The interface of GaP(100) and H2O studied by photoemission and reflection anisotropy spectroscopy

摘要

We study the initial interaction of adsorbed H2O with P-rich and Ga-richGaP(100) surfaces. Atomically well defined surfaces are prepared bymetal-organic vapour phase epitaxy and transferred contamination-free toultra-high vacuum, where water is adsorbed at room temperature. Finally, thesurfaces are annealed in vapour phase ambient. During all steps, the impact onthe surface properties is monitored with in-situ reflection anisotropyspectroscopy (RAS). Photoelectron spectroscopy and low-energy electrondiffraction are applied for further in-system studies. After exposure up tosaturation of the RA spectra, the Ga-rich (2 x 4) surface reconstructionexhibits a sub-monolayer coverage in form of a mixture of molecularly anddissociatively adsorbed water. For the p(2 x 2)/c(4 x 2) P-rich surfacereconstruction, a new c(2 x 2) superstructure forms upon adsorption and theuptake of adsorbate is significantly reduced when compared to the Ga-richsurface. Our findings show that microscopic surface reconstructions of GaP(100)greatly impact the mechanism of initial interface formation with water, whichcould benefit the design of e.g. photoelectrochemical water splitting devices.