p-type Bi2Se3 for topological insulator and low temperature thermoelectric applications

TL;DR

This paper reports the successful synthesis of p-type Bi2Se3 single crystals with enhanced thermoelectric properties and potential for topological insulator applications, achieved through Ca substitution and detailed defect analysis.

Contribution

It introduces a method to induce p-type behavior in Bi2Se3 via Ca doping and characterizes its thermoelectric and topological properties.

Findings

P-type Bi2Se3 exhibits a Seebeck coefficient of +180 μV/K at room temperature.

A giant Seebeck peak of +120 μV/K at 7 K was observed, indicating high thermoelectric power at low temperatures.

The Fermi level is lowered into the valence band by about 400 meV in Ca-doped Bi2Se3.

Abstract

The growth and elementary properties of p-type Bi2Se3 single crystals are reported. Based on a hypothesis about the defect chemistry of Bi2Se3, the p-type behavior has been induced through low level substitutions (1 percent or less) of Ca for Bi. Scanning tunneling microscopy is employed to image the defects and establish their charge. Tunneling and angle resolved photoemission spectra show that the Fermi level has been lowered into the valence band by about 400 meV in Bi1.98Ca0.02Se3 relative to the n-type material. p-type single crystals with ab plane Seebeck coefficients of +180 microVK-1 at room temperature are reported. These crystals show a giant anomalous peak in the Seebeck coefficient at low temperatures, reaching +120 microVK-1 at 7 K, giving them a high thermoelectric power factor at low temperatures. In addition to its interesting thermoelectric properties, p-type Bi2Se3 is of substantial interest for studies of technologies and phenomena proposed for topological insulators.