Paper SE+EN-FrM3
Electrical and Thermal Properties and Understanding Interface Chemistry and Structure of Metal-Pnictogen Chalcogenide Interfaces
Friday, November 1, 2013, 9:00 am, Room 203 C
Thermoelectric materials are attractive for realizing eco-friendly solid-state refrigeration, and waste heat recovery and harvesting [1]. In addition to obtaining materials with high thermoelectric figure of merit ZT, it is key to tailor the electrical and thermal properties of interfaces of these materials with metals through control of interface structure and chemistry for high performance device applications [2]. Here, we describe the properties of interfaces comprised of two high figure-of-merit pnictogen chalcogenides, namely, n-Bi2Te3 and p-Sb2Te3 and Cu, Ni, Ti and Ta. Our results show that the thermal interface conductance of structures is insensitive to the majority charge carrier type. Cu shows the highest thermal conductance, which is about tenfold higher than that of the other interfaces studied. However, we find that interfaces of Ni and Ta with p-type materials show more than tenfold higher electrical conductivities than their interfaces with n-type materials. In order to understand these trends, we embarked on a study of the interface chemistry and structure using a combination of Rutherford Backscattering Spectrometry (RBS) and X-Ray Diffractometry (XRD). Our results from XRD analysis show that all the four metals studied tend to form interfacial phase with Tellurium in different stoichiometric amounts. RBS analysis show that just after 150 oC annealing for 30 minutes Cu diffuses significantly in both n-Bi2Te3 and p-Sb2Te3, whereas Ni shows significant compositional changes in p-Sb2Te3 while retaining the multilayer structure with n-Bi2Te3. Ti and Ta maintain multilayer structure with both n-Bi2Te3 and p-Sb2Te3. We will discuss our findings and our inferences of the interface chemistry/structure property relationships. Our results will be important for designing metal contacts to any thermoelectric material based device and especially for applications like spot cooling in electronics chips where interfacial properties have become the bottleneck for realizing high-efficiency thermoelectric cooling.
References
1) S.B. Riffat, and X.L. Ma, "Thermoelectrics: A review of present and potential applications," Applied Thermal Engineering, vol. 23, 2003, pp. 913-935.
2) G. Chen, M.S. Dresselhaus, G. Dresselhaus, J.P. Fleurial, and T. Caillat, "Recent developments in thermoelectric materials," International Materials Reviews, vol. 48, 2003, pp. 45-66.