Development of interface-/surface-specific two-dimensional electronic spectroscopy

Deng, Gang-Hua; Wei, Qianshun; Qian, Yue; Zhang, Tong; Leng, Xuan; Rao, Yi

doi:10.1063/5.0019564

Cited by 10 publications

(23 citation statements)

References 140 publications

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“…The BOPA was based on a type I BiB 3 O 6 crystal. In our early work, , we presented a two-stage BOPA for the broadband SWIR source, in which a white light continuum was generated as a seed pulse. The two-stage BOPA caused stability issues due to the non-trivial continuum light.…”

Section: Experimental Methodsmentioning

confidence: 99%

Spectral Phase Measurements of Heterodyne Detection in Interfacial Broadband Electronic Spectroscopy

et al. 2022

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A spectral phase is vital to retrieve both the real and imaginary parts of both second-order vibrational and electronic sum frequency generation spectra. Despite recent efforts, phase measurements in electronic spectra at interfaces are lacking. In particular, references are not well established for frequency-dependent spectral phases in interfacial electronic spectroscopy. In this work, we present broadband heterodyne detection (HD) of interfacial electronic spectroscopy for spectral phases of references. Such a broadband HD method was based upon a broadband short-wave IR laser source from 1100 to 2200 nm. A collinear geometry method was adopted for passive phase stability. We further compared often-used reference samples, including gold (Au) thin films, silver (Ag) thin films, p-type GaP (100), p-type GaAs (100), as well as left-handed and right-handed z-cut α-quartz crystals. The phases of the second-order susceptibilities for Ag thin films, the GaP crystal, the GaAs crystal, and the quartz crystals are independent of frequency from 630 to 730 nm. More importantly, it was found that the often-used Au thin film in the literature is not a good phase reference for frequency-dependent phases.

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Section: Experimental Methodsmentioning

confidence: 99%

Spectral Phase Measurements of Heterodyne Detection in Interfacial Broadband Electronic Spectroscopy

et al. 2022

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“…The spectra of the ps 800 nm and the SWIR are shown in Figure S1. A detailed description of design and implementation of the BOPA were reported in our previous work. ,, The remaining portion of 0.5 mJ was used to generate a pump pulse of 400 nm by a beta-barium borate (BBO) crystal.…”

Section: Methodsmentioning

confidence: 99%

“…They found that competing charge separation processes existed in the GaAs/CuPc interface and that the space-charge field of GaAs slows down the hole injection to CuPc. Our early work demonstrated surface dynamics for p -type GaAs (100) with the development of time-resolved broadband ESFG. ,, TR-ESFG could provide time-resolved spectral information about surface structures as well as charge transfer occurring at semiconductor surfaces.…”

Section: Introductionmentioning

confidence: 97%

Photoinduced Surface Electric Fields and Surface Population Dynamics of GaP(100) Photoelectrodes

et al. 2022

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Gallium phosphide (GaP) photoelectrodes have received remarkable focus due to their applications in photocatalysis and photoelectrocatalysis of CO 2 reduction reactions. Understanding the dynamical mechanisms of surfaces of photoelectrodes is essential in improving their working efficiencies in any application. However, knowledge of photoinduced surface dynamics of these materials is lacking. Here, we investigate surface dynamics of n-type and p-type GaP(100) semiconductors by utilizing time-resolved electronic sum frequency generation (TR-ESFG). Transient ESFG spectra showed that four surface states in both n-and p-type GaP(100) were involved in subsequent kinetics. Transient spectral signatures of the surface states showed that photoexcited electrons move toward the surface regions for p-type GaP, while photoexcited holes move to the surface regions for n-type GaP. These carriers first build up surface electric fields, resulting in fluence-dependent band flattening. The buildup rates of the surface electric fields were found to be on the order of 2.86 ± 0.30 ps −1 for n-type and 2.50 ± 0.25 ps −1 for p-type. Subsequently, a relatively slow process occurs, being attributed to population dynamics of surface states dependent upon applied fluences. We found that surface population behaves as a bimolecular process with rates of 0.020 ± 0.002 cm 2 s −1 for n-type and 0.035 ± 0.002 cm 2 s −1 for p-type GaP. The four surface states, shallow and deep for both n-and p-type GaP(100), were found to be involved in both surface electric fields and surface carrier populations, contrary to previous hypotheses. Our time-resolved surface-specific approach provides unique information on surface dynamical behaviors of photoelectrodes under ambient conditions.

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“…A detailed description of steady-state ESFG experiments has been reported previously. ,, Briefly, a fundamental light centered at 797 nm from a 1 kHz Ti:sapphire amplifier system (UpTek Solutions) was used. The output energy of the laser was 4 mJ per pulse with a pulse duration of 100 fs.…”

Section: Experimental Sectionmentioning

confidence: 99%

“…A major portion of 2.0 mJ was passed through an etalon to generate a picosecond pulse of 8 cm –1 . A small portion of 1.5 mJ was used to generate a shortwave IR (SWIR) pulse from a home-built broadband optical parametric amplifier (BOPA). ,, The remaining fundamental pulse of 0.5 mJ was doubly converted with a beta-barium borate (BBO) crystal into 400 nm as a pump pulse. The time delay between the picosecond pulse and the SWIR was controlled by a motorized translation stage (Klinger).…”

Section: Experimental Sectionmentioning

confidence: 99%

Surface States for Photoelectrodes of Gallium Phosphide (GaP) with Surface-Specific Electronic Spectra and Phase Measurements

et al. 2022

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Gallium phosphide (GaP) photoelectrodes have received tremendous attention owing to their applications in photocatalysis and photoelectrocatalytic reduction of CO 2 . Surface electronic states of GaP are important in such catalysis applications. However, knowledge of surface states of GaP under ambient conditions is lacking. Here, we combined azimuth-dependent electronic sum-frequency generation (ESFG) spectroscopy with phase measurements to investigate the surface states for n-type and p-type GaP(100) semiconductors. ESFG spectroscopic studies enabled us to identify three surface states of the GaP crystals under ambient conditions. These experiments have also shown that all of the spectral features come from surface contributions for both the n-type and p-type GaP(100) crystals and that both surface dipoles and surface charges were responsible for the electronic transitions of isotropic and anisotropic components. Combined with azimuth-dependent phase measurements, surface charges were found to account for the isotropic surface ESFG components: negative for n-type and positive for p-type GaP(100). Finally, we conducted a thorough theoretical analysis of surface and bulk contributions for azimuth-dependent ESFG responses. With these spectral and phase signatures, we have further quantified surface and bulk contributions along different orientations for the n-type and p-type GaP(100) crystals.

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Development of interface-/surface-specific two-dimensional electronic spectroscopy

Cited by 10 publications

References 140 publications

Spectral Phase Measurements of Heterodyne Detection in Interfacial Broadband Electronic Spectroscopy

Spectral Phase Measurements of Heterodyne Detection in Interfacial Broadband Electronic Spectroscopy

Photoinduced Surface Electric Fields and Surface Population Dynamics of GaP(100) Photoelectrodes

Surface States for Photoelectrodes of Gallium Phosphide (GaP) with Surface-Specific Electronic Spectra and Phase Measurements

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