Picosecond surface restricted transient grating studies of carrier reaction dynamics at n-GaAs(100) interfaces

Abstract

The surface restricted transient grating technique has been found to be sensitive to the Fermi level pinning surface states at the atomic interface of the native oxide layer of (100) GaAs. The sensitivity to these states is better than 10-4 of a monolayer. The grating signal associated with the surface states is eliminated by photoinduced removal of the oxide layer and hole transfer to Se-2 ions adsorbed to the surface. These results support the assignment of the signal to electronic factors associated with surface state species. The use of space charge field focusing of hole carriers to the surface has enabled a discrimination of the hole carrier reaction dynamics from those of the electron at the surface. In situ studies of interfacial hole transfer to Se-2 ions present at liquid junctions found the hole transfer time to be less than 30 ps. The selective quenching of the hole carrier through interfacial charge transfer has found that the hole carrier contributes to the optical dispersion in the 1 f-l region to approximately the same extent as the electron.

Generation and observation of GHz ultrasonic waves on liquid surfaces and a liquid/liquid interface by transient reflecting grating method

“…[22][23][24][25][26][27][28][29][30][31][32][33] Two temporally coincident laser pulses ͑pump pulses͒ with the same wavelength produce optical interference fringes on and under the sample surface. These optical fringes cause spatial modulations of the refractive index and surface displacement.…”

“…[23][24][25][26] Fayer and co-workers 27,28 and Nelson and co-workers 28 presented detailed theoretical analysis of the method. This technique was used to generate and detect GHz surface acoustic waves successfully.…”

“…[29][30][31][32][33] Some chemical or physical applications were also made for measurements of ultrafast carrier dynamics. [34][35][36][37][38] This method has advantages of providing noncontact, nondestructive, and interface-selective measurements, and high temporal resolution. Moreover, it can be applied to various types of samples because it utilizes nonradiative relaxation processes.…”

Effects of metal ion chemisorption on gallium arsenide surface recombination: picosecond luminescence decay measurements

“…This observation is fully consistent with prior measurements indicating the significant adsorption of electroactive species on surfaces immersed in KOHSe-/2-(aq) solutions and is also consistent with the unique stabilization and the flat-band shift of GaAs in contact with the KOHSe-I2-(aq) electrolyte system.22 ' The Smin values observed herein are also consistent with the picosecond optical grating measurements of hole transfer at the n-GaAs/KOHSe-/2-(aq) electrolyte. 32 The optical grating studies were performed under low level injection, and the band bending therefore rapidly confined the carriers to a thin region near the surface. Assuming a 10-A-thick surface region, a value of Smin = IO5 cm s-* would correspond to a transfer time of T = IO-' cm/lOS cm s-l = 1 ps, which is in accord with the optical grating studies.32 The present work is thus in agreement with prior experimental and theoretical expectations for the system of interest.…”

PHOTOTHERMAL APPLICATIONS OF LASERS: Study of Fast and Ultrafast Photothermal Phenomena at Metal-Liquid Interfaces

“…Over the past decade, temporal resolution in observing PT/PA phenomena has been improved with the help of ultrafast laser-based technologies, such as transient grating (TG) spectroscopy (6,7,11,(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37) and transient reflectivity (TR) spectroscopy (9,(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48). Measurements of TGs and transient lenses (49)(50)(51)(52) have been used successfully to investigate heat generation in liquid solutions and transparent solids.…”