INVESTIGATIONS OF ELECTRONIC-STRUCTURES OF DEFECTS INTRODUCED BY AR ION BOMBARDMENTS ON MOS2 BY SCANNING-TUNNELING-MICROSCOPY

We have investigated the defects introduced by Ar ion bombardment on cleaved MoS2 surface by scanning tunneling microscopy (STM). The resultant defects have been observed at room temperature as dark regions typically 6-8 nm in diameter and their contrast is found to depend on the sample bias voltage (SB). The high-temperature STM observations at 600 degrees C and 800 degrees C show a reduction of the diameter to 2-4 nm. Based on these experimental results it is concluded that the S atom complex produced at the defect site is partially negatively ionized and a depletion region of conduction electrons is produced around it. The observed lateral extent of the depletion region is in good agreement with that calculated from the repulsive Coulomb potential due to the negatively charged complex. The calculated screening length, however, disagrees with the observed size the dark region.