Investigation of the optical reflectivity of misfit layer compounds

(MS)_nTS₂(T=Ta, Nb; M=Sn, Pb, Sm, Tb, La; 1.08<n<1.23)

authored by

C. H. Ruscher, C. Haas, S. Van Smaalen, G. A. Wiegers

Abstract

The room temperature reflectivity of the misfit layer compounds (MS) _nTS₂ (T=Nb, Ta) is investigated in the spectral range 1000-20000 cm ^-1. The reflectivity for the E-vector parallel to the (001) planes and the incident light along (001) is dominated by the charge carrier response. This part of the spectra can be described using the Drude formula with the plasma frequency given by omega p=(Ne²/ epsilon ₀ epsilon _infinitym*)^0.5 (N=charge carrier concentration, m*=effective mass, epsilon _infinity= high-frequency dielectric constant). For compounds with M=Sn, Pb the number of charge carriers is equal to that of the parent compound TS₂. The observed anisotropy in the (001) plane is rather small and can be related to small differences in the effective masses (m₍₀₁₀₎^*/ m₍₁₀₀₎^* approximately=0.98). This effect is attributed to the orthorhombic distortion of the (TS₂) sublattice. For compounds with M=La, Sm, Tb, electron donation is indicated and the plasma frequency is determined by about 0.5, 0.2, 0.25 holes per T ion, respectively, in a single (TS₂)-related conduction band.

External Organisation(s)

University of Groningen

Type

Article

Journal

Journal of Physics: Condensed Matter

Volume

6

Pages

2117-2128

No. of pages

12

ISSN

0953-8984

Publication date

15.11.1993

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

General Materials Science, Condensed Matter Physics

Electronic version(s)

https://doi.org/10.1088/0953-8984/6/10/029 (Access: Closed)