Nanoscale terahertz STM imaging of a metal surface

Luo, Yang; Jelic, Vedran; Chen, Gong; Nguyen, Peter H.; Liu, Yu-Jui Ray; Calzada, Jesus A. M.; Mildenberger, Daniel J.; Hegmann, Frank A.

doi:10.1103/physrevb.102.205417

Cited by 39 publications

(24 citation statements)

References 47 publications

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“…The signal peaks at 0.12 electrons per pulse (τ = 0 ps), and the ultrafast recovery has a signal magnitude of only 0.04 electrons per pulse. This highlights the advantage of using a high repetition rate source for ultrafast measurements in the STM: whereas the measurement’s noise floor of 35 fA is comparable to previous reports of THz-coupled STM, 35 the high repetition rate of 41 MHz transduces this to a minimum detectable THz-induced current of 5 × 10 –3 electrons per pulse and enables measurements in the quantum limit of single-electron tunneling.…”

Section: Femtosecond Dynamics In the Single-electron Tunneling Regimesupporting

confidence: 62%

Variable Repetition Rate THz Source for Ultrafast Scanning Tunneling Microscopy

et al. 2021

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Broadband THz pulses enable ultrafast electronic transport experiments on the nanoscale by coupling THz electric fields into the devices with antennas, asperities, or scanning probe tips. Here, we design a versatile THz source optimized for driving the highly resistive tunnel junction of a scanning tunneling microscope. The source uses optical rectification in lithium niobate to generate arbitrary THz pulse trains with freely adjustable repetition rates between 0.5 and 41 MHz. These induce subpicosecond voltage transients in the tunnel junction with peak amplitudes between 0.1 and 12 V, achieving a conversion efficiency of 0.4 V/(kV/cm) from far-field THz peak electric field strength to peak junction voltage in the STM. Tunnel currents in the quantum limit of less than one electron per THz pulse are readily detected at multi-MHz repetition rates. The ability to tune between high pulse energy and high signal fidelity makes this THz source design effective for exploration of ultrafast and atomic-scale electron dynamics.

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Section: Femtosecond Dynamics In the Single-electron Tunneling Regimesupporting

confidence: 62%

Variable Repetition Rate THz Source for Ultrafast Scanning Tunneling Microscopy

et al. 2021

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“…Consequently, the conventional method of STS is incompatible with the key aspect of lightwave-driven tunnelling that makes ultrafast time resolution possible, and an alternate approach is required for THz-STS. Here, THz-STS spectra are recorded by sweeping the peak field strength of the incident terahertz pulse while maintaining a uniform waveform shape, then inverting the polarity and repeating 10 , 11 , 13 , 16 .…”

Section: Resultsmentioning

confidence: 99%

“…Electro-optic sampling in the far-field provides the terahertz electric field transient focused onto the STM tip (Figs. 2 e and f ), but antenna effects 11 , 14 , 17 and geometrical features on the scale of the terahertz wavelength 12 , 13 , 16 , 17 can modify its shape. Therefore, in-situ characterization of the near-field waveform is needed 13 , 14 , 17 , 30 , e.g., photoemission sampling (PES, see Supplementary Fig.…”

Section: Resultsmentioning

confidence: 99%

“…It has enabled femtosecond pump-probe experiments 8 , 9 , 13 , 19 , field-driven electroluminescence 20 , and the application of atomic-scale ultrafast forces 15 , 17 . Ultrafast fields can also operate in regimes inaccessible to conventional static STM fields, for example through lightwave-control of extreme tunnel currents 10 – 12 , 16 , 21 . The natural next step is to bring these capabilities to bear on novel material systems to inform design and synthesis.…”

Section: Introductionmentioning

confidence: 99%

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Lightwave-driven scanning tunnelling spectroscopy of atomically precise graphene nanoribbons

et al. 2021

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Atomically precise electronics operating at optical frequencies require tools that can characterize them on their intrinsic length and time scales to guide device design. Lightwave-driven scanning tunnelling microscopy is a promising technique towards this purpose. It achieves simultaneous sub-ångström and sub-picosecond spatio-temporal resolution through ultrafast coherent control by single-cycle field transients that are coupled to the scanning probe tip from free space. Here, we utilize lightwave-driven terahertz scanning tunnelling microscopy and spectroscopy to investigate atomically precise seven-atom-wide armchair graphene nanoribbons on a gold surface at ultralow tip heights, unveiling highly localized wavefunctions that are inaccessible by conventional scanning tunnelling microscopy. Tomographic imaging of their electron densities reveals vertical decays that depend sensitively on wavefunction and lateral position. Lightwave-driven scanning tunnelling spectroscopy on the ångström scale paves the way for ultrafast measurements of wavefunction dynamics in atomically precise nanostructures and future optoelectronic devices based on locally tailored electronic properties.

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“…The finding triggered a flurry of research activities which soon led to the mapping of the vibrational response of a single molecule (pentacene) with atomic spatial resolution [327], and to the control of the tunneling current through single atoms on Si surfaces [328]. The technique itself and its applications are now being explored intensively [329][330][331][332]. Even excitation at shorter wavelengths has recently been studied again with IR pump, THz probe experiments on C 60 multilayer structures [333].…”

Section: Thz Nanoimaging and Nanoscopymentioning

confidence: 99%

Roadmap of Terahertz Imaging 2021

Valušis

Lisauskas

Yuan

et al. 2021

Sensors

191

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In this roadmap article, we have focused on the most recent advances in terahertz (THz) imaging with particular attention paid to the optimization and miniaturization of the THz imaging systems. Such systems entail enhanced functionality, reduced power consumption, and increased convenience, thus being geared toward the implementation of THz imaging systems in real operational conditions. The article will touch upon the advanced solid-state-based THz imaging systems, including room temperature THz sensors and arrays, as well as their on-chip integration with diffractive THz optical components. We will cover the current-state of compact room temperature THz emission sources, both optolectronic and electrically driven; particular emphasis is attributed to the beam-forming role in THz imaging, THz holography and spatial filtering, THz nano-imaging, and computational imaging. A number of advanced THz techniques, such as light-field THz imaging, homodyne spectroscopy, and phase sensitive spectrometry, THz modulated continuous wave imaging, room temperature THz frequency combs, and passive THz imaging, as well as the use of artificial intelligence in THz data processing and optics development, will be reviewed. This roadmap presents a structured snapshot of current advances in THz imaging as of 2021 and provides an opinion on contemporary scientific and technological challenges in this field, as well as extrapolations of possible further evolution in THz imaging.

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Nanoscale terahertz STM imaging of a metal surface

Cited by 39 publications

References 47 publications

Variable Repetition Rate THz Source for Ultrafast Scanning Tunneling Microscopy

Variable Repetition Rate THz Source for Ultrafast Scanning Tunneling Microscopy

Lightwave-driven scanning tunnelling spectroscopy of atomically precise graphene nanoribbons

Roadmap of Terahertz Imaging 2021

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