Adsorption/desorption kinetics of H2O on GaAs(100) measured by photoreflectance

Abstract

The mechanism of H2O adsorption on GaAs(100) has been elucidated by an adaptation of the photoreflectance (PR) technique for surface kinetic measurements. Being an optical method, PR is especially well-suited for probing weakly bonded adsorption systems where the pressures required for significant interaction (≳10−5 Torr) preclude the use of traditional electron or ion spectroscopies. H2O adsorbs through a physisorbed state. This species can desorb or react to a chemisorbed form, which in turn can desorb. Both the physisorbed and chemisorbed species are undissociated. We interpret exceptionally low values for the prefactors associated with the chemisorbed state in terms of an adsorbate-induced surface reconstruction.

Adsorption and dissociation of H2O on the Ga-rich GaAs(001)-(4×2) surface: DFT and DFT-D computations with a Ga7As8H11 cluster model

“…As presented in the section of Introduction, the experimental results are different due to different GaAs surfaces and experimental conditions [6][7][8][9][10][11][12][13][14]. Chung et al [13] studied the reaction mechanism of the H 2 O molecule with the GaAs(1 0 0)-(4 Â 2) surface.…”

“…The corresponding adsorption and decomposition mechanisms were elucidated experimentally and theoretically [4,5]. As to the interactions of H 2 O with the GaAs surfaces, different mechanisms were obtained with different GaAs surfaces and experimental conditions [6][7][8][9][10][11][12][13][14]. The dissociation of H 2 O on the GaAs surface was found due to the formation of the Ga-O bond [7,[11][12][13][14].…”

Defect engineering in semiconducting oxides: Control of ZnO surface potential via temperature and oxygen pressure

“…The analytical method described here tacitly assumes that V S and C are linearly related, an assumption that has been justified elsewhere . Thus, if V S has been measured by this method at a given value of T , it is not necessary to replicate the entire intensity‐dependent set of experiments when changing P at the same T .…”

“…This work used a small turbomolecularly pumped ultrahigh vacuum (UHV) chamber designed as described previously with a base pressure of roughly 2 × 10 −10 Torr. The optical cube chamber body was equipped with fused‐silica optical ports, an inlet and handling system for O 2 , ionization and thermocouple pressure gauges, and an electrical feedthrough for specimen support, heating, and temperature measurement.…”

Semiconductor surface diffusion: Nonthermal effects of photon illumination

“…The optical components and setup closely resembled those of work we have previously published, 17 with the variable-wavelength probe beam at a 45°angle of incidence. The perturbing light impinged at normal incidence from the He-Ne laser referred to above, but with a mechanical chopper ͑400 Hz͒ placed in the beam for phase-sensitive detection of the induced reflectance change.…”