Platform for in-plane ZT measurement and Hall coefficient determination of thin films in a temperature range from 120 K
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edemann Völklein Institute for Microtechnologies, RheinMain University of Applied Sciences Wiesbaden, Ruesselsheim 65428, Germany
Heiko Reith Institute of Nanostructure and Solid State Physics, Universität Hamburg, Hamburg 20355, Germany; and Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Dresden 01171, Germany
Peter Woias Department of Microsystems Engineering–IMTEK, University of Freiburg, Freiburg 79110, Germany
Kornelius Nielsch Institute of Nanostructure and Solid State Physics, Universität Hamburg, Hamburg 20355, Germany; and Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Dresden 01171, Germany (Received 18 April 2016; accepted 8 September 2016)
The characterization of nanostructured samples with at least one restricted dimension like thin films or nanowires is challenging but important to understand their structure and transport mechanism and to improve current industrial products and production processes. We report on the development of a chip-based platform to simultaneously measure the in-plane electrical and thermal conductivity, the Seebeck coefficient as well as the Hall constant of a thin film in the temperature range from 120 K up to 450 K and in a magnetic field of up to 1 T. Due to the design of the setup, time consuming preparation steps can be omitted and a nearly simultaneous measurement of the sample properties is achieved. Typical errors caused by different sample compositions, varying sample geometries, and different heat profiles are avoided with the presented measurement method. As a showcase study displaying the validity and accuracy of our system, we present measurements of the thermoelectric properties of a 110 nm Bi87Sb13 thin film in the temperature range from 120 K up to 450 K.
I. INTRODUCTION
Nano-scaled materials, with their considerably different physical properties compared to bulk material, already play an important role in many state of the art industrial applications like opto-electronics, optical coatings, or transistors.1 Consequently, there is a continuously increasing interest for measurement setups dedicated to samples with small geometrical dimensions like thin films and nanowires. Because of the possibility to directly influence the material properties, nanostructuring is also in the focus of interest in many research fields like thermoelectric energy conversion or magnetic data storage. The efficiency of thermoelectric materials is defined by the figure of merit ZT 5 rS2T/k with the electrical conductivity r, the Seebeck coefficient S, the mean Contributing Editor: Terry M. Tritt a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.353
temperature T, and the thermal conductivity k. Therefore, the target of development is to maximize the Seebeck coefficient and electrical conductivity at a low thermal conductivity, what is hampered by the fact, that the thermal and electrical transport mechanisms are partially coupled. A lot of research for thermoelectric bulk materials has al
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