  We utilized X-ray photoemission electron microscopy (XPEEM) and X-ray
photoelectron spectroscopy (XPS) to investigate the crystal surface of Weyl
semimetal NbAs. XPEEM images present white and black contrast in both the Nb 3d
and As 3d core level spectra. Surface-sensitive XPS spectra indicate that the
entire surface of the sample contains both surface states of Nb 3d and As 3d,
in form of oxides, and bulk states of NbAs. Estimated atomic percentage values
nNb/nAs suggest that the surface is Nb-rich and asymmetric for white and black
areas.
