Superstructure formation and X-ray photoemission properties of the TlTiOPO4 surface

X-ray photoemission spectroscopy (XPS) measurements have been executed for TlTiOPO4 to elucidate the general features in the electronic structure of the KTiOPO4 family compounds. The peculiarities of the valence band structure have been discussed for the crystals. The persistence of core level binding energy differences O 1s-P 2p and O 1s-Ti 2p(3/2) has been detected in TlTiOPO4 and KTiOPO4, which relates well with the constancy of averaged P-O and Ti-O chemical bond lengths in this crystal family. The superstructure ordering of the TlTiOPO4 surface subjected to polishing and annealing has been detected by reflectance high energy electron diffraction (RHEED). From comparison of surface crystallographic properties of TlTiOPO4 and KTiOPO4, the most typical superstructure indices have been revealed.