Solid-state nucleation at the interfaces of thin Ni films on CdTe and Hg0.8Cd0.2Te

Abstract

The interfacial reaction between thin Ni film (deposited by either e beam evaporation or sputtering) and (Cd, Hg0.8Cd0.2)Te has been investigated using transmission electron microscopy and diffraction. Auger depth profiles have been used to determine the distribution of Te, Cd, Hg, and Ni with respect to the interface of Ni-Hg1−x CdxTe. In the Ni-Hg0.8Cd0.2Te system, we observed the δ-phase (NiTe-NiTe2) formation upon deposition of 40- and 80-Å Ni films with either deposition system at the as-deposited temperature. The electron diffraction patterns of the δ phase and some Ni were observed, with the formation of the δ phase located at the interface. The electron diffraction of both the Ni film and δ phase were partially ordered with respect to the substrates. The Auger depth profile indicated that the excess of Te appeared mostly at the interface. Annealing of the Ni-Hg0.8 Cd0.2 Te system in a vacuum and at 100, 200, and 300 °C shows growth of the crystal and increased ordering of the δ phase. In the Ni-CdTe system the generation of Te was observed for both sputter deposition and e beam evaporation. Auger profiling indicated that the amount of Te generated by sputtering was approximately three times the amount of Te generated by e beam evaporation. The generated Te was mostly accumulated at the interface of Ni-CdTe. We observed δ-phase formation upon annealing at 250 °C after sputter deposition, and at 300 °C after e beam evaporation of Ni on CdTe substrates, but the crystallites did not have the orientational relation with CdTe substrates (texturing), as was seen in the Ni-Hg0.8 Cd0.2 Te system.