Scanning tunneling microscopy investigations of the local electronic and structural effects of iron substitution in tantalum disulfide

Abstract

The microscopic structural and electronic properties of the charge density wave (CDW) phases in a series of iron-substituted tantalum disulfide materials, Fe{sub x}Ta{sub 1{minus}x}S{sub 2}, have been characterized with the use of scanning tunneling microscopy (STM). On average, the incommensurate CDW phase exhibits a regular hexagonal superlattice for x(Fe) {<=} 0.02. At the atomic level, however, analysis of real-space STM images shows that there are well-defined defects in this CDW structure. The frequency and size of the defects depend directly on the concentration of iron. These results resolve the source of differences between STM and previous diffraction studies of metal-substituted tantalum disulfide and also indicate that above a critical concentration of iron the properties of the CDW phase in these materials change significantly. The origin of this critical concentration is discussed.