Thermopower analysis of the electronic structure around metal-insulator transition in V1-xWxO2

TL;DR

This study investigates the electronic structure changes in W-doped VO2 across the metal-insulator transition using thermopower measurements, revealing a correlation between thermopower and transition temperature and insights into the density of states.

Contribution

It provides new thermopower data on W-doped VO2, linking thermopower behavior to electronic structure and doping levels across the transition.

Findings

Thermopower increases significantly at the MI transition.

Transition temperature decreases linearly with W concentration.

Thermopower at high T remains constant, indicating metallic behavior.

Abstract

Electronic structure across the metal-insulator (MI) transition of electron-doped V1-xWxO2 epitaxial films (x = 0-0.06) grown on alfa-Al2O3 substrates was studied by means of thermopower (S) measurements. Significant increase of |S|-values accompanied by MI transition was observed, and the transition temperatures of S (TS) decreased with x in good linear relation with MI transition temperatures. |S| values of V1-xWxO2 films at T > TS were constant at low values of 23 microV K-1 independently of x, which reflects a metallic electronic structure, whereas, those at T < TS almost linearly decreased with logarithmic W-concentrations. The gradient of -213 microV K-1 agrees well with -kB/e*ln10 (-198 microV K-1), suggesting that V1-xWxO2 films have insulating electronic structures with a parabolic density of state around the conduction band bottom.