Detection of atomic surface structure on NbSe2 and NbSe3 at 77 and 4.2 K using scanning tunneling microscopy

Abstract

Scanning tunneling microscopy (STM) studies have been performed on NbSe₂ and NbSe₃ at 77 and 4.2 K. The surface atomic structure has been clearly resolved, but evidence of charge‐density wave (CDW) modulation has only been observed at 4.2 K in NbSe₃. CDW’s exist in NbSe₂ at 4.2 K and in NbSe₃ at 77 K, but the CDW amplitude is either too small or is screened by the remaining conduction electrons. The linear chain structure in NbSe₃ has been clearly resolved and the STM profiles are dominated by the heights and effective charges of the surface Se atoms. Improved sensitivity and resolution will be required to study any details of the CDW structure in both compounds.