Core-level X-ray photoemission spectral shift through the successive phase transitions in layered TlInS2

Temperature-dependent change in core-level electronic structures of the layered semiconductor-ferroelectric TlInS2 with incommensurate phase has been investigated by means of X-ray photoemission spectroscopy. The temperature dependence of the relative peak position for each core level (Tl 4f, In 3d and S 2p) is found to differ very much in the regions bordering each other at the normal-incommensurate phase transition point of 218 K. The obtained data suggest that the charge distribution in TlInS2 dramatically changes upon passing from the normal phase (T>218 K) to the spatially modulated incommensurate phase (T<218 K).