We have used scanning tunneling microscopy working at 4.2 K to study the transition metal dichalcogenide 1T-TaSe2. The charge density wave (CDW) superstructure (131/2α0×131/2α0) and atomic modulation are well resolved, as well as the associated CDW energy gap. In particular we used high purity iron as tip material and demonstrated clearly the existence of single electron tunnel-ing (so-called Coulomb blocade) effects, further experiments with stainless steel tips also confirmed this observation. It is pointed out that during STM/STS studies tips covered with oxides are very likely to display Coulomb blocade effects due to their small capacitance. Therefore, extra cautious are needed when analyzing spectroscopic features in the area that could be affected by Coulomb blocade effects. At the mean time, high quality scanning images can still be regularly obtained through reso-nant tunneling process.
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