Modulated STM images of ultrathin MoSe2 films grown on MoS2(0001) studied by STM/STS

The MoSe2/MoS2 system is investigated by scanning tunneling microscope (STM ) and by its spectroscopic mode, scanning tunneling spectroscopy (STS). STM images show a hexagonal wagon-wheel-like pattern, which is made of bright lines and dark triangles. High-resolution STM images show that the bright l ine consists of twin lines separated by about 1 nm and that the hexagonal p attern is often skewed. These features are not explained by the simple moir e effect due to the lattice mismatch, between the overlayer and the substra te materials. The STS spectra show that the bright area results mainly from electron waves derived from chalcogen orbitals running parallel to the int erface between MoSe2 and MoS2 layers. A mechanism of the pattern formation is proposed, in which scattered electron waves produce the bright wagon-whe el-like pattern. [S0163-1829(99)02916-1].