Photon-induced near-field electron microscopy (PINEM): theoretical and experimental

Park, Sang Tae; Lin, Milo M.; Zewail, Ahmed H.

doi:10.1088/1367-2630/12/12/123028

Cited by 306 publications

(458 citation statements)

References 38 publications

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“…A detailed derivation of the transition probability of PINEM in a non-relativistic formulation was given in Ref. 30 and summarized in Ref. 32, where the time-dependent 1D Schrödinger equation of a free electron under a scattered electromagnetic wave was analytically solved to first order.…”

Section: Photon-electron Couplingmentioning

confidence: 99%

“…The exponential function describes the overlapping of electrons with the incident light pulse at the position of particle, z = 0, in a slowly-varying envelope approximation. 30 For a weak interaction, we obtain…”

Section: Photon-electron Couplingmentioning

confidence: 99%

“…27,28 Theoretical accounts have been given by various groups. [29][30][31] Here, we present the imaging aspect of PINEM, in particular, the capability to visualize the optical near field by spatially mapping the photon-electron interaction, and compare it to that by EELS. In EELS, swift electrons induce a transient electric field with a continuous spectrum of frequency and excite plasmons in nearby particles.…”

Section: Introductionmentioning

confidence: 99%

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Photon-induced near-field electron microscopy

Barwick

Flannigan

Zewail

2009

Nature

647

642

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Ultrafast electron microscopy in the space and time domains utilizes a pulsed electron probe to directly map structural dynamics of nanomaterials initiated by an optical pump pulse, in imaging, diffraction, spectroscopy, and their combinations. It has demonstrated its capability in the studies of phase transitions, mechanical vibrations, and chemical reactions. Moreover, electrons can directly interact with photons via the near field component of light scattering by nanostructures, and either gain or lose light quanta discretely in energy. By energetically selecting those electrons that exchanged photon energies, we can map this photon-electron interaction, and the technique is termed photon-induced near field electron microscopy (PINEM). Here, we give an account of the theoretical understanding of PINEM. Experimentally, nanostructures such as a sphere, cylinder, strip, and triangle have been investigated. Theoretically, time-dependent Schrödinger and Dirac equations for an electron under light are directly solved to obtain analytical solutions. The interaction probability is expressed by the mechanical work done by an optical wave on a traveling electron, which can be evaluated analytically by the near field components of the Rayleigh scattering for small spheres and thin cylinders, and numerically by the discrete dipole approximation for other geometries. Application in visualization of plasmon fields is discussed.

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Section: Photon-electron Couplingmentioning

confidence: 99%

Section: Photon-electron Couplingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photon-induced near-field electron microscopy

Barwick

Flannigan

Zewail

2009

Nature

647

642

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“…The circled area is a typical probing area, covering haematite particle with a blank gap. Since the ratio of PINEM-electrons to probing electrons decreases away from the edge of the haematite particle to both sides, 2 and the width of the particle is obviously larger than the blank gap, the average ratio of PINEM-electrons to probing electrons in the blank gap area should be stronger than that on the haematite. All the PINEM-electrons contribute to the broadening of the zero-loss spectra, while only the electrons passing through the haematite contribute to the Fe L3-edge.…”

Section: S2mentioning

confidence: 99%

Ultrafast Elemental and Oxidation-State Mapping of Hematite by 4D Electron Microscopy

Baskin

Zhou

et al. 2017

J. Am. Chem. Soc.

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A. PINEM-electron effect on the broadening of the core-loss edge (PINEM stands for photo-induced near-field electron microscopy) Figure S1. (a) Zero-loss EELS spectrum at negative time before excitation. (b) PINEM-electron effect on the zero-loss spectrum at 0 ps. (c) Ultrafast TEM image using zero-loss electrons. (d) PINEM image using electrons gaining single photon energy at 0 ps. A 2 eV energy slit was used to select electrons to create images in c and d, and the circled area is typical probing area.

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“…For instance, it was observed in photo-induced near-field electron microscopy (PINEM), invented by Zewail and co-workers [17][18][19] , that the intensities of both electron energy-loss and energy-gain peaks became compatible with the zero-loss (elastic) peak under excitation of SPRs induced by ultrafast lasers. However, it should be emphasized that in their experiments the generation of SPRs and electron scattering come from two separate sources and the electron energy-loss spectra could still be treated by the linear response 17,19 .…”

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confidence: 99%

Nonlinear inelastic electron scattering revealed by plasmon-enhanced electron energy-loss spectroscopy

Liu

Zhang

et al. 2014

Nature Phys

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Electron energy-loss spectroscopy is a powerful tool for identifying the chemical composition of materials [1][2][3][4][5] . It relies mostly on the measurement of inelastic electrons, which carry specific atomic or molecular information. Inelastic electron scattering, however, has a very low intensity, often orders of magnitude weaker than that of elastically scattered electrons. Here, we report the observation of enhanced inelastic electron scattering from silver nanostructures, the intensity of which can reach up to 60% of its elastic counterpart. A home-made scanning probe electron energy-loss spectrometer 6 was used to produce highly localized plasmonic excitations, significantly enhancing the strength of the local electric field of silver nanostructures. The intensity of inelastic electron scattering was found to increase nonlinearly with respect to the electric field generated by the tip-sample bias, providing direct evidence of nonlinear electron scattering processes. Figure 1a gives a schematic drawing of the scanning probe electron energy-loss spectroscopy (SP-EELS) technique used in this study, the details of which can be found elsewhere 6 . Briefly, it consists of a tip-sample system and a toroidal electron energy analyser (TEEA). The experimental arrangement is sketched in Fig. 1b. A tip made from a 0.42 mm tungsten wire by electrochemical etching is approached to a distance of micrometres from the grounded sample surface, which is prepared by evaporating a 30 nm thin film of Ag on freshly cleaved highly ordered pyrolytic graphene (HOPG). Silver structures with dimensions of tens of nanometres are observed on the sample surface, as illustrated in the inset of Fig. 1b. Electrons are field-emitted from the tip when a negative tip voltage V t of hundreds of volts is applied, and surface plasmon resonance (SPR) of the Ag nanostructures is excited by the field-emission electrons under a strong electric field introduced by the tip-sample bias. The backscattered electrons from the sample surface are collected and analysed by the TEEA. In this way the electron energy-loss spectroscopy (EELS) under a certain tip-sample distance and tip voltage can be acquired.It should be mentioned that EELS has been applied for decades to detect surface plasmons 1,7-14 , and in combination with a scanning transmission electron microscope (STEM) it is capable of mapping the spatial variation of SPRs at the nanoscale 11-14 . The energy-loss feature of Ag systems has been studied extensively by EELS, including low-energy backscattering EELS (refs 1,10) and high-energy transmission EELS (refs 11,13,14). A typical EELS spectrum of Ag nanostructures is shown in Fig. 1c, which was obtained at a tip-sample distance of 114 µm with a tip voltage of −246 V and a sample current of 10 pA. The energy-loss peak located at about 3.7 eV is associated with the SPR excitation of Ag. Our spectrum is in excellent agreement with those reported by Palmer's group, who also used scanning probe electron spectroscopy to investigate the EELS of Ag sur...

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Photon-induced near-field electron microscopy (PINEM): theoretical and experimental

Cited by 306 publications

References 38 publications

Photon-induced near-field electron microscopy

Photon-induced near-field electron microscopy

Ultrafast Elemental and Oxidation-State Mapping of Hematite by 4D Electron Microscopy

Nonlinear inelastic electron scattering revealed by plasmon-enhanced electron energy-loss spectroscopy

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