Metal-nonmetal transition in LixCoO2 thin film and thermopower enhancement at high Li concentration

TL;DR

This study explores the transport properties of LixCoO2 thin films, revealing a metal-nonmetal transition at high lithium content and significant thermopower enhancement at low temperatures, indicating complex electronic correlations.

Contribution

It provides new insights into the transport behavior and thermopower enhancement in LixCoO2 thin films at high Li concentrations, highlighting a metal-nonmetal transition and crossover phenomena.

Findings

Resistivity of thin films is much lower than bulk polycrystals.

Metal-nonmetal transition occurs at x ≈ 0.8.

Seebeck coefficient peaks at ~120 μV/K around 140 K for x=0.87.

Abstract

We investigate the transport properties of LixCoO2 thin films whose resistivities are nearly an order of magnitude lower than those of the bulk polycrystals. A metal-nonmetal transition occurs at ~0.8 in a biphasic domain, and the Seebeck coefficient (S) is drastically increased at ~140 K (= T*) with increasing the Li concentration to show a peak of magnitude ~120 \muV/K in the S-T curve of x = 0.87. We show that T* corresponds to a crossover temperature in the conduction, most likely reflecting the correlation-induced temperature dependence in the low-energy excitations.