Approaches Toward Chemically Prepared Multiple Quantum Well Structures

Abstract

An enhanced thermoelectric figure of merit, ZT, has been predicted for Bi₂ Te₃ in the form of 2-dimensional quantum wells. A new approach to making multiple quantum well (MQW) structures for thermoelectric applications utilizing a chemical intercalation technique is proposed and investigated. It is proposed that by starting from Li intercalated Bi₂ Te₃ and Bi₂ Se₃, the layers of these materials can be separated by chemical means. The layers of Bi₂ Te₃ or Bi₂ Se₃ can then be restacked, by self-assembly, forming a non-periodic array of quantum wells. These chemically prepared MQWs are characterized by X-ray diffraction, SEM (scanning electron microscopy) and TEM (transmission electron microscopy) at various stages in the sample preparation to assess the degree to which the actual samples match the proposal. Experimental measurements of the Seebeck coefficient ( S) and the electrical conductivity (σ) were performed over a range of temperatures for the initial bulk materials. It is found that some of the steps in the proposed fabrication have been achieved but still much improvement is needed before any practical thermoelectric 2D-system can be provided.