Synopsis: Making room for holes

The ability to hole-dope Bi2Se3 is an important step toward exploring the thermoelectric properties of this material.
Synopsis figure
Illustration: Y. S. Hor et al., Phys. Rev. B (2009)

(Bi,Sb)2(Te,Se)3 binary compounds have been extensively studied for their thermoelectric properties. Although primarily Bi2Te3 and also Bi2Se3 are more commonly used as thermoelectric materials, they have recently begun to attract attention due to the promise of hosting so-called topological surface states.

One of the major issues for both thermoelectric applications and fundamental research on topological phases in Bi2Se3 is creating a hole-doped variant of this material. Pure Bi2Se3 exhibits n-type behavior due to the presence of selenium vacancies that act as electron donors, but hole-doping is much more difficult.

Writing in Physical Review B, Yew San Hor and collaborators from Princeton University report that they have managed to dope holes into Bi2Se3 by substituting calcium for bismuth. Scanning-tunneling microscopy reveals that the calcium donates holes that compensate the electrons created by the selenium vacancies.

Angle-resolved photoemission spectroscopy in turn reveals that the hole-doping substantially lowers the Fermi level in Bi2Se3 with respect to that of pure Bi2Se3. In order to access topological surface states, it is necessary to be able to tune the Fermi level, which should be possible in this material. The hole-doped material also exhibits intriguing transport anomalies at low temperatures that are currently not understood. – Alex Klironomos


More Features »


More Announcements »

Subject Areas

Materials Science

Previous Synopsis

Next Synopsis

Nuclear Physics

Signs of a critical point

Read More »

Related Articles

Synopsis: Crumpled Graphene

Synopsis: Crumpled Graphene

The crumpling of graphene sheets explains a “soft spot” in the material’s mechanical response. Read More »

Synopsis: Powering up Magnetization
Materials Science

Synopsis: Powering up Magnetization

New theoretical work identifies a dynamic form of multiferroic behavior, in which a time-varying electric polarization induces magnetization in a material. Read More »

Viewpoint: How to Make Devices with Weyl Materials
Materials Science

Viewpoint: How to Make Devices with Weyl Materials

Weyl semimetals could be used to build a range of electronic devices, from superlenses for scanning tunneling microscopes to transistors. Read More »

More Articles