Ion bombardment cleaning

The intensities of these five beams, as represented by the peak maximum corrected for background, are plotted in Figure 3 as a function of exposure to oxygen. The rate of decrease of the beams from nickel with increasing exposure is approximately the same for a surface which has been well annealed as for one which has received a small anneal after ion bombardment cleaning. (The initial increase of the 57-volt... 

Fio. 8. Diffraction beam intensities as a function of oxygen exposure obtained after a small anneal of the crystal subsequent to ion-bombardment cleaning. Curve 1 Typical beam, in the (110) azimuth at about 28 volts, from the clean nickel lattice. Multiply the ordinate scale by 2 to obtain intensity. Curve 2 Typical beam, in the (001) azimuth at about 58 volts, from the clean nickel lattice. Multiply the ordinate scale hy 6. Curve 3 Typical beam, in the (110) azimuth at about 17 volts, from a double-spaced, face-centered lattice. Curve 4 Typical beam, in the (001) azimuth at about 27 volts, from a single-spaced, simple-square lattice. Multiply the ordinate scale by 2. Curve 5 Typical beam, in the (110) azimuth at about 22 volts, from a nickel oxide lattice. [From Farnsworth and Madden (27).]... 

In a recent study of CO adsorbed on an ion bombardment cleaned Ni(lOO) crystal, Armstrong 210) showed that an ordering of the adsorbed CO could be easily induced by a low energy electron beam and that... 

Winograd N, Garrison B, Harrison DE (1978) Angular distributions of ejected particles liom ion-bombarded clean and reacted single-crystal surfaces. Phys Rev Lett 41 1120-1123. doi 10. 1103/PhysRevLett.41.1120... 

Once a sample is properly oriented and polished, it is placed into a UHV chamber for the final preparation steps. Samples are processed in situ by a variety of methods in order to produce an atomically clean and flat surface. Ion bombardment and aimealing (IBA) is the most conunon method used. Other methods include cleaving and film growth. 

Plant capacity is a function of feed size distribution and Hberation. Separators can accept a size range as wide as 50—1000 p.m. Capacities are typically 1000 2500 kg/(h-m) based on rotor length which could be up to 3 m and have dia 150—250 mm. The feed should be as dry as possible because moisture interferes seriously with separation. Heaters are usually provided before the feed enters the charged field. Final cleaning is often conducted in electrostatic-type separators. Electrostatic shape separation, a newer form of ion bombardment separation, involves separation of particles based on shape and density without consideration to conductivities (37). 

Charging bv ion bombardment is the technique used in most mineral separations. The conductive-induction (nonionizing) plate types of separators have also been used Application.s of this device in the minerals indiisti v include its use as a final cleaning step when concentrating rutile and zircon,... 

Figure 1.7 Ion plating device in which the substrate is cleaned by ion bombardment and the material to be deposited is supplied by a Knudsen cell...

The chemical and electronic properties of elements at the interfaces between very thin films and bulk substrates are important in several technological areas, particularly microelectronics, sensors, catalysis, metal protection, and solar cells. To study conditions at an interface, depth profiling by ion bombardment is inadvisable, because both composition and chemical state can be altered by interaction with energetic positive ions. The normal procedure is, therefore, to start with a clean or other well-characterized substrate and deposit the thin film on to it slowly at a chosen temperature while XPS is used to monitor the composition and chemical state by recording selected characteristic spectra. The procedure continues until no further spectral changes occur, as a function of film thickness, of time elapsed since deposition, or of changes in substrate temperature. 

The Ti02 (001) surface was cleaned and reduced by cycles of ion bombardment as previously described [3]. The distribution of titanium oxidation states was determined from cxirve fitting the Ti(2p3/2) envelope in x-ray photoelectron spectra [3]. After surface preparation, reaction experiments were conducted in either the TPD or steady state mode. TPD experiments have been described [1]. XPS spectra were also obtained following a saturation exposure of the sample using the same procedure as that for the TPD experiments. After pump down, the crystal was placed under the Mg X-ray source and the Ti(2p), 0(ls), and C(ls) regions were scanned. For steady-state experiments a dosing needle was aligned perpendicular to the axis of the mass spectrometer. It was used to direct a steady beam of methylacetylene (Linde, 95%) at the crystal surface when the sample was placed at the aperture of the mass spectrometer. Steady state reaction experiments were... 

Figure 9 [171] shows the Au 4f emission of the nanoparticles at different steps of the sputtering. The as-cleaned spectrum (curve (a)) is equivalent to the published data of bulk gold. The Au/Si ratio was around 3.3, showing that the gold film was discontinuous. With further ion bombardment, the position of the 4f emission shifted to... 

Figure 9. Photoemission from 4f atomic level of Au after surface cleaning (a) and 15-min (b) and 30-min (c) Ar ion bombardment. (Reprinted from Ref [171], 2002, with permission from Elsevier.)...

Samples may either be those in which the surface of interest has been exposed to the environment before analysis, or the surface to be examined is created in the UHV chamber of the instrument. The latter method is generally preferable, and also argon-ion bombardment is commonly used to clean sample surfaces in situ in the spectrometer. In metallurgical studies, the fracture sample is particularly important the sample is machined to fit the sample holder, and a notch is cut at the desired point for fracture. The fracture stage is isolated from the analytical chamber and is pumped down to UHV. Liquid nitrogen cooling is often provided, as this encourages... 

Figure 2.5. XPS spectra produced from a sample of iron which has been cleaned by argon ion bombardment, using (a) Aluminium Ka radiation, and (b) Magnesium Ka radiation. (Reproduced by...

Spectra for a series of Cu-Ni alloys have been obtained (91) and these are reproduced in Fig. 11. Because of overlapping of peaks from the component metals, separate indications of each element are only obtained from the 925 eV Cu peak and the 718 eV Ni peak. The results have only qualitative significance because the quoted nickel concentrations are bulk values. Nevertheless, they do suggest that for these particular samples of Cu-Ni alloys, the surface composition varies smoothly from pure copper to pure nickel. Auger spectroscopy has subsequently shown that the surface composition of the (110) face of a 55% Cu-Ni crystal was identical with the bulk composition (95a). Ono et al. (95b) have used the technique to study cleaning procedures argon ion bombardment caused nickel enrichment of... 

Figure 66D was obtained for the same CdTe(lll) crystal after electrochemical reduction at -2.0 V for 2 minutes. Transitions for both Cd and Te are evident, and the Cd/Te peak height ratio is similar to that observed by other workers for stoichiometric CdTe [393,394]. In addition, well-ordered (1 X 1) LEED patterns (Fig. 67) were observed on both the CdTe(lll)-Cd and CdTe(lll)-Te faces. This is in contrast to CdTe surfaces prepared by ion bombardment, where postbombardment annealing was required to produce a LEED pattern, and the annealing appeared to result in formation of a reconstructed surface. In summary, well-ordered, clean, and unreconstructed CdTe surfaces have been produced using a wet etching/electrochemical treatment. 

Fig. 3.3. Auger electron spectra from (a) Si surface cleaned by 500 eV Ar ion bombardment and (b) same surface after bombardment with 5x 10 CF ions/cm (500 eV). (See Ref. )...

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