Structural Modulation in LaO0.9F0.1BiSe2 Single Crystals Revealed by Scanning Tunneling Microscopy/Spectroscopy

We present scanning tunneling microscopy and spectroscopy measurements on a cleaved surface of the LaO0.9F0.1BiSe2 single crystals. Tunneling spectra show a finite local density of states at E F, which is consistent with metallic conductivity in bulk. In addition, the existence of the supermodulation running along the diagonal directions of Bi square lattice was revealed. The period of the supermodulation was about 3 to 5 times the length of the lattice constant. This period is close to that observed in LaO0.5F0.5BiSe2.