Space charge effects in photoemission electron microscopy using amplified femtosecond laser pulses

Buckanie, Niemma M.; Göhre, J; Zhou, Ping; Linde, D. von der; Hoegen, M. Horn‐von; Heringdorf, F-J Meyer zu

doi:10.1088/0953-8984/21/31/314003

Cited by 59 publications

(38 citation statements)

References 24 publications

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“…In addition, the space charge effect may also degrade the spatial resolution. 43 We tested the real spatial resolution from Figure 1d. It was measured to be 15.0 (63.7) nm, which was slightly lower than the best spatial resolution (,8 nm) of our PEEM.…”

Section: Resultsmentioning

confidence: 99%

Direct imaging of the near field and dynamics of surface plasmon resonance on gold nanostructures using photoemission electron microscopy

et al. 2013

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Localized surface plasmon resonance (LSPR) can be supported by metallic nanoparticles and engineered nanostructures. An understanding of the spatially resolved near-field properties and dynamics of LSPR is important, but remains experimentally challenging. We report experimental studies toward this aim using photoemission electron microscopy (PEEM) with high spatial resolution of sub-10 nm. Various engineered gold nanostructure arrays (such as rods, nanodisk-like particles and dimers) are investigated via PEEM using near-infrared (NIR) femtosecond laser pulses as the excitation source. When the LSPR wavelengths overlap the spectrum of the femtosecond pulses, the LSPR is efficiently excited and promotes multiphoton photoemission, which is correlated with the local intensity of the metallic nanoparticles in the near field. Thus, the local field distribution of the LSPR on different Au nanostructures can be directly explored and discussed using the PEEM images. In addition, the dynamics of the LSPR is studied by combining interferometric time-resolved pump-probe technique and PEEM. Detailed information on the oscillation and dephasing of the LSPR field can be obtained. The results identify PEEM as a powerful tool for accessing the near-field mapping and dynamic properties of plasmonic nanostructures. Keywords: femtosecond laser; local field enhancement; near-field imaging; photoemission electron microscopy; surface plasmon resonance INTRODUCTION Because of the rapid development of nanofabrication techniques, metallic nanostructures that can exhibit localized surface plasmon resonance (LSPR) can be fabricated using several methods. The resonance frequency and amplitude of LSPR on metallic nanostructures are known to depend on the metal materials, shapes, and surrounding media. [1][2][3][4] In addition, the LSPR can confine optical fields in nanoscale space, leading to the so-called local field enhancement effect. These unique properties promote the application of LSPR in many fields, such as surface-enhanced Raman scattering, 5-8 sensing, 1,9,10 plasmonassisted photochemical reactions 4,11,12 and photocurrent generation. [13][14][15] To further understand the LSPR mechanism and to optimize the design of the plasmonic nanostructures for most applications, the near-field properties of the LSPR fields (especially the near-field distribution of the plasmonic nanostructures) must be determined. To date, investigations of the optical properties of LSPR have largely relied on far-field spectroscopic techniques or numerical simulations. Several experimental approaches have been utilized to visualize the near field, including scanning photoionization microscopy, 16,17 scanning near-field optical microscopy, 18-21 nonlinear luminescence or fluorescent microscopy, 22,23 nonlinear photopolymerization 24,25 and near-field ablation of a substrate. [26][27][28][29] However, these approaches have

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Section: Resultsmentioning

confidence: 99%

Direct imaging of the near field and dynamics of surface plasmon resonance on gold nanostructures using photoemission electron microscopy

et al. 2013

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“…All of these electrons have to pass the immersion lens system as the energy filtering of the photoelectrons takes place only further upstream in the instrument. Very high photocurrent densities can lead to undesirable sample charging or loss of image quality due to space charge effects in the electron optics, 20,21 especially in crossover regions of the electron trajectories, for example, the contrast aperture.…”

Section: B Spatial Resolution and Space-charge Effectsmentioning

confidence: 99%

Bulk sensitive hard x-ray photoemission electron microscopy

Patt

Wiemann

Weber

et al. 2014

Review of Scientific Instruments

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Hard x-ray photoelectron spectroscopy (HAXPES) has now matured into a well-established technique as a bulk sensitive probe of the electronic structure due to the larger escape depth of the highly energetic electrons. In order to enable HAXPES studies with high lateral resolution, we have set up a dedicated energy-filtered hard x-ray photoemission electron microscope (HAXPEEM) working with electron kinetic energies up to 10 keV. It is based on the NanoESCA design and also preserves the performance of the instrument in the low and medium energy range. In this way, spectromicroscopy can be performed from threshold to hard x-ray photoemission. The high potential of the HAXPEEM approach for the investigation of buried layers and structures has been shown already on a layered and structured SrTiO3 sample. Here, we present results of experiments with test structures to elaborate the imaging and spectroscopic performance of the instrument and show the capabilities of the method to image bulk properties. Additionally, we introduce a method to determine the effective attenuation length of photoelectrons in a direct photoemission experiment.

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“…Thus, we expect that the pure geometrical broadening is the most important effect in distorting the images. It was found in 2PPE or 3PPE microscopy experiments using a laser system operating at 1 kHz repetition rate (as ours) that the intensity had to be reduced to levels where imaging was only possible by measurements over 15 min [49]. In this case, the space charge problems were believed to occur at the crossover point near the entrance to the hemispherical energy analyzer incorporated in the design, when the electrons are decelerated to 1 keV.…”

Section: Experimental Setup and Requirementsmentioning

confidence: 81%

Imaging Localized Surface Plasmons by Femtosecond to Attosecond Time‐Resolved Photoelectron Emission Microscopy – “ATTO‐PEEM”

Chew

Pearce

Scheffold

et al. 2014

Attosecond Nanophysics

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The direct detection of the spatiotemporal dynamics of nanolocalized optical near-fields on nanostructured metal surfaces, for example, imaging of localized surface plasmons (cf. Chapter 1) on rough or nanostructured metal films or the imaging of propagating surface plasmon polaritons at a vacuum-metal or metal-dielectric interface is a prerequisite to further control and optimize surface-plasmon based ultrafast nanooptics for future device development and applications [1][2][3][4].While free electrons in metals collectively respond to excitation from a light pulse, which is resonant to the surface plasmon frequency of the system, and squeeze and amplify the field intensity of the incoming plane light field into a subwavelength spatial volume, the typically broad frequency bandwidth of surface plasmon resonances supports an ultrafast response of these fields with rapid field changes on sub-femtosecond time scales [5].The sub-wavelength nanoscaled localization of optical fields in the vicinity of metal nanostructures and the ultrafast temporal evolution of such fields on a 0.1-100 fs time scale require the invention and development of new experimental methodologies, which combine nanometer (sub-optical) spatial resolution, sub-femtosecond temporal resolution, and optionally further nanospectroscopic information.Resolving the spatial distribution of such fields requires a microscopic technique with sub-optical spatial resolution, for example, in the 10-100 nm range. Scanning near-field optical microscopy (SNOM) techniques have been successfully applied with spatial resolutions of about ∼100 nm; however, the combination with ultrashort light pulses is still very difficult. Photoemission electron microscopy (PEEM) is a technique capable of resolving the spatial emission distribution of photoelectrons with an ultimate resolution of ∼10 nm.

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Space charge effects in photoemission electron microscopy using amplified femtosecond laser pulses

Cited by 59 publications

References 24 publications

Direct imaging of the near field and dynamics of surface plasmon resonance on gold nanostructures using photoemission electron microscopy

Direct imaging of the near field and dynamics of surface plasmon resonance on gold nanostructures using photoemission electron microscopy

Bulk sensitive hard x-ray photoemission electron microscopy

Imaging Localized Surface Plasmons by Femtosecond to Attosecond Time‐Resolved Photoelectron Emission Microscopy – “ATTO‐PEEM”

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