A fully coherent electron beam from a noble-metal covered W(111) single-atom emitter

Abstract

In quantum mechanics, a wavefunction contains two factors: the amplitude and the phase. Only when the probing beam is fully phase coherent, can complete information be retrieved from a particle beam based experiment. Here we use the electron beam field emitted from a noble-metal covered W(111) single-atom tip to image single-walled carbon nanotubes (SWNTs) in an electron point projection microscope (PPM). The interference fringes of an SWNT bundle exhibit a very high contrast and the fringe pattern extends throughout the entire beam width. This indicates good phase correlation at all points transverse to the propagation direction. Application of these sources can significantly improve the performance and expand the capabilities of current electron beam based techniques. New instrumentation based on the full spatial coherence may allow determination of the three-dimensional atomic structures of nonperiodic nanostructures and make many advanced experiments possible.

Noble-Metal Covered W(111) Single-Atom Electron Sources

“…However, this theorem assumes that the effective source is a collection of mutually uncorrelated emission points. For an electron source with the beam divergence as in Figure 8(a) and the electron energy of 89 eV, the smallest effective source size estimated from Heisenberg's uncertainty principle is 3.9 Å, which is significantly larger than the real size of a SAT (1 to 2 Å) (39). Therefore, the electron beam emitted from the SAT can be considered as a beam from a perfect point source and thus should be fully (spatially) coherent.…”

Интерференция При Туннельной Ионизации Электрона, Связанного Двумя Короткодействующими Потенциалами

“…Однако в таких экспериментах требуется решить дополнительные вопросы, связанные с выстраива-нием оси молекулярного иона в заданном направлении и учетом или фиксацией его пространственного положения. В то же время современные технологии позволяют создавать наноэмиттеры из набора острых наноиголок [21,22], а также в виде нанопирамиды с вершиной из одного атома [23]. Близкое расположение таких наноразмерных источников будет обусловливать интерференционные проявления в токе эмиссии [24,25].…”

Fabrication of ultra-sharp single atom tips

“…After years of efforts, many ultra-sharp tips including pyramidal single atom tips have been put into reality [1,2], and the numbers of research based on ultra-sharp tips are blooming [3,4]. However, the task of seeking out new way to achieve various ultra-sharp tips has never ceased.…”