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Atomic metallic ion emission

Binh and Garcia (1991, 1992) reported that, at temperatures around one third of the bulk melting temperature, by applying an even higher electric field to th tip, the metal ions move to the protrusions and emit from the ends. Sharp, pyramidal nanotips, often ending with a single atom, can be reproducibly generated. The experiment was performed on W, Au and Fe tips. In particular, for W tips, the conditions to observe metal ion emission arc electrical field, 4-6 kV, or 1.2-1.8 eV/A and temperature, 1200-1500 K. This new phenomenon is termed the atomic metallic ion emission (AMIE). [Pg.289]

The AMIE is different from the standard field ionization or evaporation. The emitted positive ion beams, with a flux of approximately 10 ions/sec, are obtained under ultra-high vacuum conditions (wl0 Torr). Due to the ultra-high vacuum, the observed ion beams cannot be due to the impurities in the vacuum chamber. Also, the beam is very difficult to deflect by an external magnetic field, indicating that they consist of heavy ions. Furthermore, the emitted ion beam is highly collimated, and form a sharp image of the tip [Pg.290]

Structure on the fluorescent screen. By comparing the metal ion image with FIM and FEM, it is confirmed that the metal ions come from the single-atom protrusions on the tip apex. The FIM and FEM studies also confirmed that most of the protrusions generated through this process ended with a single metal atom. [Pg.291]

The tip treatment can be done during actual tunneling. Often, these in situ tip treatments take a few seconds to complete. The effect of the tip treatment process can be verified by actual imaging immediately. If one action is not successful, another action can proceed immediately—it takes a few more seconds. As we have mentioned at the beginning of this chapter, these methods was already used at the birth of the STM by the inventors in their first set of experiments (Binnig and Rohrer, 1982). [Pg.291]


Fig. 13.8. Atomic metallic ion emission and nanotip formation, (a) At high temperature, the atoms on a W tip becomes mobile. The tip surface is macroscopically flat but microscopically rough, (b) By applying a high field (1.2-1.8 V/A,), the W atoms move to the protrusions, (c) The apex atom has the highest probability to be ionized and leave the tip. The W ions form an image of the tip on the fluorescence screen, (d) A well-defined pyramidal protrusion, often ended with a single atom, is formed. By cooling down the tip and reversing the bias, a field-emission image is observed on the fluorescence screen. The patterns are almost identical. (Reproduced from Binh and Garcia, 1992, with permission.)... Fig. 13.8. Atomic metallic ion emission and nanotip formation, (a) At high temperature, the atoms on a W tip becomes mobile. The tip surface is macroscopically flat but microscopically rough, (b) By applying a high field (1.2-1.8 V/A,), the W atoms move to the protrusions, (c) The apex atom has the highest probability to be ionized and leave the tip. The W ions form an image of the tip on the fluorescence screen, (d) A well-defined pyramidal protrusion, often ended with a single atom, is formed. By cooling down the tip and reversing the bias, a field-emission image is observed on the fluorescence screen. The patterns are almost identical. (Reproduced from Binh and Garcia, 1992, with permission.)...
Binh, V. T., and Garcia, N. (1991). Atomic metallic ion emission, field surface melting, and scanning tunneling microscopy tips. J. Phys. I. 1, 605-612. [Pg.385]

See Atomic metallic ion emission Anomalous corrugation theory 31, 142 breakdown 146 graphite, and 31, 144 Apparent barrier height 63,171 anomalously low 171 attractive force, and 49, 209 definition 7 image force, and 72 repulsive force, and 171, 198, 209 square-barrier problem, in 63 Apparent radius of an atomic state 153 Atom charge superposition I 11 analytic form 111 Au(lll), in 138 in atomic beam scattering 111 Atom-beam diffraction 107 apparatus 109... [Pg.405]

Atomic force microscope (continued) biological applications 341 electrochemistry, in 323 liquid-solid interface, at 323 NaCI, image of 322 repulsive-force mode 314, 321 Atomic metallic ion emission 289—291 Atomic units 174... [Pg.405]

Tip treatment 281—293, 301 annealing 286 annealing with a field 288 atomic metallic ion emission 289 controlled collision 293 controlled deposition 288 field evaporation 287 for scanning tunneling spectroscopy 301 high-field treatment 291 Tip wavefunctions 76—81 explicit forms 77 Green s functions, and 78 Tip-state characterization 306, 308 ex situ 306 in situ 308... [Pg.411]

Recalling Figure 9.4, we know that thermal energy sources, such as a flame, atomize metal ions. But we also know that that these atoms experience resonance between the excited state and ground state such that the emissions that occur when the atoms drop from the excited state back to the ground state can be measured. While there are several techniques that measure such emissions, including flame emissions... [Pg.261]

Eor example, street lamps use the emissions from excited sodium atoms, the dazzling colors of a fireworks display come from photons emitted by metal ions in excited states, and the red light in highway flares often comes from excited Sr ions. [Pg.533]


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