Low Resistance Ohmic Contacts to Bi2Te3 Using Ni and Co Metallization

A detailed study of the impact of surface preparation and postdeposition annealing on contact resistivity for sputtered Ni and Co contacts to thin-film Bi2Te3 is presented. The specific contact resistivity is obtained using the transfer length method. It is observed that in situ sputter cleaning using Ar bombardment before metal deposition gives a surface free of oxides and other contaminants. This surface treatment reduces the contact resistivity by more than 10 times for both Ni and Co contacts. Postdeposition annealing at 100 degrees C on samples that were sputter-cleaned further reduces the contact resistivity to <10(-7) Omega cm(2) for both Ni and Co contacts to Bi2Te3. Co as a suitable contact metal to Bi2Te3 is reported. Co provided similar contact resistance values as Ni, but had better adhesion and less diffusion into the thermoelectric material, making it a suitable candidate for contact metallization to Bi2Te3 based devices. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3385154] All rights reserved.