Valence and core-level photoelectron spectroscopy studies of Fe2P$(10\bar{1}0)$: Effect of P segregation on the surface electronic structure

The effect of P segregation on the electronic structure of Fe2P has been studied by soft X-ray photoelectron spectroscopy (PES). As the Fe2P surface was sputtered by Ar+ ion (2 kV, 10 min), the amount of P atoms in the surface region was reduced. The amount of surface P atoms was further reduced by annealing the sputtered surface at elevated annealing temperatures up to about 400 °C, and it was increased by annealing at temperatures higher than 400 °C. It was deduced from the analyses of the P 2p core-level PES spectra that desorption of P atoms weakly bonded to the surface, which are thought to be formed through the sputtering process, proceeded when the surface was annealed at temperatures lower than 500 °C. On the other hand, it was also deduced from the PES study that the segregation of bulk P atoms toward the surface proceeded when the annealing temperature was higher than 300 °C. These two processes were competing at 300–500 °C, leading to the minimum amount of surface P atoms at approximately 400 °C. The PES spectra were measured after annealing the sputtered surface at various temperatures, and it was found that the stabilization of the 3d states of surface Fe atoms due to the bonding with surrounding P atoms was ineffective irrespective of the amount of P atoms on Fe2P.