Atomistic Study of the Electronic Contact Resistivity Between the Half-Heusler Alloys ( HfCoSb, HfZrCoSb and HfZrNiSn ) and the Metal Ag

Half-Heusler(HH) alloys have shown promising thermoelectric properties in the medium and high temperature range. To harness these material properties for thermoelectric applications, it is important to realize electrical contacts with low electrical contact resistivity. However, little is known about the detailed structural and electronic properties of such contacts, and the expected values of contact resistivity. Here, we employ atomistic ab initio calculations to study electrical contacts in a subclass of HH alloys consisting of the compounds HfCoSb, HfZrCoSb, and HfZrNiSn. By using Ag as an example metal, we show that the termination of the HH material critically determines the presence or absence of strong deformations at the interface. We also study the cases of contacts to the p-type and n-type materials, and our results indicate that the p-type materials generally form ohmic contacts while the n-type materials have a small Schottky barrier. We predict the temperature dependence of the contact resistivity as well as quantitative values that set lower limits for these systems.