In-plane Topological p-n Junction in the Three-Dimensional Topological Insulator Bi$_{2-x}$Sb$_x$Te$_{3-y}$Se$_y$

TL;DR

This paper reports the fabrication and experimental observation of an in-plane topological p-n junction on a 3D topological insulator surface, demonstrating controllable spin and charge transport with potential applications in spintronics.

Contribution

It introduces a novel method to create and control in-plane topological p-n junctions on 3D topological insulator surfaces using chemical potential tuning.

Findings

Successful fabrication of in-plane TPNJ on BiSbTeSe thin films.

Electrical transport changes dramatically at the TPNJ.

Controlled TPNJ on both top and bottom surfaces via back-gate voltage.

Abstract

A topological p-n junction (TPNJ) is an important concept to control spin and charge transport on a surface of three dimensional topological insulators (3D-TIs). Here we report successful fabrication of such TPNJ on a surface of 3D-TI Bi$_{2-x}$Sb$_x$Te$_{3-y}$Se$_y$ thin films and experimental observation of the electrical transport. By tuning the chemical potential of n-type topological Dirac surface of BSTS on its top half by employing tetrafluoro-7,7,8,8-tetracyanoquinodimethane as an organic acceptor molecule, a half surface can be converted to p-type with leaving the other half side as the opposite n-type, and consequently TPNJ can be created. By sweeping the back-gate voltage in the field effect transistor structure, the TPNJ was controlled both on the bottom and the top surfaces. A dramatic change in electrical transport observed at the TPNJ on 3D-TI thin films promises novel spin and charge transport of 3D-TIs for future spintronics.