High-resolution core level photoelectron spectroscopy on InP(110)

We investigate the lineshape of In4d and P2p core level emission spectra recorded with high spectral resolution on cleaved InP(110) surfaces for a wide range of photon energies. A curve fitting analysis with Voigt functions is used to decompose the spectra in surface and bulk core level emission lines. We find that an intrinsic broadening of approximately 250 meV limits the linewidth of the In4d and P2p emission components of both surface and bulk. We attribute the broadening to local band bending variations induced by surface inhomogeneities such as cleavage steps and atomic defects. Surface core level shifts of 320 meV for In4d and 305 meV for P2p are found, in excellent agreement with previously published data. The intensity of the surface components with respect to those of the bulk is found to deviate from the expectation based upon the electron escape depth due to photoelectron diffraction effects.