We investigated the photon energy dependence of the P $2p$ core-level photoemission intensity for clean cleaved InP(110) and for cleaved InP(110) covered with Al. The results can be explained in terms of an extended x-ray-absorption fine structure (EXAFS) modulation, in spite of the limited angular acceptance of the photoelectron analyzer. Applying conventional EXAFS analysis procedures and using theoretical $L$-edge backscattering-phase-function data of McKale et al. plus Teo and Lee absorber phase function, we derive bond distances for InP(110) in excellent agreement with the low-energy electron diffraction results. The data for Al-covered surfaces are consistent with the known exchange reaction between Al and In. These results suggest that the photoemission EXAFS technique can be extended to ordered surfaces and interfaces and core levels of atoms in the adsorbent can be used for surface studies.

• Received 21 March 1988

DOI:https://doi.org/10.1103/PhysRevB.38.1566