Efficient time-resolved surface/interface-specific electronic spectroscopy for surface/interface is crucial for understandings of dynamics of charges at surfaces and interfaces for energy conversion, catalysis, and photosynthesis.Here we developed a novel technique for surface/interface-specific broadband electronic sum frequency generation (ESFG). The broadband ESFG was based on a stable two-stage BiB3O6(BIBO) crystal-based optical parametric amplifier, in which generates a strong broadband short-wave IR (SWIR) from 1200 nm to 2400 nm.We further developed time-resolved broadband ESFG techniques to investigate structure and dynamics of charges at oxidized p-type GaAs (100) semiconductor surfaces, as an example. Two surface states inside the bandgap of the GaAs are revealed by both the steady-state and transient spectra. The kinetic processes at the GaAs surface after photoexcitation include the build-up of the space photo-voltage and the population and recombination of the surface states. The build-up of space photo-voltage occurs with a rate of 0.56 ± 0.07 ps-1, while the population rate of the surface states exhibits a two-bodybehavior witha rate constant of (0.012 ±0.002)*1012s-1×cm2. The photo-generated electron-hole pairs near the surface recombine with a rate of 0.002 ±0.0002 ps-1for the oxidized p-type GaAs (100). All the methodologies developedhereare readily applied to not only classical inorganic semiconductors surfaces and their interfaces with other materials, but also organic semiconductor surfaces, buried interfaces, and hybrid interfaces.

Charge dynamics at surfaces and interfaces with the development of time-resolved electronic sum frequency generation

2019 Fall National Meeting

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