Externally triggerable optical pump-probe scanning tunneling microscopy

Mogi, Hiroyuki; Wang, Zihan; Kikuchi, Ryusei; Yoon, Cheul Hyun; Yoshida, Shoji; Takeuchi, Osamu; Shigekawa, Hidemi

doi:10.7567/1882-0786/aaf8b2

Cited by 9 publications

(21 citation statements)

References 29 publications

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“…On the other hand, for t d < 0, since the THz pulse was irradiated after the IR pulse, as shown in the inset, I THz reflects the dynamics of the excited state due to photocarrier generation. Since 2H-MoTe 2 is a conventional semiconductor, in contrast to Bi 2 Se 3 , photocarriers excited by optical pulses induce a surface photovoltage, , leading to a change in I THz . Thus, the delay-time dependence of I THz for t d < 0 represents the carrier decay process in 2H-MoTe 2 .…”

Section: Resultsmentioning

confidence: 99%

Subcycle Transient Scanning Tunneling Spectroscopy with Visualization of Enhanced Terahertz Near Field

et al. 2019

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The recent development of optical technology has enabled the practical use of a carrier-envelope phase-controlled monocycle electric field in the terahertz (THz) regime. By combining this technique with metal nanostructures such as nanotips, which induce near-field enhancement, the development of novel applications is anticipated. In particular, THz scanning tunneling microscopy (THz-STM) is a promising technique for probing ultrafast dynamics with the spatial resolution of STM. However, the modulation of the THz waveform is generally accompanied by an enhancement of the electric field, which is unknown in actual measurement environments. Here, we present a method enabling direct evaluation of the enhanced near field in the tunnel junction in THz-STM in the femtosecond range, which is essential for the use of the THz near field. In the tunneling regime, it was also demonstrated that the transient electronic state excited by an optical pulse can be evaluated using the THz-STM, and the ultrafast carrier dynamics in 2H-MoTe2 excited by an optical pulse was reproducibly probed.

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Section: Resultsmentioning

confidence: 99%

Subcycle Transient Scanning Tunneling Spectroscopy with Visualization of Enhanced Terahertz Near Field

et al. 2019

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“…These approaches enable non-invasive imaging down to picosecond temporal resolution 21,22 . Improvement of the time resolution has been achieved by various means, such as recording the cantilever deflection read-out signal with ultra-high sampling rate as well as by overcoming the averaging limitation by applying high frequency pulses in excitation and detection [23][24][25][26] . The latter so-called pump-probe based approaches have been used in optical spectroscopy for decades and recently have been applied to SPM in order to resolve the local decay of the surface photovoltage in organic donor-acceptor blends, contact potential difference (CPD) changes in an organic transistor structure with microsecond temporal resolution, and picosecond relaxations of photovoltage in low temperature grown GaAs 27,28 .…”

Section: Introductionmentioning

confidence: 99%

“…As recent developments of advanced scanning probe microscopy (SPM) techniques now allow for the characterization of electrically and optically active materials with high temporal resolution, they offer insight into the spatial variation of charge carrier dynamics on multiple timescales. − These approaches enable noninvasive imaging down to picosecond temporal resolution. , Improvement of the time resolution has been achieved by various means, such as recording the cantilever deflection read-out signal with ultrahigh sampling rate as well as by overcoming the averaging limitation by applying high-frequency pulses in excitation and detection. − These approaches have been of particular interest for electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KPFM) applications. The EFM and KPFM techniques rely on the electrostatic force arising between the AFM probe and the sample, separated by a distance z, upon application of an AC voltage.…”

Section: Introductionmentioning

confidence: 99%

Nanoscale Charge Accumulation and Its Effect on Carrier Dynamics in Tri-cation Perovskite Structures

Toth

Hailegnaw

Richheimer

et al. 2020

ACS Appl. Mater. Interfaces

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Nanoscale investigations by scanning probe microscopy have provided major contributions to the rapid development of organic–inorganic halide perovskites (OIHP) as optoelectronic devices. Further improvement of device level properties requires a deeper understanding of the performance-limiting mechanisms such as ion migration, phase segregation, and their effects on charge extraction both at the nano- and macroscale. Here, we have studied the dynamic electrical response of Cs 0.05 (FA 0.83 MA 0.17 ) 0.95 PbI 3– x Br x perovskite structures by employing conventional and microsecond time-resolved open-loop Kelvin probe force microscopy (KPFM). Our results indicate strong negative charge carrier trapping upon illumination and very slow (>1 s) relaxation of charges at the grain boundaries. The fast electronic recombination and transport dynamics on the microsecond scale probed by time-resolved open-loop KPFM show diffusion of charge carriers toward grain boundaries and indicate locally higher recombination rates because of intrinsic compositional heterogeneity. The nanoscale electrostatic effects revealed are summarized in a collective model for mixed-halide CsFAMA. Results on multilayer solar cell structures draw direct relations between nanoscale ionic transport, charge accumulation, recombination properties, and the final device performance. Our findings extend the current understanding of complex charge carrier dynamics in stable multication OIHP structures.

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“…In addition, when forming thinner films by, for example, the chemical etching of multilayer graphite, it becomes increasingly difficult to evaluate the characteristics in the c -axis direction, and the method developed in this study is expected to play a key role. Analysis of dynamics by time-resolved measurement may give important information. , …”

Section: Resultsmentioning

confidence: 99%

“…Analysis of dynamics by timeresolved measurement may give important information. 45,46 ■ CONCLUSION We performed measurements by MP-STP on a high-quality 2.7 μm thick graphite film with a large area fabricated by the PP method. In addition to the measurement of ρ ab over an abplane without wrinkles, MP-STP measurement over a cross section perpendicular to the ab-plane to acquire ρ c along the caxis was successfully achieved for the first time.…”

Section: ■ Introductionmentioning

confidence: 99%

Ultimate High Conductivity of Multilayer Graphene Examined by Multiprobe Scanning Tunneling Potentiometry on Artificially Grown High-Quality Graphite Thin Film

Mogi

Bamba

Murakami

et al. 2019

ACS Appl. Electron. Mater.

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With the discovery of graphene, the excellent characteristics of graphite (multilayer graphene), such as high thermal and electric conductivities, heat resistance, and chemical stability, have also been attracting considerable attention again. However, the production of a large-area (>0.1 × 0.1 m 2 ) graphite thin film with uniformly high electric conductivity, which will be indispensable in industrial applications, has been difficult because of its breakage occurring during the growth process. Recently, we have succeeded, for the first time, in growing large-area highquality graphite films with thicknesses from ∼0.5 to ∼3 μm by an industrial method, providing a fundamental platform for examining and utilizing the intrinsic and ultimate characteristics of such a material. Here, as a step toward realizing such efforts, we performed microscopic measurements of electric conductivity by the method of multiprobe scanning tunneling potentiometry we have developed. Using the resistivity along the c-axis, ρ c = 1.72 ± 0.04 mΩ•m, which was directly measured for the first time, we determined the resistivity in the abplane, ρ ab , to be 0.30 ± 0.01 μΩ•m, indicating that the conductance of the graphite thin film we grew is about 1.3 times the previous highest reported value for the highest grade single-crystal natural graphite with an ideal structure without grain boundaries or wrinkles (0.38 μΩ•m). Both the advantage of multilayer graphene, which is considered to reduce the effect of grain boundaries on conductance, and the decrease in conductance as an effect of wrinkles were directly evaluated.

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Externally triggerable optical pump-probe scanning tunneling microscopy

Cited by 9 publications

References 29 publications

Subcycle Transient Scanning Tunneling Spectroscopy with Visualization of Enhanced Terahertz Near Field

Subcycle Transient Scanning Tunneling Spectroscopy with Visualization of Enhanced Terahertz Near Field

Nanoscale Charge Accumulation and Its Effect on Carrier Dynamics in Tri-cation Perovskite Structures

Ultimate High Conductivity of Multilayer Graphene Examined by Multiprobe Scanning Tunneling Potentiometry on Artificially Grown High-Quality Graphite Thin Film

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