Title

Variations In The Conductive And Superconductive Properties Of {[tise2](l)[nbse2](m)}(n) Superlattices As A Function Of Superlattice Structure

Document Type

Article

Publication Date

10-1-2000

Publication Title

Chemistry Of Materials

Department

Physics

Abstract

An extensive set of {[TiSe2](l)[NbSe2](m)}(n) superlattices has been prepared through controlled annealing of elementally modulated reactants. Electrical conductances were measured from 1.5 K to room temperature. The room temperature conductances are linearly dependent on the number (m) of NbSe2 layers per repeat layer, and independent of the number (I) of semimetallic TiSe2 layers per repeat layer, suggesting that the electronic transport is dominated by the metallic NbSe2 layers. For small I, a positive temperature coefficient of resistance (TCR) is observed, indicative of normal metallic behavior. in general, increasing I reduces the TCR, and for smaller m, the TCR becomes negative at larger I. These samples exhibit a rootT temperature dependence to the resistivity variation at low temperatures, characteristic of both weak localization and electron-electron interaction effects for three-dimensional electron flow in strongly disordered systems. Superconducting critical temperatures were also observed to depend strongly on the superlattice structure. A thickness effect is observed in which the transition temperature is decreased as the number of superconducting NbSe2 layers within a repeat layer is reduced. For fixed m, the transition temperature is also reduced as the number of intervening TiSe2 layers is increased, indicating that interlayer coupling is also important. The domained structure of the samples is evident in an unusual I-V behavior observed in the temperature range of the superconducting transition. We interpret this behavior in terms of a simple model based on a patchwork of superconducting domains embedded in normal metal regions.

Volume

12

Issue

10

pp.

2894-2901

ISSN

0897-4756