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Metallic tips

Nelson et al. [34] determined from void shapes that the ratio 7100/7110 was 1.2, 0.98 and 1.14 for copper at 600°C, aluminum at 550°C, and molybdenum at 2000°C, respectively, and 1.03 for 7100/7111 for aluminum at 450°C. Metal tips in field emission studies (see Section VIII-2C) tend to take on an equilibrium faceting into shapes agreeing fairly well with calculations [133]. [Pg.280]

FIM Field ion microscopy [63, 62, 103] He ions are formed in a high field at a metal tip Surface structure... [Pg.313]

Microwaves from the waveguide are coupled into the resonator by means of a small coupling hole in the cavity wall, called the iris. An adjustable dielectric screw (usually machined from Teflon) with a metal tip adjacent to the iris pennits optimal impedance matching of the cavity to the waveguide for a variety of samples with different dielectric properties. With an appropriate iris setting the energy transmission into the cavity is a maximum and simultaneously reflections are minimized. The optimal adjustment of the iris screw depends on the nature of the sample and is found empirically. [Pg.1560]

In STM, a sharp metal tip [12] is brought within less than a nanometre of a conducting sample surface, using a piezoelectric drive (fignre B 1,19,11 At these separations, there is overlap of the tip and sample wavefiinctions at the... [Pg.1677]

Titanium Phosphides. The titanium phosphides (154) include Ti P [12037-66-0], Ti P, and TiP (163). Titanium monophosphide [12037-65-9] TiP, can be prepared by beating phosphine with titanium tetrachloride or titanium sponge. Alternatively, titanium metal may be heated with phosphoms ia a sealed tube. The gray metallic TiP is slightly phosphoms-deficient (TiPQ has a density of 408(0) kg/m, and displays considerable... [Pg.133]

The fact that the dielectric constant depends on the frequency gives SPFM an interesting spectroscopic character. Local dielectric spectroscopy, i.e., the study of s(w), can be performed by varying the frequency of the applied bias. Application of this capability in the RF range has been pursued by Xiang et al. in the smdy of metal and superconductor films [39,40] and dielectric materials [41]. In these applications a metallic tip in contact with the surface was used. [Pg.253]

Figure 2.6 Raman spectrum of an adenine nanocrystal obtained (a) with and (b) without the metallic tip. Spectrum (a) corresponds to the tip-enhanced near-field Raman spectrum while spectrum (b) shows the conventional micro-Raman spectrum. Figure 2.6 Raman spectrum of an adenine nanocrystal obtained (a) with and (b) without the metallic tip. Spectrum (a) corresponds to the tip-enhanced near-field Raman spectrum while spectrum (b) shows the conventional micro-Raman spectrum.
CARS spectroscopy utilizes three incident fields including a pump field (coi), a Stokes field (CO2 C02nonlinear polarization at cOcars = 2c0i — CO2. When coi — CO2 coincides with one of the molecular-vibration frequencies of a given sample, the anti-Stokes Raman signal is resonantly generated [22, 23]. We induce the CARS polarization by the tip-enhanced field at the metallic tip end of the nanometric scale. [Pg.29]

The force effect is applicable to investigation of the mechanical properties of nanomaterials [28, 29]. We measured TERS spectra of a single wall carbon nanotube (SWCNT) bundle with a metallic tip pressing a SWCNT bundle [28]. Figure 2.13a-e show the Raman spectra of the bundle measured in situ while gradually applying a force up to 2.4 nN by the silver-coated AFM tip. Raman peaks of the radial breathing... [Pg.35]

Sanchez, E. J., Novotny, L. and Xie, X. S. (1999) Near-field fiuorescence microscopy based on two-photon excitation with metal tips. Phys. Rev. Lett., 82, 4014-4017. [Pg.37]

Hayazawa, N Inouye, Y Sekkat, Z. and Kawata, S. (2000) Metallized tip amplification of near-field Raman scattering. Opt. Commun., 183, 333-336. [Pg.37]

SECM-induced transfer [SECMIT Fig. 2(b)] can be used to characterize reversible phase transfer processes at a wide variety of interfaces. The basic idea is to perturb the process, initially at equilibrium, through local amperometry at the UME. Hitherto, diffusion-limited electrolysis has mainly been used in conjunction with metal tips, but ion transfer voltammetric probes (discussed briefly in Section III, and in detail in Chapter 15) can also be used. The application of a potential to the tip, sufficient to deplete the... [Pg.292]

Figure 3.13 Three methods of chemically etching metal tips for STM. In (a) the current cut-off is manually or electronically triggered when the end of the etched wire falls the finite time delay inherent in this approach results in a blunting of the final tip as etching continues after separation, (b) This shows an adaptation in which the etching current is automatically cut off when the lower portion of the wire drops - it is the lower portion that is used as an STM tip. (c) This shows an improved design in which the etching current is fed to the lower portion of the tungsten wire through an electrolyte held in a conductive beaker. In this case the upper portion of the etched wire is kept. Figure 3.13 Three methods of chemically etching metal tips for STM. In (a) the current cut-off is manually or electronically triggered when the end of the etched wire falls the finite time delay inherent in this approach results in a blunting of the final tip as etching continues after separation, (b) This shows an adaptation in which the etching current is automatically cut off when the lower portion of the wire drops - it is the lower portion that is used as an STM tip. (c) This shows an improved design in which the etching current is fed to the lower portion of the tungsten wire through an electrolyte held in a conductive beaker. In this case the upper portion of the etched wire is kept.
For in situ investigations of electrode surfaces, that is, for the study of electrodes in an electrochemical environment and under potential control, the metal tip inevitably also becomes immersed into the electrolyte, commonly an aqueous solution. As a consequence, electrochemical processes will occur at the tip/solution interface as well, giving rise to an electric current at the tip that is superimposed on the tunnel current and hence will cause the feedback circuit and therefore the imaging process to malfunction. The STM tip nolens volens becomes a fourth electrode in our system that needs to be potential controlled like our sample by a bipotentiostat. A schematic diagram of such an electric circuit, employed to combine electrochemical studies with electron tunneling between tip and sample, is provided in Figure 5.4. To reduce the electrochemical current at the tip/solution... [Pg.122]

The scanning tunneling microscope (STM) is an excellent device to obtain topographic images of an electrode surface [1], The principal part of this apparatus is a metal tip with a very fine point (see Fig. 15.1), which can be moved in all three directions of space with the aid of piezoelectric crystals. All but the very end of the tip is insulated from the solution in order to avoid tip currents due to unwanted electrochemical reactions. The tip is brought very close, up to a few Angstroms, to the electrode surface. When a potential bias AF, usually of the order... [Pg.197]

Less generally applicable than electron or scanning probe microscopy, but capable of revealing great detail, are field emission and field ion microscopy (FEM and F1M). These techniques are limited to the investigation of sharp metallic tips, however, with the attractive feature that the facets of such tips exhibit a variety of crystallographically different surface orientations, which can be studied simultaneously, for example in gas adsorption and reaction studies. [Pg.183]

Pulling of wire until cleavage results in metal tip formations... [Pg.249]

More detailed studies of surface structure can be carried out using scanning tunneling microscopy (STM). For the use of this technique, a metal tip is scanned over the surface, and the distance from the tip to the surface is determined by the tunneling current between them. Images of surfaces with subnanometer resolution are often obtained using this method. [Pg.344]

Multimeters have sockets into which test leads are inserted. Test leads are insulated wires that have banana plugs on one end, for insertion into the sockets, and metal tips on the other end, for contacting the points in the circuit that are being measured. [Pg.168]

Most electrochemical experiments need an electrical contact of some kind to the silicon substrate. Because of the semiconducting nature of silicon a metallic tip or clip attached to the surface will not produce an ohmic contact but constitutes a Schottky junction. However, for some applications, like the ELYMAT (Section 10.3), where the contact is only operated under forward conditions at low current densities, such a contact is sufficient. For silicon samples with a doping concentration in excess of 1019 cnT3 the contact to a metal becomes ohmic. An ohmic contact to a silicon sample with a doping concentration below 1019 cm-3 can be achieved in different ways ... [Pg.14]

Fig. 13.7 Carbon nanotube field emitter grown on metal tip (courtesy M. Mann). Fig. 13.7 Carbon nanotube field emitter grown on metal tip (courtesy M. Mann).
Scanning probe microscopy was invented by Binnig and Rohrer (Nobel Prize, 1986) (Birdi, 2002a). Scanning tunneling microscope (STM) was based on scanning a probe (metallic tip) since it is a sharp tip just above the substrate, while monitoring... [Pg.215]

STM The tunneling current between a metallic tip and a conducting substrate that are in very close proximity but not actually in physical contact. This is controlled by piezomotors in a stepwise method. [Pg.216]


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