Optical and electrical studies of Ti- and Ta-dichalcogenides: Plasmons

Abstract

We have measured the room temperature reflectance of the Ti and (1T) Ta dichalcogenides as well as TiSe₂ alloyed with TaSe₂. Two types of carriers with different relaxation times are required to account for the observed plasma reflection. Both of these plasma frequencies in TiSe₂ increase with increasing Ta content, suggesting they are associated with electrons. The resistivity of these alloys falls on decreasing the temperature with a knee occurring at a temperature where electron diffraction shows the appearance of a superlattice. This knee diminishes and moves to lower temperature with increasing carrier concentration.