Strained and Unstrained Bi(1-x)Sb(x) Superlattice Thermoelectrics

Abstract

The electronic band structure of artificially ordered superlattice alloys (SLA) of Bi and Sb, prepared by alternately depositing thin layers of Bi and Sb as a superlattice, could be modified from a semimetal to a semiconductor by changing the period of the superlattice. This new SLA opens a possibility to engineer an alloy material to get more desirable thermoelectric properties, because a thermal conductivity reduction, due to an increase in phonon scattering from the superlattice interfaces, is expected; certain electronic properties are altered at the same time. To check the performance of an in-plane Bi/BiSb cooling device, anisotropy in the films was investigated. Bi showed a strongly anisotropic and field-direction-dependent magneto-Seebeck effect. The magneto-transport properties of Bi(1-x)Sb(sub x) films and Bi/CdTe superlattices have been determined by applying the Quantitative Mobility Spectrum Analysis and multicarrier fitting to the magnetic-field-dependent resistivities and Hall coefficients, using algorithms which account for the strong anisotropy of the mobilities. Using the local density relativistic full-potential linear muffin-tin orbital method, we found that the internal displacement changes the Bi electronic structure from a metal to a semimetal and that an increase of the trigonal shear angle can lead to a semimetal-semiconductor transition in Bi. Post annealing of Bi films near its melting point improved the magnetoresistance ratios drastically, which can be ascribed to the electron mobility enhancement. The calculation of the electronic structure of Bi2Te3 suggested that the quasi-two dimensional crystal structure of Bi2Te3 gives a large, but finite, anisotropy in the effective mass which enhances the thermoelectric figure of merit.

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Document Details

Document Type
Technical Report
Publication Date
May 19, 2001
Accession Number
ADA390859

Entities

People

  • Antonio Divenere
  • Arthur J. Freeman
  • George K. Wong
  • J. B. Ketterson
  • Jerry R. Meyer

Organizations

  • Northwestern University

Tags

Communities of Interest

  • Advanced Electronics
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Band Structures
  • Crystal Lattices
  • Crystal Structure
  • Crystals
  • Diffraction
  • Electrical Conductivity
  • Electron Mobility
  • Energy Bands
  • Fermi Levels
  • Materials
  • Military Research
  • Phase Transformations
  • Semiconductors
  • Solid State Physics
  • Thermal Conductivity
  • Transport Properties
  • Two Dimensional

Fields of Study

  • Materials science

Readers

  • Materials Science and Engineering.
  • Quantum Dot Semiconductor Device Photonics and Graphene Optoelectronic Materials and THz Physics.

Technology Areas

  • Microelectronics
  • Microelectronics - Graphene
  • Space