In-plane topological p-n junction in the three-dimensional topological insulator Bi2−xSbxTe3−ySey

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 Bi2−xSbxTe3−ySey thin films and experimental observation of the electrical transport. By tuning the chemical potential of n-type topological Dirac surface of Bi2−xSbxTe3−ySey on its top half by using 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.

Thermoelectric properties of 3D topological insulator: Direct observation of topological surface and its gap opened states

“…1(a) and (b). The detailed band diagram required for interpretations of the TE properties was determined based on the quantum oscillations as well as the evolution of resistivity (ρ) as a function of temperature (T) in addition to the previous literatures as described later 31,32,34 . As schematically illustrated in Fig.…”

“…We also find g-TSDS in the limit of 4QL. Importantly, the grown single crystal BSTS thin films can beneficially be transferred to any other substrates under a damage-free condition 31,32 , and therefore physical parameters important for having intrinsic interpretations on the TE properties can be available by various measurements. The value of S for m-TSDS is found to be one order larger than that of conventional metals.…”

“…BSTS single crystal thin films with 1cm 2 large in size were grown on mica substrate with a catalystfree epitaxial physical vapor deposition (PVD) method using a dual-quartz system, which detail method was reported elsewhere 31,32 . A highly insulating Bi1.5Sd0.5Te1.7Se1.3 single crystal was used as a source material 33,34 , and the film thickness was controlled by the deposition time.…”

Optical manipulation of work function contrasts on metal thin films

“…Moreover, in special cases such as three-dimensional topological insulators, where the charge transport is desired to be only on the surface, creating in-plane WF contrasts is certainly critical. Very recently, an in-plane topological p-n junction has been created on a three-dimensional topological insulator, where one-half of the surface is chemically modified with the surface chemical potential tuned to result in a p-type zone, leaving the other half of the surface as n-type ( 11 ). With rather inadequate research on creating an in-plane contrast in the chemical potential or the electronic energy level of a material surface, the present work throws light on a new approach for localized modulation of WF and for in-plane charge transport simply by white light illumination.…”

Spintronic signatures of Klein tunneling in topological insulators

“…1(a) shows a schematic structure of the TI pn junction in a potentiometric measurement setup. The TI surface can be chemically doped into P or N-type, as demonstrated in multiple experiments [19,20] the source side that can swing it electrostatically to Ntype. The rest of the P-type TI surface is exposed and a ferromagnetic probe is placed on top of the exposed surface to monitor the voltage at different gate bias and angular orientations (the orientation can be altered by using multiple contacts at relative angles, as we discuss later).…”