleate and stimulate the deposition and growth of thin films of metals. Selective area growth of Fe from Fe(CO)5 using low-energy focused electron beams (<5 keV) has been deomnstrated. Low-energy electron-beam irradiation (0.5–3.0 keV) can be used to nucleate growth of Fe on a Si surface. Subsequent thermal decomposition of Fe(CO)5 on Fe is ∼900 times faster than on Si at 125 °C resulting in thick, polycrystalline Fe films deposited only in areas irradiated by the electron beam. We have demonstrated nucleation and growth of 150 nm Fe features using 3 keV, 100-nm-diam electron beam. Fluxes and energies of low-energy electrons passing through the surface (primaries, secondaries, backscatters) are calculated by a Monte Carlo technique using an accurate scattering cross section for low-energy electrons. Spatial distributions of backscatters and secondaries at primary energies <3000 eV are seen to be confined primarily to a radius of <10 nm from the point of impact, and it appears that scattering contributes little to the spatial distribution of deposited film. Minimal electron scattering at low-energy makes this regime attractive for direct write, selective area processing.

X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy study on the CO chemisorbed over amorphous FeNiB alloys

A surface study has been conducted to determine CO interaction with Fe80B20 and Fe40Ni40B20 samples in amorphous and crystalline forms in the presence and absence of H2. At 300 K molecular CO exists only on Ar+ etched surface of partially and fully crystallized FeNiB indicated by ultraviolet photoelectron spectroscopy (UPS) and x-ray photoelectron spectroscopy peaks at 8.3, 11.6, and 285.5 eV (C 1s), respectively, as well as by CO thermal desorption spectroscopy. CO dissociation revealed by UPS peaks at 5.6 eV also occurs. Oxide species of B, Fe, and Ni cannot be observed at all. On the other hand, at 570 K a C 1s peak appears representing a carbidic and graphitic species in the binding energy (B.E.) range of 283.2 and 284.6 eV, respectively. Regardless of the presence of H2, B is always oxidized on the surface, while Fe and Ni are maintained in metallic form. Since practically no difference exists between carbidic C 1s measured here and on polycrystalline Fe film, the unique high catalytic activity of partially crystallized FeNiB can be interpreted by a hindered transformation of the reactive carbon into its inactive form due to the optimum particle size distribution.

Spin-Polarized Neutron Reflection Measurements on Atomically Thin Magnetic Layers

We have enhanced the flipping ratio of spin-polarised-neutron near-critical-angle reflectivity measurements by sandwiching thin (few atomic layers) magnetic films (area 2 cm2) between non-magnetic materials, thereby producing interference in the neutron wave field within the sandwich structure. A strongly spin dependent reflectivity is observed for a 12 Å polycrystalline Fe film at 300 K but no spin dependence is observed for ultrathin f.c.c. Fe films at 300 K.

Dc magnetron- and diode-sputtered polycrystalline Fe and amorphous Tb(FeCo) films: Morphology and magnetic properties

We have prepared polycrystalline Fe and amorphous Tb(FeCo) films using both dc diode- and magnetron-sputtering techniques. Magnetic properties and aging characteristics of these films were measured by a vibrating sample magnetometer and an automatic torque magnetometer. Film morphologies were studied by transmission electron microscopy. The magnetic and aging characteristics are closely correlated to the film morphology. It was also found that different sputtering methods can be tailored to produce a similar film morphology. Among the sputtering parameters, the Ar pressure during deposition at room or lower temperature strongly influences the film morphology.

Photoemission study of single-crystal faces of iron

Energy-distribution curves (EDC's) of photoelectrons emitted normal to the surfaces of Fe(100), Fe(110), and Fe(111) have been measured using photon energies of 11.83, 16.85, and 21.22 eV. The results are interpreted by emission from electronic states of the corresponding symmetry lines in the three-dimensional Brillouin zone. The band structure of ferromagnetic Fe as computed by Singh et al. is found adequate to explain major features of the EDC's, whereas a band structure of the paramagnetic state cannot satisfactorily account for the results. The maximum of occupied states is observed at about 0.6 eV below the Fermi level in agreement with previous measurements of polycrystalline Fe films. Emission from surface states or resonances cannot be identified with certainty.

Even M-O transmission effects in thin ferromagnetic films

An even magneto-optic effect, consisting of a variation of the transmitted light intensity at normal incidence and when the magnetization vector rotates, has been measured on thin polycrystalline Ni, Fe and Co films versus wavelength (0.4-1.25 mu m range) for different film thicknesses and using a new and sensitive experimental set-up. The results are then compared with the existing theoretical models and calculations.

Measurement of the boundary widths of iron, nickel, and iron-nickel films

Polycrystalline Fe, Ni, and Ni-Fe films have been studied by electron microscopy. The boundary widths have been measured as a function of the initial composition of the material evaporated.

1362. Structure and growth of polycrystalline Fe and permalloy thin films: H M Wiedenmann and H Hoffmann, Z Angew Phys, 18(5–6), 12th Apr 1965, 502–506, (in German)

1362. Structure and growth of polycrystalline Fe and permalloy thin films: H M Wiedenmann and H Hoffmann, Z Angew Phys, 18(5–6), 12th Apr 1965, 502–506, (in German)

Relaxation Phenomenon in Magnetic Films with Stripe Domains

Slow reorientation of `stripe domains' driven by a constant ac magnetic field was observed by the Bitter technique in evaporated polycrystalline Ni, Fe, Co and Ni-Fe films. In terms of this effect, the relaxation phenomenon of B-H loops first observed by Huber and Smith in `mottled' Permalloy films was fully explained.