Multiphase identification in Ni-PbTe contacts by EBSD and aberration-corrected STEM

EBSD in combination with aberration-corrected STEM is used to study the interfacial layer forming at Ni electrode - PbTe thermoelectric material interfaces. Contrary to previous studies, both orthorhombic and monoclinic phases are identified within the interfacial layer. EBSD and STEM data at interphase boundaries demonstrate an approximately smooth transition from orthorhombic to monoclinic phase with almost no crystal defects due to the small differences in lattice parameters and the prevalence of one of two previously unknown orientation relationships between the phases. Moreover, the presence of special boundaries resulting in orientation domains within both phases throughout the interfacial nickel telluride layer needs to be considered when fabricating future thermoelectric devices.